Hi,

I'm trying to connect a modbus-device to my ESP32 10 io relay module, but cannot get it to work.

I have connected an EM340 energy meeter, and have verified the modbus communication with one of my other arduino PLCS (controllino)

I think I have tried everyting, including

* Used external power

* Swapped A/B lines

The behaviour is that I simply get no answer. My code attached below. What have I missed? There arent any jumpers that needs to be configured for rs485 right? Any suggestions?

Output from skecth below is:sending
sending
sending
sending
sending
sending
sending
sending
etc....

#include <ModbusRTUMaster.h>

#include <RS485.h>
ModbusRTUMaster master(RS485);

uint32_t lastSentTime = 0UL;
const uint32_t baudrate = 9600UL;

////////////////////////////////////////////////////////////////////////////////////////////////////
void setup() {
  Serial.begin(9600UL);

  // Start the serial port

  RS485.begin(baudrate, HALFDUPLEX, SERIAL_8N1);
  RS485.setTimeout(1000);


  master.begin(baudrate);
}

////////////////////////////////////////////////////////////////////////////////////////////////////
void loop() {
 

  // Check available responses often
  if (master.isWaitingResponse()) {
    ModbusResponse response = master.available();
    if (response) {
      if (response.hasError()) {
        
        Serial.print("Error ");
        Serial.println(response.getErrorCode());
      } else {       
          Serial.print("Holding Register values: ");
          for (int i = 0; i < 1; ++i) {
            Serial.print(response.getRegister(i));
            Serial.print(',');
        
          Serial.println();
        }
      }
    }
  }
  else {
    // Send a request every 1000ms
    if (millis() - lastSentTime > 1000) {
      Serial.println("sending");
   
      if (!master.readHoldingRegisters(1, 0, 1)) {
 
        Serial.println("Could not send");
      }
 
      lastSentTime = millis();
    }  
  }
}