Repository: angeloc/simplemodbusng
Branch: master
Commit: 1079f442a559
Files: 17
Total size: 119.3 KB
Directory structure:
gitextract_8ia3zrgx/
├── .github/
│ └── FUNDING.yml
├── README.md
├── SimpleModbusMaster/
│ ├── SimpleModbusMaster.cpp
│ ├── SimpleModbusMaster.h
│ ├── examples/
│ │ └── SimpleModbusMasterExample/
│ │ └── SimpleModbusMasterExample.ino
│ └── keywords.txt
├── SimpleModbusMasterSoftwareSerial/
│ ├── SimpleModbusMasterSoftwareSerial.cpp
│ └── SimpleModbusMasterSoftwareSerial.h
├── SimpleModbusSlave/
│ ├── SimpleModbusSlave.cpp
│ ├── SimpleModbusSlave.h
│ ├── examples/
│ │ └── SimpleModbusSlaveExample/
│ │ └── SimpleModbusSlaveExample.ino
│ └── keywords.txt
├── SimpleModbusSlaveSoftwareSerial/
│ ├── SimpleModbusSlaveSoftwareSerial.cpp
│ ├── SimpleModbusSlaveSoftwareSerial.h
│ ├── examples/
│ │ └── SimpleModbusTinyExample/
│ │ └── SimpleModbusTinyExample.ino
│ └── keywords.txt
└── gpl-3.0.txt
================================================
FILE CONTENTS
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================================================
FILE: .github/FUNDING.yml
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custom: https://paypal.me/angelocomp/10
================================================
FILE: README.md
================================================
# SimpleModbus NG
SimpleModbus is a collection of Arduino libraries that enables you to communicate serially using the Modicon Modbus RTU protocol.
This project was born as an updated version of http://code.google.com/p/simple-modbus/ by Bester Juan because it lacks support for commands other than 3 and 16. More important the code is now on github, so you can contribute more easily.
This projects is actively maintained, so feel free to ask for features or reporting bugs!
## Features
This library adds support for command 6 and provides a more extensive support for arduino pins.
The goal of the project is to support all usable MODBUS commands on arduino and expose all arduino pins so you can use an arduino as an advanced automation controller for both analog/digital in/out.
NEW: Support for SoftwareSerial, really useful on AtTiny85. You can find both library and an example that works reliable on attiny85 microcontroller.
## Usage
Simply copy the SimpleModbusMaster or SimpleModbusSlave or both into your Arduino IDE **libraries** folder. Than restart the ide and open the corresponding example into the example_master or example_slave folder.
================================================
FILE: SimpleModbusMaster/SimpleModbusMaster.cpp
================================================
#include "SimpleModbusMaster.h"
#define BUFFER_SIZE 128
// modbus specific exceptions
#define ILLEGAL_FUNCTION 1
#define ILLEGAL_DATA_ADDRESS 2
#define ILLEGAL_DATA_VALUE 3
unsigned char transmission_ready_Flag;
unsigned char messageOkFlag, messageErrFlag;
unsigned char retry_count;
unsigned char TxEnablePin;
// frame[] is used to recieve and transmit packages.
// The maximum number of bytes in a modbus packet is 256 bytes
// This is limited to the serial buffer of 128 bytes
unsigned char frame[BUFFER_SIZE];
unsigned int timeout, polling;
unsigned int T1_5; // inter character time out in microseconds
unsigned int T3_5; // frame delay in microseconds
unsigned long previousTimeout, previousPolling;
unsigned int total_no_of_packets;
Packet* packet; // current packet
// function definitions
void constructPacket();
void checkResponse();
void check_F3_data(unsigned char buffer);
void check_F16_data();
unsigned char getData();
void check_packet_status();
unsigned int calculateCRC(unsigned char bufferSize);
void sendPacket(unsigned char bufferSize);
unsigned int modbus_update(Packet* packets)
{
// Initialize the connection_status variable to the
// total_no_of_packets. This value cannot be used as
// an index (and normally you won't). Returning this
// value to the main skecth informs the user that the
// previously scanned packet has no connection error.
unsigned int connection_status = total_no_of_packets;
if (transmission_ready_Flag) {
static unsigned int packet_index;
unsigned int failed_connections = 0;
unsigned char current_connection;
do {
if (packet_index == total_no_of_packets) // wrap around to the beginning
packet_index = 0;
// proceed to the next packet
packet = &packets[packet_index];
// get the current connection status
current_connection = packet->connection;
if (!current_connection) {
connection_status = packet_index;
// If all the connection attributes are false return
// immediately to the main sketch
if (++failed_connections == total_no_of_packets)
return connection_status;
}
packet_index++;
} while (!current_connection); // while a packet has no connection get the next one
constructPacket();
}
checkResponse();
check_packet_status();
return connection_status;
}
void constructPacket()
{
transmission_ready_Flag = 0; // disable the next transmission
packet->requests++;
frame[0] = packet->id;
frame[1] = packet->function;
frame[2] = packet->address >> 8; // address Hi
frame[3] = packet->address & 0xFF; // address Lo
frame[4] = packet->no_of_registers >> 8; // no_of_registers Hi
frame[5] = packet->no_of_registers & 0xFF; // no_of_registers Lo
unsigned int crc16;
// construct the frame according to the modbus function
if (packet->function == PRESET_MULTIPLE_REGISTERS) {
unsigned char no_of_bytes = packet->no_of_registers * 2;
unsigned char frameSize = 9 + no_of_bytes; // first 7 bytes of the array + 2 bytes CRC+ noOfBytes
frame[6] = no_of_bytes; // number of bytes
unsigned char index = 7; // user data starts at index 7
unsigned int temp;
unsigned char no_of_registers = packet->no_of_registers;
for (unsigned char i = 0; i < no_of_registers; i++) {
temp = packet->register_array[i]; // get the data
frame[index] = temp >> 8;
index++;
frame[index] = temp & 0xFF;
index++;
}
crc16 = calculateCRC(frameSize - 2);
frame[frameSize - 2] = crc16 >> 8; // split crc into 2 bytes
frame[frameSize - 1] = crc16 & 0xFF;
sendPacket(frameSize);
if (packet->id == 0) { // check broadcast id
messageOkFlag = 1; // message successful, there will be no response on a broadcast
previousPolling = millis(); // start the polling delay
}
} else { // READ_HOLDING_REGISTERS is assumed
crc16 = calculateCRC(6); // the first 6 bytes of the frame is used in the CRC calculation
frame[6] = crc16 >> 8; // crc Lo
frame[7] = crc16 & 0xFF; // crc Hi
sendPacket(8); // a request with function 3, 4 & 6 is always 8 bytes in size
}
}
void checkResponse()
{
if (!messageOkFlag && !messageErrFlag) { // check for response
unsigned char buffer = getData();
if (buffer > 0) { // if there's something in the buffer continue
if (frame[0] == packet->id) { // check id returned
// to indicate an exception response a slave will 'OR'
// the requested function with 0x80
if ((frame[1] & 0x80) == 0x80) { // exctract 0x80
// the third byte in the exception response packet is the actual exception
switch (frame[2]) {
case ILLEGAL_FUNCTION:
packet->illegal_function++;
break;
case ILLEGAL_DATA_ADDRESS:
packet->illegal_data_address++;
break;
case ILLEGAL_DATA_VALUE:
packet->illegal_data_value++;
break;
default:
packet->misc_exceptions++;
}
messageErrFlag = 1; // set an error
previousPolling = millis(); // start the polling delay
} else { // the response is valid
if (frame[1] == packet->function) { // check function number returned
// receive the frame according to the modbus function
if (packet->function == PRESET_MULTIPLE_REGISTERS)
check_F16_data();
else // READ_HOLDING_REGISTERS is assumed
check_F3_data(buffer);
} else { // incorrect function number returned
packet->incorrect_function_returned++;
messageErrFlag = 1; // set an error
previousPolling = millis(); // start the polling delay
}
} // check exception response
} else { // incorrect id returned
packet->incorrect_id_returned++;
messageErrFlag = 1; // set an error
previousPolling = millis(); // start the polling delay
}
} // check buffer
} // check message booleans
}
// checks the time out and polling delay and if a message has been recieved succesfully
void check_packet_status()
{
unsigned char pollingFinished = (millis() - previousPolling) > polling;
if (messageOkFlag && pollingFinished) { // if a valid message was recieved and the polling delay has expired clear the flag
messageOkFlag = 0;
packet->successful_requests++; // transaction sent successfully
packet->retries = 0; // if a request was successful reset the retry counter
transmission_ready_Flag = 1;
}
// if an error message was recieved and the polling delay has expired clear the flag
if (messageErrFlag && pollingFinished) {
messageErrFlag = 0; // clear error flag
packet->retries++;
transmission_ready_Flag = 1;
}
// if the timeout delay has past clear the slot number for next request
if (!transmission_ready_Flag && ((millis() - previousTimeout) > timeout)) {
packet->timeout++;
packet->retries++;
transmission_ready_Flag = 1;
}
// if the number of retries have reached the max number of retries
// allowable, stop requesting the specific packet
if (packet->retries == retry_count) {
packet->connection = 0;
packet->retries = 0;
}
if (transmission_ready_Flag) {
// update the total_errors atribute of the
// packet before requesting a new one
packet->total_errors = packet->timeout +
packet->incorrect_id_returned +
packet->incorrect_function_returned +
packet->incorrect_bytes_returned +
packet->checksum_failed +
packet->buffer_errors +
packet->illegal_function +
packet->illegal_data_address +
packet->illegal_data_value;
}
}
void check_F3_data(unsigned char buffer)
{
unsigned char no_of_registers = packet->no_of_registers;
unsigned char no_of_bytes = no_of_registers * 2;
if (frame[2] == no_of_bytes) { // check number of bytes returned
// combine the crc Low & High bytes
unsigned int recieved_crc = ((frame[buffer - 2] << 8) | frame[buffer - 1]);
unsigned int calculated_crc = calculateCRC(buffer - 2);
if (calculated_crc == recieved_crc) { // verify checksum
unsigned char index = 3;
for (unsigned char i = 0; i < no_of_registers; i++) {
// start at the 4th element in the recieveFrame and combine the Lo byte
packet->register_array[i] = (frame[index] << 8) | frame[index + 1];
index += 2;
}
messageOkFlag = 1; // message successful
} else { // checksum failed
packet->checksum_failed++;
messageErrFlag = 1; // set an error
}
// start the polling delay for messageOkFlag & messageErrFlag
previousPolling = millis();
} else { // incorrect number of bytes returned
packet->incorrect_bytes_returned++;
messageErrFlag = 1; // set an error
previousPolling = millis(); // start the polling delay
}
}
void check_F16_data()
{
unsigned int recieved_address = ((frame[2] << 8) | frame[3]);
unsigned int recieved_registers = ((frame[4] << 8) | frame[5]);
unsigned int recieved_crc = ((frame[6] << 8) | frame[7]); // combine the crc Low & High bytes
unsigned int calculated_crc = calculateCRC(6); // only the first 6 bytes are used for crc calculation
// check the whole packet
if (recieved_address == packet->address &&
recieved_registers == packet->no_of_registers &&
recieved_crc == calculated_crc)
messageOkFlag = 1; // message successful
else {
packet->checksum_failed++;
messageErrFlag = 1;
}
// start the polling delay for messageOkFlag & messageErrFlag
previousPolling = millis();
}
// get the serial data from the buffer
unsigned char getData()
{
unsigned char buffer = 0;
unsigned char overflowFlag = 0;
while (Serial.available()) {
// The maximum number of bytes is limited to the serial buffer size of 128 bytes
// If more bytes is received than the BUFFER_SIZE the overflow flag will be set and the
// serial buffer will be red untill all the data is cleared from the receive buffer,
// while the slave is still responding.
if (overflowFlag)
Serial.read();
else {
if (buffer == BUFFER_SIZE)
overflowFlag = 1;
frame[buffer] = Serial.read();
buffer++;
}
delayMicroseconds(T1_5); // inter character time out
}
// The minimum buffer size from a slave can be an exception response of 5 bytes
// If the buffer was partialy filled clear the buffer.
