XY-MD02_IOXESP32-Modbus-shield-Read.ino

float temp = 0, humi = 0;

void readXY_MD02() {
  uint8_t buff[] = {
    0x01, // Devices Address
    0x04, // Function code
    0x00, // Start Address HIGH
    0x01, // Start Address LOW
    0x00, // Quantity HIGH
    0x02, // Quantity LOW
    0x20, // CRC LOW
    0x0B  // CRC HIGH
  };

  Serial2.write(buff, sizeof(buff));
  Serial2.flush(); // wait MODE_SEND completed

  if (Serial2.find("\x01\x04")) {
    delay(50);
    uint8_t n = Serial2.read();
    if (n != 4) {
      Serial.println("Error data size");
      return;
    }

    temp = ((uint16_t)(Serial2.read() << 8) | Serial2.read()) / 10.0;
    humi = ((uint16_t)(Serial2.read() << 8) | Serial2.read()) / 10.0;
  } else {
    Serial.println("ERROR Timeout");
    return;
  }
}

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

  Serial2.begin(9600, SERIAL_8N1, 27, 26); // Rx, Tx
  Serial2.setTimeout(200);
}

void loop() {
  readXY_MD02();
  Serial.print("Temperature: ");
  Serial.print(temp);
  Serial.println(" *C");
  Serial.print("Humidity: ");
  Serial.print(humi);
  Serial.println(" *C");
  delay(500);
}