Depth Sensor Code - modified j.brian

depth_sensor.ino

/*
created August 2011
by SMStrauch and with help of robtillaart and ulrichard. Thanks!

Manufacturer: www.intersema.ch
Source: http://www.meas-spec.com/downloads/Using_SPI_Protocol_with_Pressure_Sensor_Modules.pdf
Source: http://forum.arduino.cc/index.php?topic=67188.0
Datasheet: http://media.digikey.com/pdf/Data%20Sheets/Measurement%20Specialties%20PDFs/MS5541-CM.pdf

Modified 2-10-2015 J.Brian

MS5541 Pressure Sensor calwords readout
This program will read your MS5441 or compatible pressure sensor every 5 seconds and show you:
calibration words
calibration factors 
raw values 
and compensated values of temperature and pressure


Assumed pressure and temp. range: 0...14 bar, -40...85°C

Pins:
MS5541 sensor attached to pins 9, 11 - 13:

SPI : Arduino Pin : MS5541
--------------------------
MOSI:      11     :  DIN
MISO:      12     :  DOUT
SCK :      13     :  SCKL
MCLK:       9     :  MCLK
CS  :    N/C(10)  :  N/A

Calibration Words 1-4 16-bit

Source: http://www.amsys.info/sheets/amsys.en.an518_e.pdf

Coefficients:
  Name  :               Value                :  Bits :  MIN  :   TYP  :   MAX  :  Variable Name :
   C1   :  Pressure Sensitivity              :   13  :   0   :  2391  :  8191  :     SENST1     :
   C2   :  Pressure Offset                   :   13  :   0   :  4888  :  8191  :     OFFT1      :
   C3   :  Temp. Coef. of Press. Sensitivity :   10  :   0   :   385  :  1023  :      TCS       :
   C4   :  Temp. Coef. of Press. Offset      :    9  :   0   :   221  :   511  :      TCO       :
   C5   :  Ref. Temp.                        :   12  :   0   :  1689  :  4095  :      Tref      :
   C6   :  Temp Coef. of Temp.               :    7  :   0   :    58  :   127  :    TEMPSENS    :

Digital Pressure & Temp.:
Variable Name:        Value          :  Bits  :  MIN  :  TYP  :  MAX  :
     D1      :  Digital Pressure     :   16   :   0   : 17000 : 40000 :
     D2      :  Digital Temperature  :   16   :   0   : 27000 : 45000 :
     
Maximum Values for Calculation Results
Pmin = 0mbar
Pmax = 14bar

Tmin = -40°C
Tmax = +85°C
Tref = +20°C
                                                :   MIN   :  TYP  :  MAX  :
UT1 = 8 * C5 + 10000                            :  10000  : 28016 : 42760 :
dUT = D2 - UT1                                  : -11400  :   0   : 12350 :
** dTmin = (Tmin - Tref) * 190TLSB / °C
** dTmax = (Tmax - Tref) * 190TLSB / °C

OFF = C2 + 10000 + (C4-250) * dUT / 2^12        :  9246   : 14888 : 18887 :
** OFFmin = C2min + 10000 + (C4min - 250) * dTmax / 2^12
** OFFmax = C2max + 10000 + (C4max - 250) * dTmin / 2^12

SENS = C1 / 2 + (C3 + 200) * dUT / 2^13 + 3000  :  1298   :  4196 :  8939 :
**SENSmin = C1min / 2 + (C3max + 200) * dTmin / 2^13 + 3000
**SENSmax = C1max / 2 + (C3max + 200) * dTmax / 2^13 + 3000

P(0...14bar, with 1mbar resolution)             :    0    :       : 14000 :

TEMP = 200 + dT * (C6 + 100) / 2 ^ 11           :  -400   :       :   850 :
**(-40...85°C, with 0.1 °C resolution, in 0.1 °C units)

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

//*******************************************************************
//One of the following defines have to be uncommented but never both