// The maximum number of bytes in a modbus packet is 256 bytes.
// The serial buffer limits this to 128 bytes.
// If the buffer overflows than clear the buffer and set
// a packet error.
if ((buffer > 0 && buffer < 5) || overflowFlag) {
buffer = 0;
packet->buffer_errors++;
messageErrFlag = 1; // set an error
previousPolling = millis(); // start the polling delay
}
return buffer;
}
void modbus_configure(long baud, unsigned int _timeout, unsigned int _polling,
unsigned char _retry_count, unsigned char _TxEnablePin,
Packet* _packet, unsigned int _total_no_of_packets)
{
Serial.begin(baud);
if (_TxEnablePin > 1) {
// pin 0 & pin 1 are reserved for RX/TX. To disable set _TxEnablePin < 2
TxEnablePin = _TxEnablePin;
pinMode(TxEnablePin, OUTPUT);
digitalWrite(TxEnablePin, LOW);
}
// Modbus states that a baud rate higher than 19200 must use a fixed 750 us
// for inter character time out and 1.75 ms for a frame delay.
// For baud rates below 19200 the timeing is more critical and has to be calculated.
// E.g. 9600 baud in a 10 bit packet is 960 characters per second
// In milliseconds this will be 960characters per 1000ms. So for 1 character
// 1000ms/960characters is 1.04167ms per character and finaly modbus states an
// intercharacter must be 1.5T or 1.5 times longer than a normal character and thus
// 1.5T = 1.04167ms * 1.5 = 1.5625ms. A frame delay is 3.5T.
if (baud > 19200) {
T1_5 = 750;
T3_5 = 1750;
} else {
T1_5 = 15000000/baud; // 1T * 1.5 = T1.5
T3_5 = 35000000/baud; // 1T * 3.5 = T3.5
}
// initialize connection status of each packet
for (unsigned char i = 0; i < _total_no_of_packets; i++) {
_packet->connection = 1;
_packet++;
}
// initialize
transmission_ready_Flag = 1;
messageOkFlag = 0;
messageErrFlag = 0;
timeout = _timeout;
polling = _polling;
retry_count = _retry_count;
TxEnablePin = _TxEnablePin;
total_no_of_packets = _total_no_of_packets;
previousTimeout = 0;
previousPolling = 0;
}
unsigned int calculateCRC(unsigned char bufferSize)
{
unsigned int temp, temp2, flag;
temp = 0xFFFF;
for (unsigned char i = 0; i < bufferSize; i++) {
temp = temp ^ frame[i];
for (unsigned char j = 1; j <= 8; j++) {
flag = temp & 0x0001;
temp >>= 1;
if (flag)
temp ^= 0xA001;
}
}
// Reverse byte order.
temp2 = temp >> 8;
temp = (temp << 8) | temp2;
temp &= 0xFFFF;
return temp; // the returned value is already swopped - crcLo byte is first & crcHi byte is last
}
void sendPacket(unsigned char bufferSize)
{
if (TxEnablePin > 1)
digitalWrite(TxEnablePin, HIGH);
for (unsigned char i = 0; i < bufferSize; i++)
Serial.write(frame[i]);
Serial.flush();
// allow a frame delay to indicate end of transmission
delayMicroseconds(T3_5);
if (TxEnablePin > 1)
digitalWrite(TxEnablePin, LOW);
previousTimeout = millis(); // initialize timeout delay
}
================================================
FILE: SimpleModbusMaster/SimpleModbusMaster.h
================================================
#ifndef SIMPLE_MODBUS_MASTER_H
#define SIMPLE_MODBUS_MASTER_H
/*
SimpleModbusMaster allows you to communicate
to any slave using the Modbus RTU protocol.
To communicate with a slave you need to create a
packet that will contain all the information
required to communicate to the slave. There are
numerous counters for easy diagnostic.
These are variables already implemented in a
packet. You can set and clear these variables
as needed.
There are general modbus information counters:
requests - contains the total requests to a slave
successful_requests - contains the total successful requests
total_errors - contains the total errors as a sum
timeout - contains the total time out errors
incorrect_id_returned - contains the total incorrect id returned errors
incorrect_function_returned - contains the total incorrect function returned errors
incorrect_bytes_returned - contains the total incorrect bytes returned errors
checksum_failed - contains the total checksum failed errors
buffer_errors - contains the total buffer errors
And there are modbus specific exception counters:
illegal_function - contains the total illegal_function errors
illegal_data_address - contains the total illegal_data_address errors
illegal_data_value - contains the total illegal_data_value errors
misc_exceptions - contains the total miscellaneous returned exceptions
And finally there is variable called "connection" that
at any given moment contains the current connection
status of the packet. If true then the connection is
active. If false then communication will be stopped
on this packet untill the programmer sets the connections
variable to true explicitly. The reason for this is
because of the time out involved in modbus communication.
EACH faulty slave that's not communicating will slow down
communication on the line with the time out value. E.g.
Using a time out of 1500ms, if you have 10 slaves and 9 of them
stops communicating the latency burden placed on communication
will be 1500ms * 9 = 13,5 seconds!!!!
In addition to this when all the packets are scanned and
all of them have a false connection a value is returned
from modbus_port() to inform you something is wrong with
the port. This is most likely to happen when there is
something physically wrong with the RS485 line.
This is only for information. You have to explicitly set
each packets connection attribute to false.
Packets scanning and communication will automatically
revert to normal.
All the error checking, updating and communication multitasking
takes place in the background!
In general to communicate with to a slave using modbus
RTU you will request information using the specific
slave id, the function request, the starting address
and lastly the number of registers to request.
Function 3 & 16 are supported. In addition to
this broadcasting (id = 0) is supported for function 16.
Constants are provided for:
Function 3 - READ_HOLDING_REGISTERS
Function 16 - PRESET_MULTIPLE_REGISTERS
Note:
The Arduino serial ring buffer is 128 bytes or 64 registers.
Most of the time you will connect the arduino to a master via serial
using a MAX485 or similar.
In a function 3 request the master will attempt to read from your
slave and since 5 bytes is already used for ID, FUNCTION, NO OF BYTES
and two BYTES CRC the master can only request 122 bytes or 61 registers.
In a function 16 request the master will attempt to write to your
slave and since a 9 bytes is already used for ID, FUNCTION, ADDRESS,
NO OF REGISTERS, NO OF BYTES and two BYTES CRC the master can only write
118 bytes or 59 registers.
Using the FTDI USB to Serial converter the maximum bytes you can send is limited
to its internal buffer which is 60 bytes or 30 unsigned int registers.
Thus:
In a function 3 request the master will attempt to read from your
slave and since 5 bytes is already used for ID, FUNCTION, NO OF BYTES
and two BYTES CRC the master can only request 54 bytes or 27 registers.
In a function 16 request the master will attempt to write to your
slave and since a 9 bytes is already used for ID, FUNCTION, ADDRESS,
NO OF REGISTERS, NO OF BYTES and two BYTES CRC the master can only write
50 bytes or 25 registers.
Since it is assumed that you will mostly use the Arduino to connect to a
master without using a USB to Serial converter the internal buffer is set
the same as the Arduino Serial ring buffer which is 128 bytes.
*/
#include "Arduino.h"
#define READ_HOLDING_REGISTERS 3
#define PRESET_MULTIPLE_REGISTERS 16
typedef struct {
// specific packet info
unsigned char id;
unsigned char function;
unsigned int address;
unsigned int no_of_registers;
unsigned int* register_array;
// modbus information counters
unsigned int requests;
unsigned int successful_requests;
unsigned long total_errors;
unsigned int retries;
unsigned int timeout;
unsigned int incorrect_id_returned;
unsigned int incorrect_function_returned;
unsigned int incorrect_bytes_returned;
unsigned int checksum_failed;
unsigned int buffer_errors;
// modbus specific exception counters
unsigned int illegal_function;
unsigned int illegal_data_address;
unsigned int illegal_data_value;
unsigned char misc_exceptions;
// connection status of packet
unsigned char connection;
} Packet;
typedef Packet* packetPointer;
// function definitions
unsigned int modbus_update(Packet* packets);
void modbus_configure(long baud, unsigned int _timeout, unsigned int _polling,
unsigned char _retry_count, unsigned char _TxEnablePin,
Packet* packets, unsigned int _total_no_of_packets);
#endif
================================================
FILE: SimpleModbusMaster/examples/SimpleModbusMasterExample/SimpleModbusMasterExample.ino
================================================
#include <SimpleModbusMaster.h>
/* To communicate with a slave you need to create a
packet that will contain all the information
required to communicate to that slave.
There are numerous counters for easy diagnostic.
These are variables already implemented in a
packet. You can set and clear these variables
as needed.
There are general modbus information counters:
requests - contains the total requests to a slave
successful_requests - contains the total successful requests
total_errors - contains the total errors as a sum
timeout - contains the total time out errors
incorrect_id_returned - contains the total incorrect id returned errors
incorrect_function_returned - contains the total incorrect function returned errors
incorrect_bytes_returned - contains the total incorrect bytes returned errors
checksum_failed - contains the total checksum failed errors
buffer_errors - contains the total buffer errors
And there are modbus specific exception counters:
illegal_function - contains the total illegal function errors
illegal_data_address - contains the total illegal data_address errors
illegal_data_value - contains the total illegal data value errors
misc_exceptions - contains the total miscellaneous returned exceptions
And finally there is a variable called "connection" that
at any given moment contains the current connection
status of the packet. If true then the connection is
active if false then communication will be stopped
on this packet untill the programmer sets the "connection"
variable to true explicitly. The reason for this is
because of the time out involved in modbus communication.
EACH faulty slave that's not communicating will slow down
communication on the line with the time out value. E.g.
Using a time out of 1500ms, if you have 10 slaves and 9 of them
stops communicating the latency burden placed on communication
will be 1500ms * 9 = 13,5 seconds!!!!
modbus_update() returns the previously scanned false connection.
You can use this as the index to your packet array to find out
if the connection has failed in that packet and then react to it.
