Slave to master write problem

Hi Chris,

I have been working on simple modbus communication but, I haven't succeeded yet. I need your help.

I want to write boolean value from slave and read it from master. I have two Arduino nano and two TTL rs485 converter.

Both Arduino pin connection; R0 to RX(D0) DI to TX(D1) DE and RE to D2 A to A B to B

Where is problem? Could you help me?

Slave code

#include "NewPing.h"
#include <ModbusRTUSlave.h>

#define TRIGGER_PIN 9
#define ECHO_PIN 10
#define MAX_DISTANCE 400
#define TRESHOLD_DISTINCE 30 //100

NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE);
float duration, distance;

#define SERIAL_BAUD 38400
#define SERIAL_CONFIG SERIAL_8N1
#define SLAVE_ID 1 
#define TXEN    2

ModbusRTUSlave slave(Serial, TXEN);
bool discreteInputs[1];
bool oldStatus = false;
bool newStatus = false;

void setup() {
  discreteInputs[0] = false;
  Serial.begin( SERIAL_BAUD, SERIAL_8E1 ); // 19200 baud, 8-bits, even, 1-bit stop
  slave.configureCoils(discreteInputs, 1);
  slave.begin(SLAVE_ID, SERIAL_BAUD, SERIAL_8E1);
}

void loop() {

  distance = sonar.ping_cm();

  Serial.print("DIST ");
  // Send results to Serial Monitor
  distance = distance == 0? 400 : distance;
  if (distance >= 400 || distance <= 2) {
    Serial.print("- |");
  } else {
    Serial.print(distance);
    Serial.print(" | ");
  }

  if (distance < TRESHOLD_DISTINCE) {
    Serial.print(" PARK F | ");
    newStatus = true;
  } else {
    Serial.print(" PARK E | ");
    newStatus = false;
  }

  if (oldStatus != newStatus) {
    oldStatus = newStatus;
    discreteInputs[0] = newStatus;
  }

  slave.poll();

  Serial.println();
  delay(1000);
}

Master code

#include <ModbusRTUMaster.h>

#define SERIAL_BAUD 38400
#define SERIAL_CONFIG SERIAL_8N1
#define TXEN    2

ModbusRTUMaster modbus(Serial, TXEN);
bool discreteInputs[1];

void setup() {
  Serial.begin(SERIAL_BAUD);
  modbus.begin(SERIAL_BAUD);
}

void loop() { 
  modbus.readCoils(1, 0, discreteInputs, 1);
  uint8_t reesponse = modbus.getExceptionResponse();
  Serial.print( reesponse );
  Serial.print(" |");
  Serial.print(discreteInputs[0]);
  Serial.print(" |");
  Serial.println();
  delay(1000);
}

Best regards, Seref

CMB27 / ModbusRTUSlave

Slave to master write problem #37