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My MPL115A1 has M1PR XDOC written on it. What does this mean?

Question asked by Francis Benedict Baygan on Jan 26, 2014
Latest reply on Jan 27, 2014 by Francis Benedict Baygan

I noticed on my MPL115A1 that it has M1PR XDOC written on it. It doesnt even have the freescale logo and MPL115A1 written on it. What does this mean? Is it the same with other MPL115A1s? Ive been implementing it with a code from the internet but the values i get from the sensor is way off target.

 

Here is the code:

/*

MPL115A1 SPI Digital Barometer Test Code

Created on: September 30, 2010

  By: Jeremiah McConnell - miah at miah.com

Portions: Jim Lindblom - jim at sparkfun.com

 

This is a simple test program for the MPL115A1 Pressure Sensor (SPI version).

 

Hardware: ATmega168, ATmega328

Powered at 3.3V or 5V, running at 8MHz or 16MHz.

 

MPL115A1 Breakout ------------- Arduino

----------------- -------

  SDN ------------------- D9

  CSN ------------------- D10

  SDO ------------------- D12 *

  SDI ------------------- D11 *

  SCK ------------------- D13 *

  GND ------------------- GND

  VDD ------------------- VCC +

 

  * These pins physically connect to the SPI device so you can't change them

  + 5V board use 5V VDD, 3.3V board use 3.3V VDD

 

License: CCAv3.0 Attribution-ShareAlike (http://creativecommons.org/licenses/by-sa/3.0/)

You're free to use this code for any venture, but I'd love to hear about what you do with it,

and any awesome changes you make to it. Attribution is greatly appreciated.

*/

 

// Includes

#include <SPI.h>

 

// Get your current altimiter setting from from the National

// Weather Service - http://www.weather.gov

// This value is often labeled "Barometer" or "Barometric Pressure" or just "Pressure"

#define NWS_BARO 29.92

 

// Pin definitions

#define MPL115A1_ENABLE_PIN 9

#define MPL115A1_SELECT_PIN 10

 

// Masks for MPL115A1 SPI i/o

#define MPL115A1_READ_MASK  0x80

#define MPL115A1_WRITE_MASK 0x7F

 

// MPL115A1 register address map

#define PRESH   0x00   // 80

#define PRESL   0x02   // 82

#define TEMPH   0x04   // 84

#define TEMPL   0x06   // 86

 

#define A0MSB   0x08   // 88

#define A0LSB   0x0A   // 8A

#define B1MSB   0x0C   // 8C

#define B1LSB   0x0E   // 8E

#define B2MSB   0x10   // 90

#define B2LSB   0x12   // 92

#define C12MSB  0x14   // 94

#define C12LSB  0x16   // 96

#define C11MSB  0x18   // 98

#define C11LSB  0x1A   // 9A

#define C22MSB  0x1C   // 9C

#define C22LSB  0x1E   // 9E

 

// Unit conversion macros

#define FT_TO_M(x) ((long)((x)*(0.3048)))

#define KPA_TO_INHG(x) ((x)*(0.295333727))

#define KPA_TO_MMHG(x) ((x)*(7.50061683))

#define KPA_TO_PSIA(x) ((x)*(0.145037738))

#define KPA_TO_KGCM2(x) ((x)*(0.0102))

#define INHG_TO_PSIA(x) ((x)*(0.49109778))

#define DEGC_TO_DEGF(x) ((x)*(9.0/5.0)+32)

 

 

void setup() {

 

   // initialize serial i/o

   Serial.begin(9600);

 

   // initialize SPI interface

   SPI.begin();

 

   // these are the defaults

   //SPI.setDataMode(SPI_MODE0);

   //SPI.setClockDivider(SPI_CLOCK_DIV4); // MPL115A1 supports up to 8MHz

   //SPI.setBitOrder(MSBFIRST);

 

   // initialize the chip select and enable pins

   pinMode(MPL115A1_SELECT_PIN, OUTPUT);

   pinMode(MPL115A1_ENABLE_PIN, OUTPUT);

 

   // sleep the MPL115A1

   digitalWrite(MPL115A1_ENABLE_PIN, LOW);

 

   // set the chip select inactive, select signal is CS LOW

   digitalWrite(MPL115A1_SELECT_PIN, HIGH);

 

   // spam welcome banner

   Serial.print("\n************************************************************************************\n");

   Serial.print("* Using Altimiter Setting: ");

   Serial.print(NWS_BARO, 2);

   Serial.print(" in Hg *\n");

   Serial.print("* Visit http://www.weather.gov for your current local value. *\n");

   Serial.print("************************************************************************************\n");

}

 