You can then try to re-enable the connecion by setting the
packet->connection attribute to true.
The index will only be available for one loop cycle, after that
it's cleared and ready to return the next false connection index
if there is one else it will return the packet array size indicating
everything is ok.
All the error checking, updating and communication multitasking
takes place in the background!
In general to communicate with to a slave using modbus
RTU you will request information using the specific
slave id, the function request, the starting address
and lastly the number of registers to request.
Function 3 and 16 are supported. In addition to
this broadcasting (id = 0) is supported on function 16.
Constants are provided for:
Function 3 - READ_HOLDING_REGISTERS
Function 16 - PRESET_MULTIPLE_REGISTERS
The example sketch will read a packet consisting
of 9 registers from address 0 using function 3 from
the SimpleModbusSlave example and then write
another packet containing a value to toggle the led.s
*/
// led to indicate that a communication error is present
#define connection_error_led 13
//////////////////// Port information ///////////////////
#define baud 115200
#define timeout 1000
#define polling 200 // the scan rate
// If the packets internal retry register matches
// the set retry count then communication is stopped
// on that packet. To re-enable the packet you must
// set the "connection" variable to true.
#define retry_count 10
// used to toggle the receive/transmit pin on the driver
#define TxEnablePin 2
// This is the easiest way to create new packets
// Add as many as you want. TOTAL_NO_OF_PACKETS
// is automatically updated.
enum {
PACKET1,
PACKET2,
// leave this last entry
TOTAL_NO_OF_PACKETS
};
// Create an array of Packets for modbus_update()
Packet packets[TOTAL_NO_OF_PACKETS];
// Create a packetPointer to access each packet
// individually. This is not required you can access
// the array explicitly. E.g. packets[PACKET1].id = 2;
// This does become tedious though...
packetPointer packet1 = &packets[PACKET1];
packetPointer packet2 = &packets[PACKET2];
// The data from the PLC will be stored
// in the regs array
unsigned int regs[9];
unsigned int write_regs[1];
unsigned long last_toggle = 0;
void setup()
{
// read 3 registers starting at address 0
packet1->id = 2;
packet1->function = READ_HOLDING_REGISTERS;
packet1->address = 0;
packet1->no_of_registers = 9;
packet1->register_array = regs;
// write the 9 registers to the PLC starting at address 3
packet2->id = 2;
packet2->function = PRESET_MULTIPLE_REGISTERS;
packet2->address = 6;
packet2->no_of_registers = 1;
packet2->register_array = write_regs;
// Initialize communication settings etc...
modbus_configure(baud, timeout, polling, retry_count, TxEnablePin, packets, TOTAL_NO_OF_PACKETS);
pinMode(connection_error_led, OUTPUT);
}
void loop()
{
unsigned int connection_status = modbus_update(packets);
if (millis() - last_toggle > 1000) {
last_toggle = millis();
write_regs[0] = led_on;
}
if (connection_status != TOTAL_NO_OF_PACKETS) {
digitalWrite(connection_error_led, HIGH);
// You could re-enable the connection by:
//packets[connection_status].connection = true;
} else {
digitalWrite(connection_error_led, LOW);
}
}
================================================
FILE: SimpleModbusMaster/keywords.txt
================================================
Packet KEYWORD1
packetPointer KEYWORD1
modbus_configure KEYWORD2
modbus_port KEYWORD2
###### Constants ######
READ_HOLDING_REGISTERS LITERAL1
PRESET_MULTIPLE_REGISTERS LITERAL1
================================================
FILE: SimpleModbusMasterSoftwareSerial/SimpleModbusMasterSoftwareSerial.cpp
================================================
#include "SimpleModbusMasterSoftwareSerial.h"
#define BUFFER_SIZE 128
// modbus specific exceptions
#define ILLEGAL_FUNCTION 1
#define ILLEGAL_DATA_ADDRESS 2
#define ILLEGAL_DATA_VALUE 3
unsigned char transmission_ready_Flag;
unsigned char messageOkFlag, messageErrFlag;
unsigned char retry_count;
unsigned char TxEnablePin;
// frame[] is used to recieve and transmit packages.
// The maximum number of bytes in a modbus packet is 256 bytes
// This is limited to the serial buffer of 128 bytes
unsigned char frame[BUFFER_SIZE];
unsigned int timeout, polling;
unsigned int T1_5; // inter character time out in microseconds
unsigned int T3_5; // frame delay in microseconds
unsigned long previousTimeout, previousPolling;
unsigned int total_no_of_packets;
Packet* packet; // current packet
SoftwareSerial* _port;
// function definitions
void constructPacket();
void checkResponse();
void check_F3_data(unsigned char buffer);
void check_F16_data();
unsigned char getData();
void check_packet_status();
unsigned int calculateCRC(unsigned char bufferSize);
void sendPacket(unsigned char bufferSize);
// use this function create packets
void modbus_packet_init(Packet *packet, unsigned char id, unsigned char function, unsigned int dest_register, unsigned int num_registers, unsigned int *reg) {
packet->id = id;
packet->function = function;
packet->address = dest_register; // first slave register to write to
packet->no_of_registers = num_registers; // number of registers to write
packet->register_array = reg; // first master register to read from
}
unsigned int modbus_update(Packet* packets)
{
// Initialize the connection_status variable to the
// total_no_of_packets. This value cannot be used as
// an index (and normally you won't). Returning this
// value to the main skecth informs the user that the
// previously scanned packet has no connection error.
unsigned int connection_status = total_no_of_packets;
if (transmission_ready_Flag)
{
static unsigned int packet_index;
unsigned int failed_connections = 0;
unsigned char current_connection;
do
{
if (packet_index == total_no_of_packets) // wrap around to the beginning
packet_index = 0;
// proceed to the next packet
packet = &packets[packet_index];
// get the current connection status
current_connection = packet->connection;
if (!current_connection)
{
connection_status = packet_index;
// If all the connection attributes are false return
// immediately to the main sketch
if (++failed_connections == total_no_of_packets)
return connection_status;
}
packet_index++;
}while (!current_connection); // while a packet has no connection get the next one
constructPacket();
}
checkResponse();
check_packet_status();
return connection_status;
}
void constructPacket()
{
unsigned int crc16;
transmission_ready_Flag = 0; // disable the next transmission
packet->requests++;
frame[0] = packet->id;
frame[1] = packet->function;
frame[2] = packet->address >> 8; // address Hi
frame[3] = packet->address & 0xFF; // address Lo
frame[4] = packet->no_of_registers >> 8; // no_of_registers Hi
frame[5] = packet->no_of_registers & 0xFF; // no_of_registers Lo
// construct the frame according to the modbus function
if (packet->function == PRESET_MULTIPLE_REGISTERS)
{
unsigned char no_of_bytes = packet->no_of_registers * 2;
unsigned char frameSize = 9 + no_of_bytes; // first 7 bytes of the array + 2 bytes CRC+ noOfBytes
frame[6] = no_of_bytes; // number of bytes
unsigned char index = 7; // user data starts at index 7
unsigned int temp;
// should be unsigned int but we will never send more than 255 registers in 1 packet
unsigned char no_of_registers = packet->no_of_registers;
for (unsigned char i = 0; i < no_of_registers; i++)
{
temp = packet->register_array[i]; // get the data
frame[index] = temp >> 8;
index++;
frame[index] = temp & 0xFF;
index++;
}
crc16 = calculateCRC(frameSize - 2);
frame[frameSize - 2] = crc16 >> 8; // split crc into 2 bytes
frame[frameSize - 1] = crc16 & 0xFF;
sendPacket(frameSize);
if (packet->id == 0) // check broadcast id
{
messageOkFlag = 1; // message successful, there will be no response on a broadcast
previousPolling = millis(); // start the polling delay
}
}
else // READ_HOLDING_REGISTERS is assumed
{
crc16 = calculateCRC(6); // the first 6 bytes of the frame is used in the CRC calculation
frame[6] = crc16 >> 8; // crc Lo
frame[7] = crc16 & 0xFF; // crc Hi
sendPacket(8); // a request with function 3, 4 & 6 is always 8 bytes in size
}
}
void checkResponse()
{
if (!messageOkFlag && !messageErrFlag) // check for response
{
unsigned char buffer = getData();
if (buffer > 0) // if there's something in the buffer continue
{
if (frame[0] == packet->id) // check id returned
{
// to indicate an exception response a slave will 'OR'
// the requested function with 0x80
if ((frame[1] & 0x80) == 0x80) // exctract 0x80
{
// the third byte in the exception response packet is the actual exception
switch (frame[2])
{
case ILLEGAL_FUNCTION: packet->illegal_function++; break;
case ILLEGAL_DATA_ADDRESS: packet->illegal_data_address++; break;
case ILLEGAL_DATA_VALUE: packet->illegal_data_value++; break;
default: packet->misc_exceptions++;
}
messageErrFlag = 1; // set an error
previousPolling = millis(); // start the polling delay
}
else // the response is valid
{
if (frame[1] == packet->function) // check function number returned
{
// receive the frame according to the modbus function
if (packet->function == PRESET_MULTIPLE_REGISTERS)
check_F16_data();
else // READ_HOLDING_REGISTERS is assumed
check_F3_data(buffer);
}
else // incorrect function number returned
{
packet->incorrect_function_returned++;
messageErrFlag = 1; // set an error
previousPolling = millis(); // start the polling delay
}
} // check exception response
}
else // incorrect id returned
{
packet->incorrect_id_returned++;
messageErrFlag = 1; // set an error
previousPolling = millis(); // start the polling delay
}
} // check buffer
} // check message booleans
}
// checks the time out and polling delay and if a message has been recieved succesfully
void check_packet_status()
{
unsigned char pollingFinished = (millis() - previousPolling) > polling;
// if a valid message was recieved and the polling delay has expired clear the flag
if (messageOkFlag && pollingFinished)
{
messageOkFlag = 0;
packet->successful_requests++; // transaction sent successfully
packet->retries = 0; // if a request was successful reset the retry counter
transmission_ready_Flag = 1;
}
// if an error message was recieved and the polling delay has expired clear the flag
if (messageErrFlag && pollingFinished)
{
messageErrFlag = 0; // clear error flag
packet->retries++;
transmission_ready_Flag = 1;
}
// if the timeout delay has past clear the slot number for next request
if (!transmission_ready_Flag && ((millis() - previousTimeout) > timeout))
{
packet->timeout++;
packet->retries++;
transmission_ready_Flag = 1;
}
// if the number of retries have reached the max number of retries
// allowable, stop requesting the specific packet
if (packet->retries == retry_count)
{
packet->connection = 0;
packet->retries = 0;
}
if (transmission_ready_Flag)
{
// update the total_errors atribute of the
// packet before requesting a new one
packet->total_errors = packet->timeout +
packet->incorrect_id_returned +
packet->incorrect_function_returned +
packet->incorrect_bytes_returned +
packet->checksum_failed +
packet->buffer_errors +
packet->illegal_function +
packet->illegal_data_address +
packet->illegal_data_value;
}
}
void check_F3_data(unsigned char buffer)
{
unsigned char no_of_registers = packet->no_of_registers;
unsigned char no_of_bytes = no_of_registers * 2;
if (frame[2] == no_of_bytes) // check number of bytes returned
{
// combine the crc Low & High bytes
unsigned int recieved_crc = ((frame[buffer - 2] << 8) | frame[buffer - 1]);
unsigned int calculated_crc = calculateCRC(buffer - 2);
if (calculated_crc == recieved_crc) // verify checksum
{
unsigned char index = 3;
for (unsigned char i = 0; i < no_of_registers; i++)
{
// start at the 4th element in the recieveFrame and combine the Lo byte
packet->register_array[i] = (frame[index] << 8) | frame[index + 1];
index += 2;
}
messageOkFlag = 1; // message successful
}
else // checksum failed
{
packet->checksum_failed++;
messageErrFlag = 1; // set an error
}
// start the polling delay for messageOkFlag & messageErrFlag
previousPolling = millis();
}
else // incorrect number of bytes returned
{
packet->incorrect_bytes_returned++;
messageErrFlag = 1; // set an error
previousPolling = millis(); // start the polling delay
}
}
void check_F16_data()
{
unsigned int recieved_address = ((frame[2] << 8) | frame[3]);
unsigned int recieved_registers = ((frame[4] << 8) | frame[5]);
unsigned int recieved_crc = ((frame[6] << 8) | frame[7]); // combine the crc Low & High bytes
unsigned int calculated_crc = calculateCRC(6); // only the first 6 bytes are used for crc calculation
// check the whole packet
if (recieved_address == packet->address &&
recieved_registers == packet->no_of_registers &&
recieved_crc == calculated_crc)
messageOkFlag = 1; // message successful
else
{
packet->checksum_failed++;
messageErrFlag = 1;
}
// start the polling delay for messageOkFlag & messageErrFlag
previousPolling = millis();
}
// get the serial data from the buffer
unsigned char getData()
{
unsigned char buffer = 0;
unsigned char overflowFlag = 0;
while ((*_port).available())
{
// The maximum number of bytes is limited to the serial buffer size of 128 bytes
// If more bytes is received than the BUFFER_SIZE the overflow flag will be set and the
// serial buffer will be red untill all the data is cleared from the receive buffer,
// while the slave is still responding.
