====== Modbus RTU Master SW-Serial-lal ======

A program Arduino UNO-n fut. Az UNO-nak csak egy soros portja van, ezért a sw-serial egy nagyon hasznos funkció, mert több kvázi-UART-tot is nyithatunk vele. Problémája, hogy több kommunikációs megoldással nem működik. Ebben az esetben viszont igen, az Arduino Modbus RTU Masterként működik, miközben a serial monitor is fut rajta. 

===== Vezetékezés =====
{{:hu:arduino:modbus_rtu_over_max485_with_sw_serial_steckplatine.png|Modbus RTU Master SW-Serial}}
===== Könyvtár =====
  * modbusrtu.h: https://github.com/smarmengol/Modbus-Master-Slave-for-Arduino
  * SoftwareSerial.h: https://www.arduino.cc/en/Reference/softwareSerial
==== Program ====
<code c>
// Arduino UNO
// Modbus RTU - Master
// comm over sw serial

#include <ModbusRtu.h>
#include <SoftwareSerial.h>

// data array for modbus network sharing
uint16_t au16data[16];
uint8_t u8state;
#define SSerialTxControl 10
/**
 *  Modbus object declaration
 *  u8id : node id = 0 for master, = 1..247 for slave
 *  u8serno : serial port (use 0 for Serial)
 */

// this is master USB-FTDI via software serial 
Modbus master(0); 
/**
 * This is an structe which contains a query to an slave device
 */
modbus_t telegram;

unsigned long u32wait;

SoftwareSerial mySerial(2, 3);//Create a SoftwareSerial object so that we can use software serial. Search "software serial" on Arduino.cc to find out more details.

void setup() {
  //use the hardware serial if you want to connect to your computer via usb cable 
  Serial.begin(9600);
  // begin the ModBus object. The first parameter is the address of your SoftwareSerial address. 
  // Do not forget the "&". 9600 means baud-rate at 9600
  master.begin( &mySerial, 9600, SSerialTxControl ); 
  // if there is no answer in 2000 ms, roll over
  master.setTimeOut( 2000 ); 
  u32wait = millis() + 1000;
  u8state = 0; 
}

void loop() {
  switch( u8state ) {
  case 0: 
    if (millis() > u32wait) u8state++; // wait state
    break;
  case 1: 
    telegram.u8id = 0x01;         // slave address
    // master functionen: 
    // 03: read holding reg., 06: write holdong reg., 10: write more holding reg.
    telegram.u8fct = 0x03;        // function code
    telegram.u16RegAdd = 0x00;    // start address in slave
    telegram.u16CoilsNo = 0x10;   // number of elements (coils or registers) to read
    telegram.au16reg = au16data;  // pointer to a memory array in the Arduino

    master.query( telegram );     // send query (only once)
    u8state++;
    break;
  case 2:
    master.poll();                // check incoming messages
    if (master.getState() == COM_IDLE) {
      u8state = 0;
      u32wait = millis() + 2000;  // wait for answer
        // print it to serial monitor 
        Serial.print("Register 0x00 :");
        Serial.println(au16data[0]); 
        Serial.print("Register 0x01 :");
        Serial.println(au16data[1]); 
        Serial.print("Register 0x02 :");
        Serial.println(au16data[2]); 
        Serial.print("Register 0x03 :");
        Serial.println(au16data[3]); 
        Serial.print("Register 0x04 :");
        Serial.println(au16data[4]); 
        Serial.print("Register 0x05 :");
        Serial.println(au16data[5]); 
        Serial.print("Register 0x06 :");
        Serial.println(au16data[6]); 
        Serial.print("Register 0x07 :");
        Serial.println(au16data[7]); 
        Serial.print("Register 0x08 :");
        Serial.println(au16data[8]); 
        Serial.print("Register 0x09 :");
        Serial.println(au16data[9]); 
        
    }
    break;
  }
}
</code>

{{:de:arduino:com3335625.png|log}}