Example Code for Arduino-Read Dissolved Oxygen, Saturation, and Temperature

Hardware Preparation

• DFRduino UNO R3 (or similar) x 1
• Gravity: Active Isolated RS485 to UART Signal Adapter Module x1
• RS485 Dissolved Oxygen Sensor x1

Software Preparation

• Arduino IDE

Wiring Diagram

If the power of the RS485 device is small and the required current is less than 12V-160mA, the RS485 to UART signal conversion module does not require a 12V external power supply, making wiring more convenient.

Other Preparation Work

No additional preparation work is required beyond the hardware and software setup and wiring.

Sample Code

#include <SoftwareSerial.h>
SoftwareSerial mySerial(2, 3);                                         //TX,RX
uint8_t Com[8] = { 0x01, 0x03, 0x00, 0x00, 0x00, 0x06, 0xC5, 0xC8 };   
uint8_t Com1[8] = { 0x01, 0x03, 0x10, 0x22, 0x00, 0x01, 0x20, 0xC0 };  
uint8_t Com2[8] = { 0x01, 0x03, 0x10, 0x20, 0x00, 0x01, 0x81, 0x00 };  
float sal, ap;

void setup() {
  Serial.begin(9600);
  mySerial.begin(4800);
}
void loop() {
  readDO_DOS_TEM();
  Atmospheric_pressure();
  Serial.print("AP = ");
  Serial.print(ap, 2);
  Serial.print("Kpa  ");
  Salinity();
  Serial.print("Salinityt = ");
  Serial.print(sal,0);
  Serial.println("%  ");
  Serial.println("   ");
  delay(1000);
}

void readDO_DOS_TEM(void) {
  uint32_t val = 0, val1 = 0, val2 = 0;
  uint8_t Data[18] = { 0 };
  uint8_t ch = 0;
  bool flag = 1;
  long timeStart = millis();
  long timeStart1 = 0;
  while (flag) {

    if ((millis() - timeStart1) > 100) {
      while (mySerial.available() > 0) {
        mySerial.read();
      }
      mySerial.write(Com, 8);
      timeStart1 = millis();
    }

    if ((millis() - timeStart) > 1000) {
      Serial.println("Time out");
      return -1;
    }

    if (readN(&ch, 1) == 1) {
      if (ch == 0x01) {
        Data[0] = ch;
        if (readN(&ch, 1) == 1) {
          if (ch == 0x03) {
            Data[1] = ch;
            if (readN(&ch, 1) == 1) {
              if (ch == 0x0C) {
                Data[2] = ch;
                if (readN(&Data[3], 14) == 14) {
                  if (CRC16_2(Data, 15) == (Data[15] * 256 + Data[16])) {
                    val = Data[3];
                    val = (val << 8) | Data[4];
                    val = (val << 8) | Data[5];
                    val = (val << 8) | Data[6];
                    float *dos = (float *)&val;
                    float Dos = *dos * 100.00;
                    Serial.print("DO Sat = ");
                    Serial.print(Dos, 1);
                    Serial.print("%  ");
                    val1 = Data[7];
                    val1 = (val1 << 8) | Data[8];
                    val1 = (val1 << 8) | Data[9];
                    val1 = (val1 << 8) | Data[10];
                    float *Do = (float *)&val1;
                    Serial.print("DO = ");
                    Serial.print(*Do, 2);
                    Serial.print(" mg/L  ");
                    val2 = Data[11];
                    val2 = (val2 << 8) | Data[12];
                    val2 = (val2 << 8) | Data[13];
                    val2 = (val2 << 8) | Data[14];
                    float *tem = (float *)&val2;
                    Serial.print("TEM = ");
                    Serial.print(*tem, 1);
                    Serial.println("°C");
                    flag = 0;
                  }
                }
              }
            }
          }
        }
      }
    }
  }
}

void Atmospheric_pressure(void) {
  uint8_t Data[12] = { 0 };
  uint8_t ch = 0;
  bool flag = 1;
  long timeStart = millis();
  long timeStart1 = 0;
  while (flag) {

    if ((millis() - timeStart1) > 100) {
      while (mySerial.available() > 0) {
        mySerial.read();
      }
      mySerial.write(Com1, 8);
      timeStart1 = millis();
    }

    if ((millis() - timeStart) > 1000) {
      Serial.println("Time out2");
      return -1;
    }

    if (readN(&ch, 1) == 1) {
      if (ch == 0x01) {
        Data[0] = ch;
        if (readN(&ch, 1) == 1) {
          if (ch == 0x03) {
            Data[1] = ch;
            if (readN(&ch, 1) == 1) {
              if (ch == 0x02) {
                Data[2] = ch;
                if (readN(&Data[3], 4) == 4) {
                  if (CRC16_2(Data, 5) == (Data[5] * 256 + Data[6])) {
                    ap = (Data[3] * 256 + Data[4]) / 100.0;
                    flag = 0;
                  }
                }
              }
            }
          }
        }
      }
    }
  }
}

void Salinity(void) {
  uint8_t Data[12] = { 0 };
  uint8_t ch = 0;
  bool flag = 1;
  long timeStart = millis();
  long timeStart1 = 0;
  while (flag) {

    if ((millis() - timeStart1) > 100) {
      while (mySerial.available() > 0) {
        mySerial.read();
      }
      mySerial.write(Com2, 8);
      timeStart1 = millis();
    }

    if ((millis() - timeStart) > 1000) {
      Serial.println("Time out3");
      return -1;
    }

    if (readN(&ch, 1) == 1) {
      if (ch == 0x01) {
        Data[0] = ch;
        if (readN(&ch, 1) == 1) {
          if (ch == 0x03) {
            Data[1] = ch;
            if (readN(&ch, 1) == 1) {
              if (ch == 0x02) {
                Data[2] = ch;
                if (readN(&Data[3], 4) == 4) {
                  if (CRC16_2(Data, 5) == (Data[5] * 256 + Data[6])) {
                    sal = Data[3] * 256 + Data[4];
                    flag = 0;
                  }
                }
              }
            }
          }
        }
      }
    }
  }
}

uint8_t readN(uint8_t *buf, size_t len) {
  size_t offset = 0, left = len;
  int16_t Tineout = 500;
  uint8_t *buffer = buf;
  long curr = millis();
  while (left) {
    if (mySerial.available()) {
      buffer[offset] = mySerial.read();
      offset++;
      left--;
    }
    if (millis() - curr > Tineout) {
      break;
    }
  }
  return offset;
}

unsigned int CRC16_2(unsigned char *buf, int len) {
  unsigned int crc = 0xFFFF;
  for (int pos = 0; pos < len; pos++) {
    crc ^= (unsigned int)buf[pos];
    for (int i = 8; i != 0; i--) {
      if ((crc & 0x0001) != 0) {
        crc >>= 1;
        crc ^= 0xA001;
      } else {
        crc >>= 1;
      }
    }
  }

  crc = ((crc & 0x00ff) << 8) | ((crc & 0xff00) >> 8);
  return crc;
}

Result

The serial port prints the dissolved oxygen concentration, dissolved oxygen saturation, temperature, atmospheric pressure, and salinity values ​​collected by the sensor.