if (overflowFlag)
(*_port).read();
else
{
if (buffer == BUFFER_SIZE)
overflowFlag = 1;
frame[buffer] = (*_port).read();
buffer++;
}
delayMicroseconds(T1_5); // inter character time out
}
// The minimum buffer size from a slave can be an exception response of 5 bytes
// If the buffer was partialy filled clear the buffer.
// The maximum number of bytes in a modbus packet is 256 bytes.
// The serial buffer limits this to 128 bytes.
// If the buffer overflows than clear the buffer and set
// a packet error.
if ((buffer > 0 && buffer < 5) || overflowFlag)
{
buffer = 0;
packet->buffer_errors++;
messageErrFlag = 1; // set an error
previousPolling = millis(); // start the polling delay
}
return buffer;
}
void modbus_configure(SoftwareSerial* comPort, long baud,
unsigned int _timeout, unsigned int _polling,
unsigned char _retry_count, unsigned char _TxEnablePin,
Packet* _packet, unsigned int _total_no_of_packets)
{
_port = comPort;
(*_port).begin(baud);
// pin 0 & pin 1 are reserved for RX/TX. To disable set _TxEnablePin < 2
if (_TxEnablePin > 1)
{
TxEnablePin = _TxEnablePin;
pinMode(TxEnablePin, OUTPUT);
digitalWrite(TxEnablePin, LOW);
}
// Modbus states that a baud rate higher than 19200 must use a fixed 750 us
// for inter character time out and 1.75 ms for a frame delay.
// For baud rates below 19200 the timeing is more critical and has to be calculated.
// E.g. 9600 baud in a 10 bit packet is 960 characters per second
// In milliseconds this will be 960characters per 1000ms. So for 1 character
// 1000ms/960characters is 1.04167ms per character and finaly modbus states an
// intercharacter must be 1.5T or 1.5 times longer than a normal character and thus
// 1.5T = 1.04167ms * 1.5 = 1.5625ms. A frame delay is 3.5T.
if (baud > 19200)
{
T1_5 = 750;
T3_5 = 1750;
}
else
{
T1_5 = 15000000/baud; // 1T * 1.5 = T1.5
T3_5 = 35000000/baud; // 1T * 3.5 = T3.5
}
// initialize connection status of each packet
for (unsigned char i = 0; i < _total_no_of_packets; i++)
{
_packet->connection = 1;
_packet++;
}
// initialize
transmission_ready_Flag = 1;
messageOkFlag = 0;
messageErrFlag = 0;
timeout = _timeout;
polling = _polling;
retry_count = _retry_count;
TxEnablePin = _TxEnablePin;
total_no_of_packets = _total_no_of_packets;
previousTimeout = 0;
previousPolling = 0;
}
unsigned int calculateCRC(unsigned char bufferSize)
{
unsigned int temp, temp2, flag;
temp = 0xFFFF;
for (unsigned char i = 0; i < bufferSize; i++)
{
temp = temp ^ frame[i];
for (unsigned char j = 1; j <= 8; j++)
{
flag = temp & 0x0001;
temp >>= 1;
if (flag)
temp ^= 0xA001;
}
}
// Reverse byte order.
temp2 = temp >> 8;
temp = (temp << 8) | temp2;
temp &= 0xFFFF;
return temp; // the returned value is already swopped - crcLo byte is first & crcHi byte is last
}
void sendPacket(unsigned char bufferSize)
{
if (TxEnablePin > 1)
digitalWrite(TxEnablePin, HIGH);
for (unsigned char i = 0; i < bufferSize; i++)
(*_port).write(frame[i]);
// finish writing buffer to the wire, only works for HardwareSerial
(*_port).flush();
// allow a frame delay to indicate end of transmission
delayMicroseconds(T3_5);
if (TxEnablePin > 1)
digitalWrite(TxEnablePin, LOW);
previousTimeout = millis(); // initialize timeout delay
}
================================================
FILE: SimpleModbusMasterSoftwareSerial/SimpleModbusMasterSoftwareSerial.h
================================================
#ifndef SIMPLE_MODBUS_MASTER_H
#define SIMPLE_MODBUS_MASTER_H
/*
SoftwareSerial has limitations and is NOT SUPPORTED ON ALL PINS.
SimpleModbusMaster allows you to communicate
to any slave using the Modbus RTU protocol.
To communicate with a slave you need to create a
packet that will contain all the information
required to communicate to the slave. There are
numerous counters for easy diagnostic.
These are variables already implemented in a
packet. You can set and clear these variables
as needed.
There are general modbus information counters:
requests - contains the total requests to a slave
successful_requests - contains the total successful requests
total_errors - contains the total errors as a sum
timeout - contains the total time out errors
incorrect_id_returned - contains the total incorrect id returned errors
incorrect_function_returned - contains the total incorrect function returned errors
incorrect_bytes_returned - contains the total incorrect bytes returned errors
checksum_failed - contains the total checksum failed errors
buffer_errors - contains the total buffer errors
And there are modbus specific exception counters:
illegal_function - contains the total illegal_function errors
illegal_data_address - contains the total illegal_data_address errors
illegal_data_value - contains the total illegal_data_value errors
misc_exceptions - contains the total miscellaneous returned exceptions
And finally there is variable called "connection" that
at any given moment contains the current connection
status of the packet. If true then the connection is
active. If false then communication will be stopped
on this packet untill the programmer sets the connections
variable to true explicitly. The reason for this is
because of the time out involved in modbus communication.
EACH faulty slave that's not communicating will slow down
communication on the line with the time out value. E.g.
Using a time out of 1500ms, if you have 10 slaves and 9 of them
stops communicating the latency burden placed on communication
will be 1500ms * 9 = 13,5 seconds!!!!
In addition to this when all the packets are scanned and
all of them have a false connection a value is returned
from modbus_port() to inform you something is wrong with
the port. This is most likely to happen when there is
something physically wrong with the RS485 line.
This is only for information. You have to explicitly set
each packets connection attribute to false.
Packets scanning and communication will automatically
revert to normal.
All the error checking, updating and communication multitasking
takes place in the background!
In general to communicate with to a slave using modbus
RTU you will request information using the specific
slave id, the function request, the starting address
and lastly the number of registers to request.
Function 3 & 16 are supported. In addition to
this broadcasting (id = 0) is supported for function 16.
Constants are provided for:
Function 3 - READ_HOLDING_REGISTERS
Function 16 - PRESET_MULTIPLE_REGISTERS
Note:
The Arduino serial ring buffer is 128 bytes or 64 registers.
Most of the time you will connect the arduino to a master via serial
using a MAX485 or similar.
In a function 3 request the master will attempt to read from your
slave and since 5 bytes is already used for ID, FUNCTION, NO OF BYTES
and two BYTES CRC the master can only request 122 bytes or 61 registers.
In a function 16 request the master will attempt to write to your
slave and since a 9 bytes is already used for ID, FUNCTION, ADDRESS,
NO OF REGISTERS, NO OF BYTES and two BYTES CRC the master can only write
118 bytes or 59 registers.
Using the FTDI USB to Serial converter the maximum bytes you can send is limited
to its internal buffer which is 60 bytes or 30 unsigned int registers.
Thus:
In a function 3 request the master will attempt to read from your
slave and since 5 bytes is already used for ID, FUNCTION, NO OF BYTES
and two BYTES CRC the master can only request 54 bytes or 27 registers.
In a function 16 request the master will attempt to write to your
slave and since a 9 bytes is already used for ID, FUNCTION, ADDRESS,
NO OF REGISTERS, NO OF BYTES and two BYTES CRC the master can only write
50 bytes or 25 registers.
Since it is assumed that you will mostly use the Arduino to connect to a
master without using a USB to Serial converter the internal buffer is set
the same as the Arduino Serial ring buffer which is 128 bytes.
*/
#include "Arduino.h"
#include "SoftwareSerial.h"
#define READ_HOLDING_REGISTERS 3
#define PRESET_MULTIPLE_REGISTERS 16
typedef struct
{
// specific packet info
unsigned char id;
unsigned char function;
unsigned int address;
unsigned int no_of_registers;
unsigned int* register_array;
// modbus information counters
unsigned int requests;
unsigned int successful_requests;
unsigned long total_errors;
unsigned int retries;
unsigned int timeout;
unsigned int incorrect_id_returned;
unsigned int incorrect_function_returned;
unsigned int incorrect_bytes_returned;
unsigned int checksum_failed;
unsigned int buffer_errors;
// modbus specific exception counters
unsigned int illegal_function;
unsigned int illegal_data_address;
unsigned int illegal_data_value;
unsigned char misc_exceptions;
// connection status of packet
unsigned char connection;
}Packet;
typedef Packet* packetPointer;
unsigned int modbus_update(Packet* packets);
void modbus_configure(
SoftwareSerial* comPort,
long baud,
unsigned int _timeout,
unsigned int _polling,
unsigned char _retry_count,
unsigned char _TxEnablePin,
Packet* packets,
unsigned int _total_no_of_packets);
void modbus_packet_init(
Packet *packet,
unsigned char id,
unsigned char function,
unsigned int dest_register,
unsigned int num_registers,
unsigned int *reg);
#endif
================================================
FILE: SimpleModbusSlave/SimpleModbusSlave.cpp
================================================
#include "SimpleModbusSlave.h"
#define BUFFER_SIZE 128
// frame[] is used to recieve and transmit packages.
