test_vacuum.ino

/****************************************************************************
* Author : Victor Dubois
* Test program for reading data from a XGZP6897D differential pressure sensor
* Adapted for the datasheet's C51 example
****************************************************************************/

#include <Wire.h> 

/*
pressure_range (kPa)   K value
131<P≤260               32
65<P≤131                64
32<P≤65                 128
16<P≤32                 256
8<P≤16                  512
4<P≤8                   1024
2≤P≤4                   2048
1≤P<2                   4096
P<1                     8192
*/

#define K 512 // @TODO see table above to choose the correct value for your application
#define I2C_address 0x6D // Unfortunately, it does not seem possible to change it. To use multiple sensors, use the analog version (XGZP6897A)


double readPressure()
{
    unsigned char pressure_H, pressure_M, pressure_L, temperature_H, temperature_L;
    //temporary variables of pressure and temperature
    long int pressure_adc, temperature_adc;
    //The value of pressure and temperature converted by the sensor’s ADC
    double pressure, temperature;
    //The calibrated value of pressure 

    write_one_byte(I2C_address, 0x30, 0x0A);

        
    //indicate a combined conversion (once temperature conversion immediately followed by once sensor signal conversion)
    //more measurement method, check Register 0x30
    
    long timeout = 0;
    while ((Read_One_Byte(I2C_address, 0x30) & 0x08) > 0)// && timeout < 65000)
    {
      timeout++;
      if (timeout > 5000)
      {
        Serial.println("Timeout! Please check the connections");
        break;
      }
    }
    //Judge whether Data collection is over
    delay(20);
    
    pressure_H = Read_One_Byte(I2C_address, 0x06);
    pressure_M = Read_One_Byte(I2C_address, 0x07);
    pressure_L = Read_One_Byte(I2C_address, 0x08);
    
    // Read ADC output Data of Pressure
    pressure_adc = pressure_H * 65536 + pressure_M * 256 + pressure_L;
    //Compute the value of pressure converted by ADC
    if (pressure_adc > 8388608)
    {
      pressure = (pressure_adc - 16777216) / K; //unit is Pa, select appropriate K value according to pressure range. 
    }
    else
    {
      pressure = pressure_adc / K; //unit is Pa, select appropriate K value according to pressure range. //The conversion formula of calibrated pressure, its unit is Pa
    }

    // Debug, feel free to comment this out
    Serial.print("Pressure: ");
    Serial.print(int(pressure));
    Serial.print(", Temperature: ");
    Serial.println(int(temperature));
    
    temperature_H = Read_One_Byte(I2C_address, 0x09);
    temperature_L = Read_One_Byte(I2C_address, 0x0A);
    //Read ADC output data of temperature
    temperature_adc = temperature_H * 256 + temperature_L;
    //Compute the value of temperature converted by ADC
    temperature = (temperature_adc - 65536)/256; // is deg C
    //else // I do not understand this else without an "if" in the documentation
    temperature = temperature_adc / 256; //unit is ℃
    
    //The conversion formula of calibrated temperature, its unit is Centigrade
    
    return pressure;
}

//----write One Byte of Data,Data from Arduino to the sensor----
// Write "thedata" to the sensor's address of "addr"
void write_one_byte(uint8_t device_address, uint8_t addr, uint8_t thedata)
{
  Wire.beginTransmission(device_address);
  Wire.write(addr);
  Wire.write(thedata);
  Wire.endTransmission();
}

//----Read One Byte of Data,Data from the sensor to the Arduino ---- 
uint8_t Read_One_Byte(uint8_t device_address, uint8_t addr)
{
  uint8_t nb_bytes = 1;
  Wire.beginTransmission(device_address);
  Wire.write(addr);
  Wire.endTransmission();
  Wire.requestFrom(device_address, nb_bytes); 
  return Wire.read();    // Receive a byte as character    
}

void setup() {
    Serial.begin(57600);
    Wire.begin();
    Wire.setClock(100000);

    delay(100);

    Serial.println("start");
}

void loop()
{
  double pressure = readPressure();

  Serial.println(pressure);

  delay(100);
}