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140 lines
6.2 KiB
140 lines
6.2 KiB
# Modbus Serial Library for Arduino
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Over Serial Line Implementation RTU (OSI 2/OSI 1)
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[](https://github.com/epsilonrt/modbus-serial/releases)
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[](https://registry.platformio.org/libraries/epsilonrt/modbus-serial)
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[](https://www.arduinolibraries.info/libraries/modbus-serial)
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[](https://www.arduino.cc/)
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[](https://github.com/epsilonrt/modbus-serial/actions/workflows/build_uno.yml)
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[](https://github.com/epsilonrt/modbus-serial/actions/workflows/build_due.yml)
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[](https://github.com/epsilonrt/modbus-serial/actions/workflows/build_mega.yml)
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[](https://github.com/epsilonrt/modbus-serial/actions/workflows/build_nano33iot.yml)
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[](https://github.com/epsilonrt/modbus-serial/actions/workflows/build_teensy.yml)
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[](https://github.com/epsilonrt/modbus-serial/actions/workflows/build_esp8266.yml)
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[](https://github.com/epsilonrt/modbus-serial/actions/workflows/build_esp32.yml)
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---
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This library allows your Arduino to communicate via Modbus protocol. The Modbus is a master-slave protocol
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used in industrial automation and can be used in other areas, such as home automation.
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In the current version the library allows the Arduino operate **as a slave**, supporting Modbus over Serial Line RTU.
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## How to
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There are four classes corresponding to five headers that may be used:
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* [Modbus-Arduino](http://github.com/epsilonrt/modbus-arduino ) - Base Library
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* Modbus-Serial - Modbus Serial RTU Library (this repository)
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* [Modbus-Ethernet](https://github.com/epsilonrt/modbus-ethernet) - Modbus TCP Library (standard Ethernet Shield)
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* [Modbus-EtherCard](https://github.com/epsilonrt/modbus-ethercard) - Modbus TCP Library (for ENC28J60 chip)
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* [Modbus-Esp8266AT](https://github.com/epsilonrt/modbus-esp8266at) - Modbus IP Library (for ESP8266 chip with AT firmware)
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By opting for Modbus Serial or Modbus TCP you must include in your sketch the corresponding header, eg:
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#include <ModbusSerial.h>
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## Modbus-Serial
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There are five examples that can be accessed from the Arduino IDE or Visual
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Studio Code with Platformio, once you have installed the library.
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Let's look at the example Lamp.ino (only the parts concerning Modbus will be commented):
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#include <ModbusSerial.h>
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Inclusion of the necessary header.
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const int Lamp1Coil = 0;
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Sets the Modbus register to represent a lamp or LED. This value is the offset (0-based) to be placed in its supervisory or testing software.
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Note that if your software uses offsets 1-based the set value there should be 1, for this example.
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ModbusSerial mb (Serial, SlaveId);
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Create the mb instance (ModbusSerial) to be used with the serial port `Serial`.
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Note that the serial port is passed as reference, which permits the use of other
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serial ports in other Arduino models, also ets the slave Id.
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If you are using RS-485 driver, the configuration of another pin to control
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transmission/reception is required, this pin would be connected to the DE and
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/RE pins of the driver. This is done as follows:
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const int TxenPin = 4;
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// ....
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ModbusSerial mb (Serial, SlaveId, TxenPin);
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In this case, the pin 4 will be used to control TX/RX (DE must be connected with /RE).
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Serial.begin (Baudrate, MB_PARITY_EVEN);
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while (! Serial)
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;
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Configure the serial port and wait for it to be ready.
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To simplify the modification of the port, you can define a macro in the following way :
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#define MySerial Serial // define serial port used, Serial most of the time, or Serial1, Serial2 ... if available
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Then the block above can be written as follows :
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ModbusSerial mb (MySerial, SlaveId, TxenPin);
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void setup() {
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MySerial.begin (Baudrate, MB_PARITY_EVEN); // prefer this line in accordance with the modbus standard.
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while (! MySerial)
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;
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mb.config (Baudrate);
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The last line configures the ModbusSerial object.
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mb.addCoil (Lamp1Coil);
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Adds the register type Coil (digital output) that will be responsible for
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activating the LED or lamp and verify their status.
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The library allows you to set an initial value for the register:
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mb.addCoil (Lamp1Coil, true);
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In this case the register is added and set to true. If you use the first form
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the default value is false.
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mb.task ();
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This method makes all magic, answering requests and changing the registers if
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necessary, it should be called only once, early in the loop.
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digitalWrite (LedPin, mb.coil (Lamp1Coil));
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Finally the value of Lamp1Coil register is used to drive the lamp or LED.
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In much the same way, the other examples show the use of other methods available in the library:
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void addCoil (offset word, bool value)
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void addHreg (offset word, word value)
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void addIsts (offset word, bool value)
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void addIreg (offset word, word value)
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Adds registers and configures initial value if specified.
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bool setCoil (offset word, bool value)
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bool setHreg (offset word, word value)
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bool setIsts (offset word, bool value)
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bool setIReg (offset word, word value)
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Sets a value to the register.
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bool coil (offset word)
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word hreg (word offset)
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bool ists (offset word)
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word ireg (word offset)
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Returns the value of a register.
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License
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=======
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The code in this repo is licensed under the BSD New License. See LICENSE for more info.
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