RS485 not working on Opta - Connection Timed Out Error

Hardware Opta
1

mpoll
mpoll1538×884 193 KB

I am trying to use my Arduino opta for measuring energy meter readings using RS485. I can scan them using modbus poll but when using arduino opta, I always get connection timed out error. I am using the structure followed on the guides on OPTA for energy meter readings. I have also attached modbus poll and energy meter modbus register map. I have used node, Modbus Master but still getting same issue. No parity and 1 bit.

#include "stm32h7xx_ll_gpio.h"

#include <ArduinoModbus.h>
#include <ArduinoRS485.h>

constexpr auto baudrate { 9600 };

constexpr auto bitduration { 1.f / baudrate };
constexpr auto preDelayBR { bitduration * 9.6f * 3.5f * 1e6 };
constexpr auto postDelayBR { bitduration * 9.6f * 3.5f * 1e6 };

#define F7M24 0x01

uint8_t readInputRegisterValues(int dev_address, uint8_t reg_address, int byte_count){
  uint8_t packet;
  if (!ModbusRTUClient.requestFrom(dev_address, INPUT_REGISTERS, reg_address, byte_count)) {
    Serial.print("failed! ");
    Serial.println(ModbusRTUClient.lastError());
    return 0;
  } else {
    Serial.println("success");

    while (ModbusRTUClient.available()) {
        packet = ModbusRTUClient.read();
        Serial.println(packet);
    }
    return packet;
  }
}

void modbus_com_actual(){
  // Actual Measurements
  // Voltage (V)
  V_actual = readInputRegisterValues(F7M24, 1, 2);

  delay(100);
}
void setup(){

 Serial.println("Energy Management - Modbus RTU Client");

  RS485.setDelays(preDelayBR, postDelayBR);

  // start the Modbus RTU client
  // 7M.24 Energy meter specifies 19200 of default baudrate and 8N2 frame
  if (!ModbusRTUClient.begin(baudrate, SERIAL_8N1)) {
    Serial.println("Failed to start Modbus RTU Client!");
    while (1)
        ;
  }

}

void loop(){

modbus_com_actual();

}

77d468606ec32db2211614467242ca28_OP MFM376 Series OP506-V03 12-08-19.pdf (531.2 KB)

2

Did you solve this? I ran into the same issue although I had it working before

3

Yep, I resolved the issue. You have to connect the opposite terminals of the energy meter with Opta's RS485 terminals.
Suppose you had connected A->+ and B->- just connect A with - and B with +.

4

Hello,

Please take a look at the RS-485 section of the Arduino Opta User Manual here https://docs.arduino.cc/tutorials/opta/user-manual#rs-485

Best,