IO Expansion Shield For Arduino (V5) (SKU: DFR0088). RS485 интерфейс.

#include "ModbusMaster.h"

/*!
  IO Expansion Shield For Arduino (V5) (SKU: DFR0088) RS485 interface.

  We're using a MAX485-compatible RS485 Transceiver.
  Rx/Tx is hooked up to the hardware serial port at 'Serial'.
  The Data Enable (DE) and Receiver Enable (RE) pins are hooked up as follows:
*/
#define MAX485_RE_NEG  2 //RS485 has a enable/disable pin to transmit or receive data. Arduino Digital Pin 2 = Rx/Tx 'Enable'; High to Transmit, Low to Receive
#define Slave_ID       1 

// instantiate ModbusMaster object
ModbusMaster node;

void preTransmission()
{
  digitalWrite(MAX485_RE_NEG, HIGH); //Switch to transmit data
}

void postTransmission()
{
  digitalWrite(MAX485_RE_NEG, LOW); //Switch to receive data
}

void setup()
{
  pinMode(MAX485_RE_NEG, OUTPUT);

  // Init in receive mode
  digitalWrite(MAX485_RE_NEG, LOW);

  // Modbus communication runs at 9600 baud
  Serial.begin(9600, SERIAL_8N1);

  // Modbus slave ID 1
  node.begin(Slave_ID, Serial);

  // Callbacks allow us to configure the RS485 transceiver correctly
  node.preTransmission(preTransmission);
  node.postTransmission(postTransmission);
}

void loop()
{
  // Read 2 registers starting at 0x01
  uint8_t result = node.readInputRegisters(0x01, 2);
  if (getResultMsg(result))
  {
    Serial.println();
    
    double res_dbl = node.getResponseBuffer(0)/10;
    String res = "Temperature: " + String(res_dbl) + " C\r\n";
    res_dbl = node.getResponseBuffer(1)/10;
    res += "Humidity: " + String(res_dbl) + " %";
    Serial.println(res);
 }
 delay(10000);
}

bool getResultMsg(uint8_t result)
{
  String tmpstr2;

  switch (result) {
  case node.ku8MBSuccess:
    return true;
    break;
  case node.ku8MBIllegalFunction:
    tmpstr2 = "Illegal Function";
    break;
  case node.ku8MBIllegalDataAddress:
    tmpstr2 = "Illegal Data Address";
    break;
  case node.ku8MBIllegalDataValue:
    tmpstr2 = "Illegal Data Value";
    break;
  case node.ku8MBSlaveDeviceFailure:
    tmpstr2 = "Slave Device Failure";
    break;
  case node.ku8MBInvalidSlaveID:
    tmpstr2 = "Invalid Slave ID";
    break;
  case node.ku8MBInvalidFunction:
    tmpstr2 = "Invalid Function";
    break;
  case node.ku8MBResponseTimedOut:
    tmpstr2 = "Response Timed Out";
    break;
  case node.ku8MBInvalidCRC:
    tmpstr2 = "Invalid CRC";
    break;
  default:
    tmpstr2 = "Unknown error: " + String(result);
    break;
  }
  Serial.println(tmpstr2);
  return false;
}