// The maximum serial ring buffer size is 128
unsigned char frame[BUFFER_SIZE];
unsigned int holdingRegsSize; // size of the register array
unsigned char broadcastFlag;
unsigned char slaveID;
unsigned char function;
unsigned char TxEnablePin;
unsigned int errorCount;
unsigned int T1_5; // inter character time out
unsigned int T3_5; // frame delay
// function definitions
void exceptionResponse(unsigned char exception);
unsigned int calculateCRC(unsigned char bufferSize);
void sendPacket(unsigned char bufferSize);
unsigned int modbus_update(unsigned int *holdingRegs)
{
unsigned char buffer = 0;
unsigned char overflow = 0;
while (Serial.available()) {
// The maximum number of bytes is limited to the serial buffer size of 128 bytes
// If more bytes is received than the BUFFER_SIZE the overflow flag will be set and the
// serial buffer will be red untill all the data is cleared from the receive buffer.
if (overflow)
Serial.read();
else {
if (buffer == BUFFER_SIZE)
overflow = 1;
frame[buffer] = Serial.read();
buffer++;
}
delayMicroseconds(T1_5); // inter character time out
}
// If an overflow occurred increment the errorCount
// variable and return to the main sketch without
// responding to the request i.e. force a timeout
if (overflow)
return errorCount++;
// The minimum request packet is 8 bytes for function 3 & 16
if (buffer > 6) {
unsigned char id = frame[0];
broadcastFlag = 0;
if (id == 0)
broadcastFlag = 1;
if (id == slaveID || broadcastFlag) { // if the recieved ID matches the slaveID or broadcasting id (0), continue
unsigned int crc = ((frame[buffer - 2] << 8) | frame[buffer - 1]); // combine the crc Low & High bytes
if (calculateCRC(buffer - 2) == crc) { // if the calculated crc matches the recieved crc continue
function = frame[1];
unsigned int startingAddress = ((frame[2] << 8) | frame[3]); // combine the starting address bytes
unsigned int no_of_registers = ((frame[4] << 8) | frame[5]); // combine the number of register bytes
unsigned int maxData = startingAddress + no_of_registers;
unsigned char index;
unsigned char address;
unsigned int crc16;
// broadcasting is not supported for function 3
if (!broadcastFlag && (function == 3)) {
if (startingAddress < holdingRegsSize) { // check exception 2 ILLEGAL DATA ADDRESS
if (maxData <= holdingRegsSize) { // check exception 3 ILLEGAL DATA VALUE
unsigned char noOfBytes = no_of_registers * 2;
unsigned char responseFrameSize = 5 + noOfBytes; // ID, function, noOfBytes, (dataLo + dataHi) * number of registers, crcLo, crcHi
frame[0] = slaveID;
frame[1] = function;
frame[2] = noOfBytes;
address = 3; // PDU starts at the 4th byte
unsigned int temp;
for (index = startingAddress; index < maxData; index++) {
temp = holdingRegs[index];
frame[address] = temp >> 8; // split the register into 2 bytes
address++;
frame[address] = temp & 0xFF;
address++;
}
crc16 = calculateCRC(responseFrameSize - 2);
frame[responseFrameSize - 2] = crc16 >> 8; // split crc into 2 bytes
frame[responseFrameSize - 1] = crc16 & 0xFF;
sendPacket(responseFrameSize);
} else
exceptionResponse(3); // exception 3 ILLEGAL DATA VALUE
} else
exceptionResponse(2); // exception 2 ILLEGAL DATA ADDRESS
} else if (function == 6) {
if (startingAddress < holdingRegsSize) { // check exception 2 ILLEGAL DATA ADDRESS
unsigned int startingAddress = ((frame[2] << 8) | frame[3]);
unsigned int regStatus = ((frame[4] << 8) | frame[5]);
unsigned char responseFrameSize = 8;
holdingRegs[startingAddress] = regStatus;
crc16 = calculateCRC(responseFrameSize - 2);
frame[responseFrameSize - 2] = crc16 >> 8; // split crc into 2 bytes
frame[responseFrameSize - 1] = crc16 & 0xFF;
sendPacket(responseFrameSize);
} else
exceptionResponse(2); // exception 2 ILLEGAL DATA ADDRESS
} else if (function == 16) {
// check if the recieved number of bytes matches the calculated bytes minus the request bytes
// id + function + (2 * address bytes) + (2 * no of register bytes) + byte count + (2 * CRC bytes) = 9 bytes
if (frame[6] == (buffer - 9)) {
if (startingAddress < holdingRegsSize) { // check exception 2 ILLEGAL DATA ADDRESS
if (maxData <= holdingRegsSize) { // check exception 3 ILLEGAL DATA VALUE
address = 7; // start at the 8th byte in the frame
for (index = startingAddress; index < maxData; index++) {
holdingRegs[index] = ((frame[address] << 8) | frame[address + 1]);
address += 2;
}
// only the first 6 bytes are used for CRC calculation
crc16 = calculateCRC(6);
frame[6] = crc16 >> 8; // split crc into 2 bytes
frame[7] = crc16 & 0xFF;
// a function 16 response is an echo of the first 6 bytes from the request + 2 crc bytes
if (!broadcastFlag) // don't respond if it's a broadcast message
sendPacket(8);
} else
exceptionResponse(3); // exception 3 ILLEGAL DATA VALUE
} else
exceptionResponse(2); // exception 2 ILLEGAL DATA ADDRESS
} else
errorCount++; // corrupted packet
} else
exceptionResponse(1); // exception 1 ILLEGAL FUNCTION
} else // checksum failed
errorCount++;
} // incorrect id
} else if (buffer > 0 && buffer < 8)
errorCount++; // corrupted packet
return errorCount;
}
void exceptionResponse(unsigned char exception)
{
errorCount++; // each call to exceptionResponse() will increment the errorCount
if (!broadcastFlag) { // don't respond if its a broadcast message
frame[0] = slaveID;
frame[1] = (function | 0x80); // set the MSB bit high, informs the master of an exception
frame[2] = exception;
unsigned int crc16 = calculateCRC(3); // ID, function + 0x80, exception code == 3 bytes
frame[3] = crc16 >> 8;
frame[4] = crc16 & 0xFF;
sendPacket(5); // exception response is always 5 bytes ID, function + 0x80, exception code, 2 bytes crc
}
}
void modbus_configure(long baud, unsigned char _slaveID, unsigned char _TxEnablePin, unsigned int _holdingRegsSize, unsigned char _lowLatency)
{
slaveID = _slaveID;
Serial.begin(baud);
if (_TxEnablePin > 1) {
// pin 0 & pin 1 are reserved for RX/TX. To disable set txenpin < 2
TxEnablePin = _TxEnablePin;
pinMode(TxEnablePin, OUTPUT);
digitalWrite(TxEnablePin, LOW);
}
// Modbus states that a baud rate higher than 19200 must use a fixed 750 us
// for inter character time out and 1.75 ms for a frame delay.
// For baud rates below 19200 the timeing is more critical and has to be calculated.
// E.g. 9600 baud in a 10 bit packet is 960 characters per second
// In milliseconds this will be 960characters per 1000ms. So for 1 character
// 1000ms/960characters is 1.04167ms per character and finaly modbus states an
// intercharacter must be 1.5T or 1.5 times longer than a normal character and thus
// 1.5T = 1.04167ms * 1.5 = 1.5625ms. A frame delay is 3.5T.
// Added experimental low latency delays. This makes the implementation
// non-standard but practically it works with all major modbus master implementations.
if (baud == 1000000 && _lowLatency) {
T1_5 = 1;
T3_5 = 10;
} else if (baud >= 115200 && _lowLatency) {
T1_5 = 75;
T3_5 = 175;
} else if (baud > 19200) {
T1_5 = 750;
T3_5 = 1750;
} else {
T1_5 = 15000000/baud; // 1T * 1.5 = T1.5
T3_5 = 35000000/baud; // 1T * 3.5 = T3.5
}
holdingRegsSize = _holdingRegsSize;
errorCount = 0; // initialize errorCount
}
unsigned int calculateCRC(byte bufferSize)
{
unsigned int temp, temp2, flag;
temp = 0xFFFF;
for (unsigned char i = 0; i < bufferSize; i++) {
temp = temp ^ frame[i];
for (unsigned char j = 1; j <= 8; j++) {
flag = temp & 0x0001;
temp >>= 1;
if (flag)
temp ^= 0xA001;
}
}
// Reverse byte order.
temp2 = temp >> 8;
temp = (temp << 8) | temp2;
temp &= 0xFFFF;
return temp; // the returned value is already swopped - crcLo byte is first & crcHi byte is last
}
void sendPacket(unsigned char bufferSize)
{
if (TxEnablePin > 1)
digitalWrite(TxEnablePin, HIGH);
for (unsigned char i = 0; i < bufferSize; i++)
Serial.write(frame[i]);
Serial.flush();
// allow a frame delay to indicate end of transmission
delayMicroseconds(T3_5);
if (TxEnablePin > 1)
digitalWrite(TxEnablePin, LOW);
}
================================================
FILE: SimpleModbusSlave/SimpleModbusSlave.h
================================================
#ifndef SIMPLE_MODBUS_SLAVE_H
#define SIMPLE_MODBUS_SLAVE_H
/*
SimpleModbusSlave allows you to communicate
to any slave using the Modbus RTU protocol.
The crc calculation is based on the work published
by jpmzometa at
http://sites.google.com/site/jpmzometa/arduino-mbrt
By Juan Bester : bester.juan@gmail.com
The functions implemented are functions 3 and 16.
read holding registers and preset multiple registers
of the Modbus RTU Protocol, to be used over the Arduino serial connection.
This implementation DOES NOT fully comply with the Modbus specifications.
Specifically the frame time out have not been implemented according
to Modbus standards. The code does however combine the check for
inter character time out and frame time out by incorporating a maximum
time out allowable when reading from the message stream.
These library of functions are designed to enable a program send and
receive data from a device that communicates using the Modbus protocol.
SimpleModbusSlave implements an unsigned int return value on a call to modbus_update().
This value is the total error count since the slave started. It's useful for fault finding.
This code is for a Modbus slave implementing functions 3 and 16
function 3: Reads the binary contents of holding registers (4X references)
function 16: Presets values into a sequence of holding registers (4X references)
All the functions share the same register array.
Exception responses:
1 ILLEGAL FUNCTION
2 ILLEGAL DATA ADDRESS
3 ILLEGAL DATA VALUE
Note:
The Arduino serial ring buffer is 128 bytes or 64 registers.
