RS 485 OPTA Library transmitting but not receiving

Hardware Opta
1

Good morning, I have an OPTA with RS485 and need to use the bus to communicate with an instrument.
The communication protocol is not Modbus. Data transmission is successful, but I am encountering issues with receiving data from the device.
Using the same commands with an Arduino Zero and a 485 converter works perfectly. What am I doing wrong?
I keep receiving "�" instead of the correct response.

#include <ArduinoRS485.h> 
constexpr auto baudrate{ 9600 };

// Calculate preDelay and postDelay in microseconds for stable RS-485 transmission
constexpr auto bitduration{ 1.f / baudrate };
constexpr auto wordlen{ 9.6f };  // OR 10.0f depending on the channel configuration
constexpr auto preDelayBR{ bitduration * wordlen * 3.5f * 1e6 };
constexpr auto postDelayBR{ bitduration * wordlen * 3.5f * 1e6 };


void setup() {
  Serial.begin(9600); 
  RS485.begin(9600); 
}

void loop() {

    //Scrive su 485 i dati letti dalla COM Opta 
    if (Serial.available() > 0) {
    String datiRicevuti = Serial.readStringUntil('\r');
    String datiSpediti=(datiRicevuti + '\r');
    writeRS485(datiSpediti);
    }

    //Legge su 485 i dati letti dalla COM Slave
    char* receivedData = readRS485();
      if (receivedData != NULL) {
        String str = String(receivedData);         
        Serial.println("- Receiving: "+str);        
    } 

}


void writeRS485(String command) {
      command += '\r';                             
      RS485.noReceive();
      RS485.beginTransmission();
      delay(10);
      Serial.println("- Sending: "+command);
      RS485.print(command);
      RS485.endTransmission();
     
}

char* readRS485() {
  RS485.endTransmission();
  RS485.receive();
  delay(10);                          
  static char data[100]="";           
  static int index = 0;               
  while (RS485.available() > 0) {     
    char received = RS485.read();     
    if (received == '\r') {           
      data[index] = '\0';             
      index = 0;                      
      return data;                    
    } else {
      if (index < sizeof(data) - 1) { 
        data[index] = received;      
        index++;                      
      }
    }
  }
  return NULL;                        
  RS485.noReceive();
}
2

Try put in setup

void setup() {
  Serial.begin(baudrate); 
  while (!Serial);

  RS485.begin(baudrate);
  RS485.setDelays(preDelayBR, postDelayBR);
}
3

Hi @eric1 ,

Please have a look at the following tutorial:

You can also check:

Best,