//If Coeffecients have ben set:
#define CONSTANTS_SET true

//otherwise
//#define CALIBRATION true;
//********************************************************************




#ifdef CONSTANTS_SET
  const long SENST1 = 63;
  const long OFFT = 8077;
  const long TCS = 386;
  const long TCO = 234;
  const long Tref = 2097;
  const long TEMPSENS = 55;
#endif

#ifdef CALIBRATION
  long SENST1 = 2723;
  long OFFT = 4648;
  long TCS = 388;
  long TCO = 224;
  long Tref = 2309;
  long TEMPSENS = 54;
#endif

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

//Hex Values for writing to MS5541
byte D1_HIGH = 0x0F;
byte D1_LOW = 0x40;
byte D2_HIGH = 0x0F;
byte D2_LOW = 0x20;
byte W1_HIGH = 0x1D;
byte W1_LOW = 0x50;
byte W2_HIGH = 0x1D;
byte W2_LOW = 0x60;
byte W3_HIGH = 0x1D;
byte W3_LOW = 0x90;
byte W4_HIGH = 0x1D;
byte W4_LOW = 0xA0;
byte DUMMY = 0x00;

unsigned int word_1 = 0;
unsigned int word_2 = 0;
unsigned int word_3 = 0;
unsigned int word_4 = 0;
byte inByte_low = 0x00;

unsigned int D1 = 0;
unsigned int D2 = 0;

long UT1 = 0;
long dT = 0;
long TEMP = 0;
long OFF  = 0;
long SENS = 0;
long PCOMP = 0;
float TEMPREAL = 0;
long dT2 = 0;
float TEMPCOMP = 0;

void Reset_Sequence_Command();
#ifdef CALIBRATION
  void getCValues();
  void getCalibrationWords();
#endif
void getDigitalValues();
void getRealValues();

void setup() {
   Serial.begin(9600);
   SPI.begin(); 
   
   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 & B11111000 | B00000001; //generates the MCKL signal
   analogWrite(clock, 128) ; 
   
   #ifdef CALIBRATION
     getCalibrationWords();
     getCValues();
   #endif
   
   getDigitalValues();
   getRealValues();
  
   delay(500);
}

void Reset_Sequence_Command() {
   SPI.setDataMode(SPI_MODE0); 
   SPI.transfer(0x15);
   SPI.transfer(0x55);
   SPI.transfer(0x40);
}

#ifdef CALIBRATION
void getCalibrationWords() {
//Calibration word 1
 SPI.transfer(W1_HIGH); 
 SPI.transfer(W1_LOW);
 
 SPI.setDataMode(SPI_MODE1); 
 word_1 = SPI.transfer(DUMMY); 
 word_1 = word_1 << 8; 
 inByte_low = SPI.transfer(DUMMY); 
 word_1 = word_1 | inByte_low; 
 
 Reset_Sequence_Command();//resets the sensor

 //Calibration word 2; 
 SPI.transfer(W2_HIGH);
 SPI.transfer(W2_LOW);
 
 SPI.setDataMode(SPI_MODE1); 
 word_2 = SPI.transfer(DUMMY);
 word_2 = word_2 << 8;
 inByte_low = SPI.transfer(DUMMY);
 word_2 = word_2 | inByte_low;

 Reset_Sequence_Command();//resets the sensor

 //Calibration word 3; 
 SPI.transfer(W3_HIGH);
 SPI.transfer(W3_LOW);
 
 SPI.setDataMode(SPI_MODE1); 
 word_3 = SPI.transfer(DUMMY);
 word_3 = word_3 << 8;
 inByte_low = SPI.transfer(DUMMY);
 word_3 = word_3 | inByte_low; 

 Reset_Sequence_Command();//resets the sensor

 //Calibration word 4; 
 SPI.transfer(W4_HIGH);
 SPI.transfer(W4_LOW);
 
