Arduino Modbus Master code to read data using arduino uno from EB meter

Question

I am using DC energy meter as slave.When I am testing DC energy meter using Modbus tester tool,its showing value from 1 to 24 register.I am using my own atmega328P with on board RS485 as a master device.I have connected A,B from slave to mater board.Now,I want to read slave outputs using my master.For that I have written below mentioned code.when I am serially printing array,its showing 00000000000000000000000000000000769.I am not getting full data on my master.

#include <ModbusRtu.h>

// data array for modbus network sharing
uint16_t au16data[64];
uint8_t u8state;

int i;

/**
 *  Modbus object declaration
 *  u8id : node id = 0 for master, = 1..247 for slave
 *  u8serno : serial port (use 0 for Serial)
 *  u8txenpin : 0 for RS-232 and USB-FTDI 
 *               or any pin number > 1 for RS-485
 */
Modbus master(0,0,1); // 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() {
  master.begin( 9600 ); // baud-rate at 19200
  master.setTimeOut( 2000 ); // 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 = 1; // slave address
    telegram.u8fct = 3; // function code (this one is registers read)
    telegram.u16RegAdd = 1; // start address in slave
    telegram.u16CoilsNo = 24; // 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;
  }
 //au16data[4] = analogRead( 0 );

 for(i=0;i<=64;i++)
 {
  Serial.print(au16data[i]);
 }
 Serial.println("\n");
 Serial.println("\n");
 delay(1000);
 }

Answer 1

The response is received when ModbusRtu library object is again in the IDLE state after a request was sent. In your code based on the example from the library, the response is ready in state 2 which follows state 1 where the request was sent. If in state 2 when the master object state changes to IDLE, you can use the response in array au16data.