Most of the time you will connect the arduino to a master via serial
using a MAX485 or similar.
In a function 3 request the master will attempt to read from your
slave and since 5 bytes is already used for ID, FUNCTION, NO OF BYTES
and two BYTES CRC the master can only request 122 bytes or 61 registers.
In a function 16 request the master will attempt to write to your
slave and since a 9 bytes is already used for ID, FUNCTION, ADDRESS,
NO OF REGISTERS, NO OF BYTES and two BYTES CRC the master can only write
118 bytes or 59 registers.
Using the FTDI converter ic the maximum bytes you can send is limited
to its internal buffer which is 60 bytes or 30 unsigned int registers.
Thus:
In a function 3 request the master will attempt to read from your
slave and since 5 bytes is already used for ID, FUNCTION, NO OF BYTES
and two BYTES CRC the master can only request 54 bytes or 27 registers.
In a function 16 request the master will attempt to write to your
slave and since a 9 bytes is already used for ID, FUNCTION, ADDRESS,
NO OF REGISTERS, NO OF BYTES and two BYTES CRC the master can only write
50 bytes or 25 registers.
Since it is assumed that you will mostly use the Arduino to connect to a
master without using a USB to Serial converter the internal buffer is set
the same as the Arduino Serial ring buffer which is 128 bytes.
The functions included here have been derived from the
Modbus Specifications and Implementation Guides
http://www.modbus.org/docs/Modbus_over_serial_line_V1_02.pdf
http://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b.pdf
http://www.modbus.org/docs/PI_MBUS_300.pdf
*/
#include "Arduino.h"
// function definitions
void modbus_configure(long baud, byte _slaveID, byte _TxEnablePin, unsigned int _holdingRegsSize, unsigned char _lowLatency);
unsigned int modbus_update(unsigned int *holdingRegs);
#endif
================================================
FILE: SimpleModbusSlave/examples/SimpleModbusSlaveExample/SimpleModbusSlaveExample.ino
================================================
#include <SimpleModbusSlave.h>
#define ledPin 13 // onboard led
#define buttonPin 7 // push button
/* This example code has 9 holding registers. 6 analogue inputs, 1 button, 1 digital output
and 1 register to indicate errors encountered since started.
Function 5 (write single coil) is not implemented so I'm using a whole register
and function 16 to set the onboard Led on the Atmega328P.
The modbus_update() method updates the holdingRegs register array and checks communication.
Note:
The Arduino serial ring buffer is 128 bytes or 64 registers.
Most of the time you will connect the arduino to a master via serial
using a MAX485 or similar.
In a function 3 request the master will attempt to read from your
slave and since 5 bytes is already used for ID, FUNCTION, NO OF BYTES
and two BYTES CRC the master can only request 122 bytes or 61 registers.
In a function 16 request the master will attempt to write to your
slave and since a 9 bytes is already used for ID, FUNCTION, ADDRESS,
NO OF REGISTERS, NO OF BYTES and two BYTES CRC the master can only write
118 bytes or 59 registers.
Using the FTDI USB to Serial converter the maximum bytes you can send is limited
to its internal buffer which is 60 bytes or 30 unsigned int registers.
Thus:
In a function 3 request the master will attempt to read from your
slave and since 5 bytes is already used for ID, FUNCTION, NO OF BYTES
and two BYTES CRC the master can only request 54 bytes or 27 registers.
In a function 16 request the master will attempt to write to your
slave and since a 9 bytes is already used for ID, FUNCTION, ADDRESS,
NO OF REGISTERS, NO OF BYTES and two BYTES CRC the master can only write
50 bytes or 25 registers.
Since it is assumed that you will mostly use the Arduino to connect to a
master without using a USB to Serial converter the internal buffer is set
the same as the Arduino Serial ring buffer which is 128 bytes.
*/
// Using the enum instruction allows for an easy method for adding and
// removing registers. Doing it this way saves you #defining the size
// of your slaves register array each time you want to add more registers
// and at a glimpse informs you of your slaves register layout.
//////////////// registers of your slave ///////////////////
enum {
// just add or remove registers and you're good to go...
// The first register starts at address 0
ADC0,
ADC1,
ADC2,
ADC3,
ADC4,
ADC5,
LED_STATE,
BUTTON_STATE,
TOTAL_ERRORS,
// leave this one
TOTAL_REGS_SIZE
// total number of registers for function 3 and 16 share the same register array
};
unsigned int holdingRegs[TOTAL_REGS_SIZE]; // function 3 and 16 register array
////////////////////////////////////////////////////////////
void setup()
{
/* parameters(long baudrate,
unsigned char ID,
unsigned char transmit enable pin,
unsigned int holding registers size,
unsigned char low latency)
The transmit enable pin is used in half duplex communication to activate a MAX485 or similar
to deactivate this mode use any value < 2 because 0 & 1 is reserved for Rx & Tx.
Low latency delays makes the implementation non-standard
but practically it works with all major modbus master implementations.
*/
modbus_configure(115200, 2, 2, TOTAL_REGS_SIZE, 0);
pinMode(ledPin, OUTPUT);
pinMode(buttonPin, INPUT);
}
void loop()
{
// modbus_update() is the only method used in loop(). It returns the total error
// count since the slave started. You don't have to use it but it's useful
// for fault finding by the modbus master.
holdingRegs[TOTAL_ERRORS] = modbus_update(holdingRegs);
for (byte i = 0; i < 6; i++) {
holdingRegs[i] = analogRead(i);
delayMicroseconds(50);
}
byte buttonState = digitalRead(buttonPin); // read button states
// assign the buttonState value to the holding register
holdingRegs[BUTTON_STATE] = buttonState;
// read the LED_STATE register value and set the onboard LED high or low with function 16
byte ledState = holdingRegs[LED_STATE];
if (ledState) // set led
digitalWrite(ledPin, HIGH);
if (ledState == 0) { // reset led
digitalWrite(ledPin, LOW);
}
}
================================================
FILE: SimpleModbusSlave/keywords.txt
================================================
modbus_configure KEYWORD2
modbus_update KEYWORD2
================================================
FILE: SimpleModbusSlaveSoftwareSerial/SimpleModbusSlaveSoftwareSerial.cpp
================================================
#include "SimpleModbusSlaveSoftwareSerial.h"
#define BUFFER_SIZE 128
// frame[] is used to recieve and transmit packages.
// The maximum serial ring buffer size is 128
unsigned char frame[BUFFER_SIZE];
unsigned int holdingRegsSize; // size of the register array
unsigned char broadcastFlag;
unsigned char slaveID;
unsigned char function;
unsigned char TxEnablePin;
unsigned int errorCount;
unsigned int T1_5; // inter character time out
unsigned int T3_5; // frame delay
SoftwareSerial* _port;
// function definitions
void exceptionResponse(unsigned char exception);
unsigned int calculateCRC(unsigned char bufferSize);
void sendPacket(unsigned char bufferSize);
unsigned int modbus_update(unsigned int *holdingRegs)
{
unsigned char buffer = 0;
unsigned char overflow = 0;
while ((*_port).available()) {
// The maximum number of bytes is limited to the serial buffer size of 128 bytes
// If more bytes is received than the BUFFER_SIZE the overflow flag will be set and the
// serial buffer will be red untill all the data is cleared from the receive buffer.
if (overflow)
(*_port).read();
else {
if (buffer == BUFFER_SIZE)
overflow = 1;
frame[buffer] = (*_port).read();
buffer++;
}
delayMicroseconds(T1_5); // inter character time out
}
// If an overflow occurred increment the errorCount
// variable and return to the main sketch without
// responding to the request i.e. force a timeout
if (overflow)
return errorCount++;
// The minimum request packet is 8 bytes for function 3 & 16
if (buffer > 6) {
unsigned char id = frame[0];
broadcastFlag = 0;
if (id == 0)
broadcastFlag = 1;
if (id == slaveID || broadcastFlag) { // if the recieved ID matches the slaveID or broadcasting id (0), continue
unsigned int crc = ((frame[buffer - 2] << 8) | frame[buffer - 1]); // combine the crc Low & High bytes
if (calculateCRC(buffer - 2) == crc) { // if the calculated crc matches the recieved crc continue
function = frame[1];
unsigned int startingAddress = ((frame[2] << 8) | frame[3]); // combine the starting address bytes
unsigned int no_of_registers = ((frame[4] << 8) | frame[5]); // combine the number of register bytes
unsigned int maxData = startingAddress + no_of_registers;
unsigned char index;
unsigned char address;
unsigned int crc16;
// broadcasting is not supported for function 3
if (!broadcastFlag && (function == 3)) {
if (startingAddress < holdingRegsSize) { // check exception 2 ILLEGAL DATA ADDRESS
if (maxData <= holdingRegsSize) { // check exception 3 ILLEGAL DATA VALUE
unsigned char noOfBytes = no_of_registers * 2;
unsigned char responseFrameSize = 5 + noOfBytes; // ID, function, noOfBytes, (dataLo + dataHi) * number of registers, crcLo, crcHi
frame[0] = slaveID;
frame[1] = function;
frame[2] = noOfBytes;
address = 3; // PDU starts at the 4th byte
unsigned int temp;
for (index = startingAddress; index < maxData; index++) {
temp = holdingRegs[index];
frame[address] = temp >> 8; // split the register into 2 bytes
address++;
frame[address] = temp & 0xFF;
address++;
}
crc16 = calculateCRC(responseFrameSize - 2);
frame[responseFrameSize - 2] = crc16 >> 8; // split crc into 2 bytes
frame[responseFrameSize - 1] = crc16 & 0xFF;
sendPacket(responseFrameSize);
} else
exceptionResponse(3); // exception 3 ILLEGAL DATA VALUE
} else
exceptionResponse(2); // exception 2 ILLEGAL DATA ADDRESS
} else if (function == 6) {
if (startingAddress < holdingRegsSize) { // check exception 2 ILLEGAL DATA ADDRESS
unsigned int startingAddress = ((frame[2] << 8) | frame[3]);
unsigned int regStatus = ((frame[4] << 8) | frame[5]);
unsigned char responseFrameSize = 8;
holdingRegs[startingAddress] = regStatus;
crc16 = calculateCRC(responseFrameSize - 2);
frame[responseFrameSize - 2] = crc16 >> 8; // split crc into 2 bytes
frame[responseFrameSize - 1] = crc16 & 0xFF;
sendPacket(responseFrameSize);
} else
exceptionResponse(2); // exception 2 ILLEGAL DATA ADDRESS
} else if (function == 16) {
// check if the recieved number of bytes matches the calculated bytes minus the request bytes
// id + function + (2 * address bytes) + (2 * no of register bytes) + byte count + (2 * CRC bytes) = 9 bytes
if (frame[6] == (buffer - 9)) {
if (startingAddress < holdingRegsSize) { // check exception 2 ILLEGAL DATA ADDRESS
if (maxData <= holdingRegsSize) { // check exception 3 ILLEGAL DATA VALUE
address = 7; // start at the 8th byte in the frame
for (index = startingAddress; index < maxData; index++) {
holdingRegs[index] = ((frame[address] << 8) | frame[address + 1]);
address += 2;
}
// only the first 6 bytes are used for CRC calculation
crc16 = calculateCRC(6);
frame[6] = crc16 >> 8; // split crc into 2 bytes
frame[7] = crc16 & 0xFF;
// a function 16 response is an echo of the first 6 bytes from the request + 2 crc bytes
if (!broadcastFlag) // don't respond if it's a broadcast message
sendPacket(8);
} else
exceptionResponse(3); // exception 3 ILLEGAL DATA VALUE
} else
exceptionResponse(2); // exception 2 ILLEGAL DATA ADDRESS
} else
errorCount++; // corrupted packet
} else
exceptionResponse(1); // exception 1 ILLEGAL FUNCTION
} else // checksum failed
errorCount++;
} // incorrect id
} else if (buffer > 0 && buffer < 8)
errorCount++; // corrupted packet
return errorCount;
}
void exceptionResponse(unsigned char exception)
{
errorCount++; // each call to exceptionResponse() will increment the errorCount
if (!broadcastFlag) { // don't respond if its a broadcast message
frame[0] = slaveID;
frame[1] = (function | 0x80); // set the MSB bit high, informs the master of an exception
frame[2] = exception;
unsigned int crc16 = calculateCRC(3); // ID, function + 0x80, exception code == 3 bytes
frame[3] = crc16 >> 8;
frame[4] = crc16 & 0xFF;
sendPacket(5); // exception response is always 5 bytes ID, function + 0x80, exception code, 2 bytes crc
}
}
void modbus_configure(SoftwareSerial* comPort, long baud, unsigned char _slaveID, unsigned char _TxEnablePin, unsigned int _holdingRegsSize)
{
_port = comPort;
slaveID = _slaveID;
(*_port).begin(baud);
if (_TxEnablePin > 1) {
// pin 0 & pin 1 are reserved for RX/TX. To disable set txenpin < 2
TxEnablePin = _TxEnablePin;
pinMode(TxEnablePin, OUTPUT);
digitalWrite(TxEnablePin, LOW);
}
// Modbus states that a baud rate higher than 19200 must use a fixed 750 us
// for inter character time out and 1.75 ms for a frame delay.
