XY_MD02_SP3485.cpp

#include <ModbusMaster.h>

#define RS485_RX_PIN (15)
#define RS485_TX_PIN (17)
#define RS485_DIR_PIN (16)

ModbusMaster sensor;

void preTransmission() {
  digitalWrite(RS485_DIR_PIN, HIGH);
}

void postTransmission() {
  digitalWrite(RS485_DIR_PIN, LOW);
}

void setup() {
  Serial.begin(115200);

  pinMode(RS485_DIR_PIN, OUTPUT);
  digitalWrite(RS485_DIR_PIN, LOW);
  
  // Modbus communication runs at 9600 baud
  Serial2.begin(9600, SERIAL_8N1, RS485_RX_PIN, RS485_TX_PIN); // AdapBit

  // XY-MD02 init with Modbus slave ID 1
  sensor.begin(1, Serial2);
  sensor.preTransmission(preTransmission);
  sensor.postTransmission(postTransmission);
}

void loop() {
  // XY-MD02 read
  uint8_t result;
  result = sensor.readInputRegisters(1, 2); // Read Input Register start at 1 -> 2 word (0x0001 - 0x0002)
  if (result == sensor.ku8MBSuccess) {\
    float temp_c = sensor.getResponseBuffer(0) / 10.0;
    float humi_rh = sensor.getResponseBuffer(1) / 10.0;

    Serial.println("Temp: " + String(temp_c, 1) + " *C\tHumi: " + String(humi_rh, 1) + " %RH");

    delay(100);
  } else {
    Serial.println("Read XY-MD02 error, check your serial configs, wiring and power supply");
    delay(1000);
  }
}