Hilfe bezüglich Modbus

/**

    Modbus master example 1:

    The purpose of this example is to query an array of data

    from an external Modbus slave device.

    The link media can be USB or RS232.

    Recommended Modbus slave:

    diagslave http://www.modbusdriver.com/diagslave.html

    In a Linux box, run

    "./diagslave /dev/ttyUSB0 -b 19200 -d 8 -s 1 -p none -m rtu -a 1"

    This is:

      serial port /dev/ttyUSB0 at 19200 baud 8N1

     RTU mode and address @1

*/

#include <ModbusRtu.h>

// data array for modbus network sharing

uint16_t au16data[16];

uint8_t u8state;

/**

    Modbus object declaration

    u8id : node id = 0 for master, = 1..247 for slave

    port : serial port

    u8txenpin : 0 for RS-232 and USB-FTDI

                 or any pin number > 1 for RS-485

*/

Modbus master(0, Serial, 2); // this is master and RS-232 or USB-FTDI

/**

   This is an structe which contains a query to an slave device

*/

modbus_t telegram;

unsigned long u32wait;

void setup() {

  Serial.begin( 9600 ); // baud-rate at 9600

  Serial.println("start");

  master.start();

  master.setTimeOut( 1000 ); // if there is no answer in 2000 ms, roll over

  u32wait = millis() + 1000;

  u8state = 0;

}

void loop() {

  switch ( u8state ) {

    case 0:

      if (millis() > u32wait) u8state++; // wait state

      break;

    case 1:

      telegram.u8id = 240; // slave address

      telegram.u8fct = 4; // function code (this one is registers read)

      telegram.u16RegAdd = 30061; // start address in slave

      telegram.u16CoilsNo = 7; // 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() + 100;

      }

      break;

  }

}