// For baud rates below 19200 the timeing is more critical and has to be calculated.
// E.g. 9600 baud in a 10 bit packet is 960 characters per second
// In milliseconds this will be 960characters per 1000ms. So for 1 character
// 1000ms/960characters is 1.04167ms per character and finaly modbus states an
// intercharacter must be 1.5T or 1.5 times longer than a normal character and thus
// 1.5T = 1.04167ms * 1.5 = 1.5625ms. A frame delay is 3.5T.
if (baud > 19200) {
T1_5 = 150;
T3_5 = 350;
} else {
T1_5 = 15000000/baud; // 1T * 1.5 = T1.5
T3_5 = 35000000/baud; // 1T * 3.5 = T3.5
}
holdingRegsSize = _holdingRegsSize;
errorCount = 0; // initialize errorCount
}
unsigned int calculateCRC(byte bufferSize)
{
unsigned int temp, temp2, flag;
temp = 0xFFFF;
for (unsigned char i = 0; i < bufferSize; i++) {
temp = temp ^ frame[i];
for (unsigned char j = 1; j <= 8; j++) {
flag = temp & 0x0001;
temp >>= 1;
if (flag)
temp ^= 0xA001;
}
}
// Reverse byte order.
temp2 = temp >> 8;
temp = (temp << 8) | temp2;
temp &= 0xFFFF;
return temp; // the returned value is already swopped - crcLo byte is first & crcHi byte is last
}
void sendPacket(unsigned char bufferSize)
{
if (TxEnablePin > 1)
digitalWrite(TxEnablePin, HIGH);
for (unsigned char i = 0; i < bufferSize; i++)
(*_port).write(frame[i]);
(*_port).flush();
// allow a frame delay to indicate end of transmission
delayMicroseconds(T3_5);
if (TxEnablePin > 1)
digitalWrite(TxEnablePin, LOW);
}
================================================
FILE: SimpleModbusSlaveSoftwareSerial/SimpleModbusSlaveSoftwareSerial.h
================================================
#ifndef SIMPLE_MODBUS_SLAVE_H
#define SIMPLE_MODBUS_SLAVE_H
/*
SimpleModbusSlave allows you to communicate
to any slave using the Modbus RTU protocol.
The crc calculation is based on the work published
by jpmzometa at
http://sites.google.com/site/jpmzometa/arduino-mbrt
By Juan Bester : bester.juan@gmail.com
The functions implemented are functions 3 and 16.
read holding registers and preset multiple registers
of the Modbus RTU Protocol, to be used over the Arduino serial connection.
This implementation DOES NOT fully comply with the Modbus specifications.
Specifically the frame time out have not been implemented according
to Modbus standards. The code does however combine the check for
inter character time out and frame time out by incorporating a maximum
time out allowable when reading from the message stream.
These library of functions are designed to enable a program send and
receive data from a device that communicates using the Modbus protocol.
SimpleModbusSlave implements an unsigned int return value on a call to modbus_update().
This value is the total error count since the slave started. It's useful for fault finding.
This code is for a Modbus slave implementing functions 3 and 16
function 3: Reads the binary contents of holding registers (4X references)
function 16: Presets values into a sequence of holding registers (4X references)
All the functions share the same register array.
Exception responses:
1 ILLEGAL FUNCTION
2 ILLEGAL DATA ADDRESS
3 ILLEGAL DATA VALUE
Note:
The Arduino serial ring buffer is 128 bytes or 64 registers.
Most of the time you will connect the arduino to a master via serial
using a MAX485 or similar.
In a function 3 request the master will attempt to read from your
slave and since 5 bytes is already used for ID, FUNCTION, NO OF BYTES
and two BYTES CRC the master can only request 122 bytes or 61 registers.
In a function 16 request the master will attempt to write to your
slave and since a 9 bytes is already used for ID, FUNCTION, ADDRESS,
NO OF REGISTERS, NO OF BYTES and two BYTES CRC the master can only write
118 bytes or 59 registers.
Using the FTDI converter ic the maximum bytes you can send is limited
to its internal buffer which is 60 bytes or 30 unsigned int registers.
Thus:
In a function 3 request the master will attempt to read from your
slave and since 5 bytes is already used for ID, FUNCTION, NO OF BYTES
and two BYTES CRC the master can only request 54 bytes or 27 registers.
In a function 16 request the master will attempt to write to your
slave and since a 9 bytes is already used for ID, FUNCTION, ADDRESS,
NO OF REGISTERS, NO OF BYTES and two BYTES CRC the master can only write
50 bytes or 25 registers.
Since it is assumed that you will mostly use the Arduino to connect to a
master without using a USB to Serial converter the internal buffer is set
the same as the Arduino Serial ring buffer which is 128 bytes.
The functions included here have been derived from the
Modbus Specifications and Implementation Guides
http://www.modbus.org/docs/Modbus_over_serial_line_V1_02.pdf
http://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b.pdf
http://www.modbus.org/docs/PI_MBUS_300.pdf
*/
#include "Arduino.h"
#include "SoftwareSerial.h"
// function definitions
void modbus_configure(SoftwareSerial* comPort, long baud, unsigned char _slaveID, unsigned char _TxEnablePin, unsigned int _holdingRegsSize);
unsigned int modbus_update(unsigned int *holdingRegs);
#endif
================================================
FILE: SimpleModbusSlaveSoftwareSerial/examples/SimpleModbusTinyExample/SimpleModbusTinyExample.ino
================================================
#include <SoftwareSerial.h>
#include <SimpleModbusSlaveSoftwareSerial.h>
#define buttonPin0 2 // push button
#define buttonPin1 3 // push button
/* This example code has 2 holding registers. 2 buttons,
and 1 register to indicate errors encountered since started.
The modbus_update() method updates the holdingRegs register array
and checks communication.
Note:
The Arduino serial ring buffer is 128 bytes or 64 registers.
Most of the time you will connect the arduino to a master via serial
using a MAX485 or similar.
In a function 3 request the master will attempt to read from your
slave and since 5 bytes is already used for ID, FUNCTION, NO OF BYTES
and two BYTES CRC the master can only request 122 bytes or 61 registers.
In a function 16 request the master will attempt to write to your
slave and since a 9 bytes is already used for ID, FUNCTION, ADDRESS,
NO OF REGISTERS, NO OF BYTES and two BYTES CRC the master can only write
118 bytes or 59 registers.
Using the FTDI USB to Serial converter the maximum bytes you can send is limited
to its internal buffer which is 60 bytes or 30 unsigned int registers.
Thus:
In a function 3 request the master will attempt to read from your
slave and since 5 bytes is already used for ID, FUNCTION, NO OF BYTES
and two BYTES CRC the master can only request 54 bytes or 27 registers.
In a function 16 request the master will attempt to write to your
slave and since a 9 bytes is already used for ID, FUNCTION, ADDRESS,
NO OF REGISTERS, NO OF BYTES and two BYTES CRC the master can only write
50 bytes or 25 registers.
Since it is assumed that you will mostly use the Arduino to connect to a
master without using a USB to Serial converter the internal buffer is set
the same as the Arduino Serial ring buffer which is 128 bytes.
*/
// Using the enum instruction allows for an easy method for adding and
// removing registers. Doing it this way saves you #defining the size
// of your slaves register array each time you want to add more registers
// and at a glimpse informs you of your slaves register layout.
//////////////// registers of your slave ///////////////////
enum {
// just add or remove registers and your good to go...
// The first register starts at address 0
BUTTON0,
BUTTON1,
TOTAL_ERRORS,
// leave this one
TOTAL_REGS_SIZE
// total number of registers for function 3 and 16 share the same register array
};
unsigned int holdingRegs[TOTAL_REGS_SIZE]; // function 3 and 16 register array
////////////////////////////////////////////////////////////
#define RX 0 // Arduino defined pin (PB0, package pin #5)
#define TX 1 // Arduino defined pin (PB1, package pin #6)
#define RS485_EN 2 // pin to set transmission mode on RS485 chip (PB2, package pin #7)
#define BAUD_RATE 115200 // baud rate for serial communication
#define deviceID 3 // this device address
SoftwareSerial mySerial(RX, TX);
void setup()
{
/* parameters(
SoftwareSerial* comPort
long baudrate,
unsigned char ID,
unsigned char transmit enable pin,
unsigned int holding registers size)
The transmit enable pin is used in half duplex communication to activate a MAX485 or similar
to deactivate this mode use any value < 2 because 0 & 1 is reserved for Rx & Tx
*/
modbus_configure(&mySerial, BAUD_RATE, deviceID, RS485_EN, TOTAL_REGS_SIZE);
pinMode(buttonPin0, INPUT);
pinMode(buttonPin1, INPUT);
}
void loop()
{
// modbus_update() is the only method used in loop(). It returns the total error
// count since the slave started. You don't have to use it but it's useful
// for fault finding by the modbus master.
holdingRegs[TOTAL_ERRORS] = modbus_update(holdingRegs);
holdingRegs[BUTTON0] = analogRead(buttonPin0);
delayMicroseconds(50);
holdingRegs[BUTTON1] = analogRead(buttonPin1);
delayMicroseconds(50);
}
================================================
FILE: SimpleModbusSlaveSoftwareSerial/keywords.txt
================================================
modbus_configure KEYWORD2
modbus_update KEYWORD2
================================================
FILE: gpl-3.0.txt
================================================
GNU GENERAL PUBLIC LICENSE
Version 3, 29 June 2007
Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
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software and other kinds of works.
