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daz/depth_sensor.ino

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Created July 27, 2018 12:26
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  1. @hephaestus9 hephaestus9 created this gist Feb 15, 2015.
    182 changes: 182 additions & 0 deletions depth_sensor.ino
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,182 @@

    /*
    MS5541 Pressure Sensor calwords readout
    This program will read your MS5441 or compatible pressure sensor every 5 seconds and show you the calibration words, the calibration factors,
    the raw values and the compensated values of temperature and pressure.
    Once you read out the calibration factors you can define them in the header of any sketch you write for the sensor.
    Pins:
    MS5541 sensor attached to pins 10 - 13:
    MOSI: pin 11
    MISO: pin 12
    SCK: pin 13
    MCLK: pin 9
    CS is not in use, but might be pin 10
    created August 2011
    by SMStrauch based on application note AN510 from www.intersema.ch (http://www.meas-spec.com/downloads/Using_SPI_Protocol_with_Pressure_Sensor_Modules.pdf),
    and with help of robtillaart and ulrichard. Thanks!
    */

    // include library:
    #include <SPI.h>

    // generate a MCKL signal pin
    const int clock = 9;

    void resetsensor() //this function keeps the sketch a little shorter
    {
    SPI.setDataMode(SPI_MODE0);
    SPI.transfer(0x15);
    SPI.transfer(0x55);
    SPI.transfer(0x40);
    }

    void setup() {
    Serial.begin(9600);
    SPI.begin(); //see SPI library details on arduino.cc for details
    SPI.setBitOrder(MSBFIRST);
    SPI.setClockDivider(SPI_CLOCK_DIV32); //divide 16 MHz to communicate on 500 kHz
    pinMode(clock, OUTPUT);
    delay(100);
    }

    void loop()
    {
    TCCR1B = (TCCR1B & 0xF8) | 1 ; //generates the MCKL signal
    analogWrite (clock, 128) ;

    resetsensor();//resets the sensor - caution: afterwards mode = SPI_MODE0!

    //Calibration word 1
    unsigned int result1 = 0;
    unsigned int inbyte1 = 0;
    SPI.transfer(0x1D); //send first byte of command to get calibration word 1
    SPI.transfer(0x50); //send second byte of command to get calibration word 1
    SPI.setDataMode(SPI_MODE1); //change mode in order to listen
    result1 = SPI.transfer(0x00); //send dummy byte to read first byte of word
    result1 = result1 << 8; //shift returned byte
    inbyte1 = SPI.transfer(0x00); //send dummy byte to read second byte of word
    result1 = result1 | inbyte1; //combine first and second byte of word
    Serial.print("Calibration word 1 =");
    Serial.println(result1);

    resetsensor();//resets the sensor

    //Calibration word 2; see comments on calibration word 1
    unsigned int result2 = 0;
    byte inbyte2 = 0;
    SPI.transfer(0x1D);
    SPI.transfer(0x60);
    SPI.setDataMode(SPI_MODE1);
    result2 = SPI.transfer(0x00);
    result2 = result2 <<8;
    inbyte2 = SPI.transfer(0x00);
    result2 = result2 | inbyte2;
    Serial.print("Calibration word 2 =");
    Serial.println(result2);

    resetsensor();//resets the sensor

    //Calibration word 3; see comments on calibration word 1
    unsigned int result3 = 0;
    byte inbyte3 = 0;
    SPI.transfer(0x1D);
    SPI.transfer(0x90);
    SPI.setDataMode(SPI_MODE1);
    result3 = SPI.transfer(0x00);
    result3 = result3 <<8;
    inbyte3 = SPI.transfer(0x00);
    result3 = result3 | inbyte3;
    Serial.print("Calibration word 3 =");
    Serial.println(result3);

    resetsensor();//resets the sensor

    //Calibration word 4; see comments on calibration word 1
    unsigned int result4 = 0;
    byte inbyte4 = 0;
    SPI.transfer(0x1D);
    SPI.transfer(0xA0);
    SPI.setDataMode(SPI_MODE1);
    result4 = SPI.transfer(0x00);
    result4 = result4 <<8;
    inbyte4 = SPI.transfer(0x00);
    result4 = result4 | inbyte4;
    Serial.print("Calibration word 4 =");
    Serial.println(result4);

    //now we do some bitshifting to extract the calibration factors
    //out of the calibration words; read datasheet AN510 for better understanding
    long c1 = result1 >> 3 & 0x1FFF;
    long c2 = ((result1 & 0x07) << 10) | ((result2 >> 6) & 0x03FF);
    long c3 = (result3 >> 6) & 0x03FF;
    long c4 = (result4 >> 7) & 0x07FF;
    long c5 = ((result2 & 0x003F) << 6) | (result3 & 0x003F);
    long c6 = result4 & 0x007F;

    Serial.println(c1);
    Serial.println(c2);
    Serial.println(c3);
    Serial.println(c4);
    Serial.println(c5);
    Serial.println(c6);

    resetsensor();//resets the sensor

    //Temperature:
    unsigned int tempMSB = 0; //first byte of value
    unsigned int tempLSB = 0; //last byte of value
    unsigned int D2 = 0;
    SPI.transfer(0x0F); //send first byte of command to get temperature value
    SPI.transfer(0x20); //send second byte of command to get temperature value
    delay(35); //wait for conversion end
    SPI.setDataMode(SPI_MODE1); //change mode in order to listen
    tempMSB = SPI.transfer(0x00); //send dummy byte to read first byte of value
    tempMSB = tempMSB << 8; //shift first byte
    tempLSB = SPI.transfer(0x00); //send dummy byte to read second byte of value
    D2 = tempMSB | tempLSB; //combine first and second byte of value
    Serial.print("Temperature raw =");
    Serial.println(D2); //voilá!

    resetsensor();//resets the sensor

    //Pressure:
    unsigned int presMSB = 0; //first byte of value
    unsigned int presLSB =0; //last byte of value
    unsigned int D1 = 0;
    SPI.transfer(0x0F); //send first byte of command to get pressure value
    SPI.transfer(0x40); //send second byte of command to get pressure value
    delay(35); //wait for conversion end
    SPI.setDataMode(SPI_MODE1); //change mode in order to listen
    presMSB = SPI.transfer(0x00); //send dummy byte to read first byte of value
    presMSB = presMSB << 8; //shift first byte
    presLSB = SPI.transfer(0x00); //send dummy byte to read second byte of value
    D1 = presMSB | presLSB; //combine first and second byte of value
    Serial.print("Pressure raw =");
    Serial.println(D1);

    //calculation of the real values by means of the calibration factors and the maths
    //in the datasheet. const MUST be long
    const long UT1 = (c5 << 3) + 10000;
    const long dT = D2 - UT1;
    const long TEMP = 200 + ((dT * (c6 + 100)) >> 11);
    const long OFF = c2 + (((c4 - 250) * dT) >> 12) + 10000;
    const long SENS = (c1/2) + (((c3 + 200) * dT) >> 13) + 3000;
    long PCOMP = (SENS * (D1 - OFF) >> 12) + 1000;
    float TEMPREAL = TEMP/10;

    Serial.print("Real Temperature in °C=");
    Serial.println(TEMPREAL);

    Serial.print("Compensated pressure in mbar =");
    Serial.println(PCOMP);

    //2nd order compensation only for T > 0°C
    const long dT2 = dT - ((dT >> 7 * dT >> 7) >> 3);
    const float TEMPCOMP = (200 + (dT2*(c6+100) >>11))/10;
    Serial.print("2nd order compensated temperature in °C =");
    Serial.println(TEMPCOMP);

    delay(5000);
    }