README.md

Simple Modbus Slave

Introduction

Arduino Simple Modbus Slave is an ISC licensed library to handle Modbus requests on Arduino (slave).

Features

To keep it simple and to reduce memory consumption, only the two following Modbus functions are supported:

• read holding registers (0x03)
• write multiple registers (0x10)

Example

#include <SimpleModbusSlave.h>

SimpleModbusSlave slave(1);   // Initialize the slave with the ID 1
uint16_t regs[10];            // Allocate a mapping of 10 values

void setup() {
    // Initialize the first register to have a value to read
    regs[0] = 0x1234;

    // The transfer speed is set to 115200 bauds
    slave.setup(115200);
}

void loop() {
    // Launch Modbus slave loop with:
    // - pointer to the mapping
    // - max values of mapping
    slave.loop(regs, sizeof(regs) / sizeof(regs[0]));
}

Contribute

I want to keep this library very basic and small so if you want to contribute:

1. Check for open issues or open a fresh issue to start a discussion around a feature idea or a bug.
2. Fork the repository on Github to start making your changes on another branch.
3. Send a pull request (of your small and atomic changes).
4. Bug the maintainer if he's too busy to answer :)