The licenses for most software and other practical works are designed
to take away your freedom to share and change the works. By contrast,
the GNU General Public License is intended to guarantee your freedom to
share and change all versions of a program--to make sure it remains free
software for all its users. We, the Free Software Foundation, use the
GNU General Public License for most of our software; it applies also to
any other work released this way by its authors. You can apply it to
your programs, too.
When we speak of free software, we are referring to freedom, not
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To protect your rights, we need to prevent others from denying you
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Developers that use the GNU GPL protect your rights with two steps:
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The precise terms and conditions for copying, distribution and
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gitextract_8ia3zrgx/ ├── .github/ │ └── FUNDING.yml ├── README.md ├── SimpleModbusMaster/ │ ├── SimpleModbusMaster.cpp │ ├── SimpleModbusMaster.h │ ├── examples/ │ │ └── SimpleModbusMasterExample/ │ │ └── SimpleModbusMasterExample.ino │ └── keywords.txt ├── SimpleModbusMasterSoftwareSerial/ │ ├── SimpleModbusMasterSoftwareSerial.cpp │ └── SimpleModbusMasterSoftwareSerial.h ├── SimpleModbusSlave/ │ ├── SimpleModbusSlave.cpp │ ├── SimpleModbusSlave.h │ ├── examples/ │ │ └── SimpleModbusSlaveExample/ │ │ └── SimpleModbusSlaveExample.ino │ └── keywords.txt ├── SimpleModbusSlaveSoftwareSerial/ │ ├── SimpleModbusSlaveSoftwareSerial.cpp │ ├── SimpleModbusSlaveSoftwareSerial.h │ ├── examples/ │ │ └── SimpleModbusTinyExample/ │ │ └── SimpleModbusTinyExample.ino │ └── keywords.txt └── gpl-3.0.txt
SYMBOL INDEX (35 symbols across 6 files)
FILE: SimpleModbusMaster/SimpleModbusMaster.cpp
function modbus_update (line 36) | unsigned int modbus_update(Packet* packets)
function constructPacket (line 88) | void constructPacket()
function checkResponse (line 134) | void checkResponse()
function check_packet_status (line 183) | void check_packet_status()
function check_F3_data (line 230) | void check_F3_data(unsigned char buffer)
function check_F16_data (line 261) | void check_F16_data()
function getData (line 283) | unsigned char getData()
function modbus_configure (line 322) | void modbus_configure(long baud, unsigned int _timeout, unsigned int _po...
function calculateCRC (line 371) | unsigned int calculateCRC(unsigned char bufferSize)
function sendPacket (line 391) | void sendPacket(unsigned char bufferSize)
FILE: SimpleModbusMaster/SimpleModbusMaster.h
type Packet (line 107) | typedef struct {
type Packet (line 138) | typedef Packet* packetPointer;
FILE: SimpleModbusMasterSoftwareSerial/SimpleModbusMasterSoftwareSerial.cpp
function modbus_packet_init (line 37) | void modbus_packet_init(Packet *packet, unsigned char id, unsigned char ...
function modbus_update (line 45) | unsigned int modbus_update(Packet* packets)
function constructPacket (line 88) | void constructPacket()
function checkResponse (line 139) | void checkResponse()
function check_packet_status (line 193) | void check_packet_status()
function check_F3_data (line 246) | void check_F3_data(unsigned char buffer)
function check_F16_data (line 284) | void check_F16_data()
function getData (line 307) | unsigned char getData()
function modbus_configure (line 349) | void modbus_configure(SoftwareSerial* comPort, long baud,
function calculateCRC (line 404) | unsigned int calculateCRC(unsigned char bufferSize)
function sendPacket (line 426) | void sendPacket(unsigned char bufferSize)
FILE: SimpleModbusMasterSoftwareSerial/SimpleModbusMasterSoftwareSerial.h
type Packet (line 108) | typedef struct
type Packet (line 139) | typedef Packet* packetPointer;
FILE: SimpleModbusSlave/SimpleModbusSlave.cpp
function modbus_update (line 22) | unsigned int modbus_update(unsigned int *holdingRegs)
function exceptionResponse (line 148) | void exceptionResponse(unsigned char exception)
function modbus_configure (line 162) | void modbus_configure(long baud, unsigned char _slaveID, unsigned char _...
function calculateCRC (line 203) | unsigned int calculateCRC(byte bufferSize)
function sendPacket (line 223) | void sendPacket(unsigned char bufferSize)
FILE: SimpleModbusSlaveSoftwareSerial/SimpleModbusSlaveSoftwareSerial.cpp
function modbus_update (line 23) | unsigned int modbus_update(unsigned int *holdingRegs)
function exceptionResponse (line 149) | void exceptionResponse(unsigned char exception)
function modbus_configure (line 163) | void modbus_configure(SoftwareSerial* comPort, long baud, unsigned char ...
function calculateCRC (line 197) | unsigned int calculateCRC(byte bufferSize)
function sendPacket (line 217) | void sendPacket(unsigned char bufferSize)
Condensed preview — 17 files, each showing path, character count, and a content snippet. Download the .json file or copy for the full structured content (128K chars).
[
{
"path": ".github/FUNDING.yml",
"chars": 40,
"preview": "custom: https://paypal.me/angelocomp/10\n"
},
{
"path": "README.md",
"chars": 1163,
"preview": "# SimpleModbus NG\n\nSimpleModbus is a collection of Arduino libraries that enables you to communicate serially using the "
},
{
"path": "SimpleModbusMaster/SimpleModbusMaster.cpp",
"chars": 15362,
"preview": "#include \"SimpleModbusMaster.h\"\r\n\r\n#define BUFFER_SIZE 128\r\n\r\n// modbus specific exceptions\r\n#define ILLEGAL_FUNCTION 1\r"
},
{
"path": "SimpleModbusMaster/SimpleModbusMaster.h",
"chars": 6013,
"preview": "#ifndef SIMPLE_MODBUS_MASTER_H\r\n#define SIMPLE_MODBUS_MASTER_H\r\n\r\n/*\r\n SimpleModbusMaster allows you to communicate\r\n "
},
{
"path": "SimpleModbusMaster/examples/SimpleModbusMasterExample/SimpleModbusMasterExample.ino",
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"preview": "#include <SimpleModbusMaster.h>\n\n/* To communicate with a slave you need to create a\n packet that will contain all the"
},
{
"path": "SimpleModbusMaster/keywords.txt",
"chars": 186,
"preview": "Packet\tKEYWORD1\r\npacketPointer\tKEYWORD1\r\nmodbus_configure\tKEYWORD2\r\nmodbus_port\tKEYWORD2\r\n\r\n###### Constants ######\r\nREA"
},
{
"path": "SimpleModbusMasterSoftwareSerial/SimpleModbusMasterSoftwareSerial.cpp",
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"preview": "#include \"SimpleModbusMasterSoftwareSerial.h\"\r\n\r\n#define BUFFER_SIZE 128\r\n\r\n// modbus specific exceptions\r\n#define ILLEG"
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"path": "SimpleModbusMasterSoftwareSerial/SimpleModbusMasterSoftwareSerial.h",
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"preview": "#ifndef SIMPLE_MODBUS_MASTER_H\r\n#define SIMPLE_MODBUS_MASTER_H\r\n\r\n/* \r\n SoftwareSerial has limitations and is NOT SUPP"
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{
"path": "SimpleModbusSlave/SimpleModbusSlave.cpp",
"chars": 10720,
"preview": "#include \"SimpleModbusSlave.h\"\r\n\r\n#define BUFFER_SIZE 128\r\n\r\n// frame[] is used to recieve and transmit packages.\r\n// Th"
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{
"path": "SimpleModbusSlave/SimpleModbusSlave.h",
"chars": 3674,
"preview": "#ifndef SIMPLE_MODBUS_SLAVE_H\r\n#define SIMPLE_MODBUS_SLAVE_H\r\n\r\n/*\r\n SimpleModbusSlave allows you to communicate\r\n to "
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"path": "SimpleModbusSlave/examples/SimpleModbusSlaveExample/SimpleModbusSlaveExample.ino",
"chars": 4397,
"preview": "#include <SimpleModbusSlave.h>\n\n#define ledPin 13 // onboard led \n#define buttonPin 7 // push button\n\n/* This exampl"
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"path": "SimpleModbusSlave/keywords.txt",
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"preview": "modbus_configure KEYWORD2\r\nmodbus_update\t KEYWORD2\r\n"
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"path": "SimpleModbusSlaveSoftwareSerial/SimpleModbusSlaveSoftwareSerial.cpp",
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"preview": "#include \"SimpleModbusSlaveSoftwareSerial.h\"\r\n\r\n#define BUFFER_SIZE 128\r\n\r\n// frame[] is used to recieve and transmit pa"
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"path": "SimpleModbusSlaveSoftwareSerial/SimpleModbusSlaveSoftwareSerial.h",
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"preview": "#ifndef SIMPLE_MODBUS_SLAVE_H\r\n#define SIMPLE_MODBUS_SLAVE_H\r\n\r\n/*\r\n SimpleModbusSlave allows you to communicate\r\n to "
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"path": "SimpleModbusSlaveSoftwareSerial/examples/SimpleModbusTinyExample/SimpleModbusTinyExample.ino",
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"preview": "#include <SoftwareSerial.h>\n#include <SimpleModbusSlaveSoftwareSerial.h>\n\n#define buttonPin0 2 // push button\n#define "
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"path": "SimpleModbusSlaveSoftwareSerial/keywords.txt",
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"preview": "modbus_configure KEYWORD2\r\nmodbus_update\t KEYWORD2\r\n"
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{
"path": "gpl-3.0.txt",
"chars": 35147,
"preview": " GNU GENERAL PUBLIC LICENSE\n Version 3, 29 June 2007\n\n Copyright (C) 2007 Free "
}
]
About this extraction
This page contains the full source code of the angeloc/simplemodbusng GitHub repository, extracted and formatted as plain text for AI agents and large language models (LLMs). The extraction includes 17 files (119.3 KB), approximately 28.2k tokens, and a symbol index with 35 extracted functions, classes, methods, constants, and types. Use this with OpenClaw, Claude, ChatGPT, Cursor, Windsurf, or any other AI tool that accepts text input. You can copy the full output to your clipboard or download it as a .txt file.
Extracted by GitExtract — free GitHub repo to text converter for AI. Built by Nikandr Surkov.