 SPI.setDataMode(SPI_MODE1); 
 word_4 = SPI.transfer(DUMMY);
 word_4 = word_4 << 8;
 inByte_low = SPI.transfer(DUMMY);
 word_4 = word_4 | inByte_low;
 
 Serial.print("Calibration word 1 =");
 Serial.println(word_1);
 
 Serial.print("Calibration word 2 =");
 Serial.println(word_2);  
 
 Serial.print("Calibration word 3 =");
 Serial.println(word_3); 
 
 Serial.print("Calibration word 4 =");
 Serial.println(word_4);
}
#endif 

#ifdef CALIBRATION
void getCValues() {
     //now we do some bitshifting to extract the calibration factors 
     //out of the calibration words; read datasheet AN510 for better understanding
     SENST1 = word_1 >> 3 & 0x1FFF;
     OFFT = ((word_1 & 0x07) << 10) | ((word_2 >> 6) & 0x03FF);
     TCS = (word_3 >> 6) & 0x03FF;
     TCO = (word_4 >> 7) & 0x07FF;
     Tref = ((word_2 & 0x003F) << 6) | (word_3 & 0x003F);
     TEMPSENS = word_4 & 0x007F;
     
     Reset_Sequence_Command();
     
     Serial.print("SENST1   (C1): ");
     Serial.println(SENST1);
     Serial.print("OFFT     (C2): ");
     Serial.println(OFFT);
     Serial.print("TCS      (C3): ");
     Serial.println(TCS);
     Serial.print("TCO      (C4): ");
     Serial.println(TCO);
     Serial.print("Tref     (C5): ");
     Serial.println(Tref);
     Serial.print("TEMPSENS (C6): ");
     Serial.println(TEMPSENS);
  }
#endif

void getDigitalValues() { 
   
   Reset_Sequence_Command();
   
   //Pressure (D1):
   SPI.transfer(D1_HIGH); 
   SPI.transfer(D1_LOW); 
   //delay(35);
   
   SPI.setDataMode(SPI_MODE1); 
   D1 = SPI.transfer(DUMMY); 
   D1 = D1 << 8; 
   inByte_low = SPI.transfer(DUMMY); 
   D1 = D1 | inByte_low; 
   
   Serial.print("Pressure raw =");
   Serial.println(D1);
   
   Reset_Sequence_Command();
   
   //Temperature (D2):
   SPI.transfer(D2_HIGH); 
   SPI.transfer(D2_LOW); 
   //delay(35);
   
   SPI.setDataMode(SPI_MODE1); 
   D2 = SPI.transfer(DUMMY); 
   D2 = D2 << 8; 
   inByte_low = SPI.transfer(DUMMY); 
   D2 = D2 | inByte_low; 
   
   Serial.print("Temperature raw =");
   Serial.println(D2);   
}

void getRealValues() {
   //calculation of the real values by means of the calibration factors 
   UT1 = (Tref << 3) + 10000;
   dT = D2 - UT1;
   TEMP = 200 + ((dT * (TEMPSENS + 100)) >> 11);
   OFF  = OFFT + (((TCO - 250) * dT) >> 12) + 10000;
   SENS = (SENST1/2) + (((TCS + 200) * dT) >> 13) + 3000;
   PCOMP = (SENS * (D1 - OFF) >> 12) + 1000;
   TEMPREAL = TEMP/10;
  
   //2nd order compensation only for T > 0°C
   dT2 = dT - ((dT >> 7 * dT >> 7) >> 3);
   TEMPCOMP = (200 + (dT2*(TEMPSENS+100) >>11))/10;
   
   Serial.print("Real Temperature in °C=");
   Serial.println(TEMPREAL);
  
   Serial.print("Compensated pressure in mbar =");
   Serial.println(PCOMP);
   
   Serial.print("2nd order compensated temperature in °C =");
   Serial.println(TEMPCOMP);  
   Serial.println();
}