 

void loop() {

 

   float pressure_pKa = 0;

   float temperature_c= 0;

   long altitude_ft = 0;

 

   // wake the MPL115A1

   digitalWrite(MPL115A1_ENABLE_PIN, HIGH);

   delay(20);  // give the chip a few ms to wake up

 

   pressure_pKa = calculatePressurekPa();

   temperature_c = calculateTemperatureC();

   altitude_ft = calculateAltitudeFt(pressure_pKa);

 

   // put the MPL115A1 to sleep, it has this feature why not use it

   // while in shutdown the part draws ~1uA

   digitalWrite(MPL115A1_ENABLE_PIN, LOW);

 

   // print table of altitude, pressures, and temperatures to console

   Serial.print(altitude_ft);

   Serial.print(" ft | ");

   Serial.print(FT_TO_M(altitude_ft));

   Serial.print(" m | ");

   Serial.print(KPA_TO_INHG(pressure_pKa), 2);

   Serial.print(" in Hg | ");

   Serial.print(KPA_TO_MMHG(pressure_pKa), 0);

   Serial.print(" mm Hg | ");

   Serial.print(KPA_TO_PSIA(pressure_pKa), 2);

   Serial.print(" psia | ");

   //Serial.print(KPA_TO_KGCM2(pressure_pKa), 3);

   ///Serial.print(" kg/cm2 | ");

   Serial.print(pressure_pKa, 1);

   Serial.print(" kPa | ");

 

   // At a res of -5.35 counts/°C, digits lower than 0.1°C are not significant

   Serial.print(temperature_c, 1);

   Serial.print(" C | ");

   Serial.print(DEGC_TO_DEGF(temperature_c), 1);

   Serial.print(" F\n");

 

   // wait a few seconds before looping

   delay(5000);

}

 

 

long calculateAltitudeFt(float pressure_kPa) {

 

   float delta;

   long altitude_ft;

 

 

   // See http://en.wikipedia.org/wiki/Barometric_formula

   // If you're a pilot you need to know what's going on here,

   // otherwise just know these steps calculate the barometric altitude (ft)

   // based on the ratio of absolute barometric pressure (psia) to the

   // altimiter setting (psia).

   delta = KPA_TO_PSIA(pressure_kPa) / INHG_TO_PSIA( NWS_BARO );

   altitude_ft = (1 - pow(delta, (1 / 5.25587611))) / 0.0000068756;

 

   return altitude_ft;

}

 

 

float calculateTemperatureC() {

 

   unsigned int uiTadc;

   unsigned char uiTH, uiTL;

 

   unsigned int temperature_counts = 0;

 

   writeRegister(0x22, 0x00);  // Start temperature conversion

   delay(2);   // Max wait time is 0.7ms, typ 0.6ms

 

   // Read pressure

   uiTH = readRegister(TEMPH);

   uiTL = readRegister(TEMPL);

 

   uiTadc = (unsigned int) uiTH << 8;

   uiTadc += (unsigned int) uiTL & 0x00FF;

 

   // Temperature is a 10bit value

   uiTadc = uiTadc >> 6;

 

   // -5.35 counts per °C, 472 counts is 25°C

   return 25 + (uiTadc - 472) / -5.35;

}

 

 

float calculatePressurekPa() {

 

   // See Freescale document AN3785 for detailed explanation

   // of this implementation.

 

   signed char sia0MSB, sia0LSB;

   signed char sib1MSB, sib1LSB;

   signed char sib2MSB, sib2LSB;

   signed char sic12MSB, sic12LSB;

   signed char sic11MSB, sic11LSB;

   signed char sic22MSB, sic22LSB;

   signed int sia0, sib1, sib2, sic12, sic11, sic22, siPcomp;

   float decPcomp;

   signed long lt1, lt2, lt3, si_c11x1, si_a11, si_c12x2;

   signed long si_a1, si_c22x2, si_a2, si_a1x1, si_y1, si_a2x2;

   unsigned int uiPadc, uiTadc;

   unsigned char uiPH, uiPL, uiTH, uiTL;

 

   writeRegister(0x24, 0x00);   // Start Both Conversions

   //writeRegister(0x20, 0x00); // Start Pressure Conversion

   //writeRegister(0x22, 0x00); // Start temperature conversion

   delay(2);   // Max wait time is 1ms, typ 0.8ms

 

   // Read pressure

   uiPH = readRegister(PRESH);

   uiPL = readRegister(PRESL);

   uiTH = readRegister(TEMPH);

   uiTL = readRegister(TEMPL);

 

   uiPadc = (unsigned int) uiPH << 8;

   uiPadc += (unsigned int) uiPL & 0x00FF;

   uiTadc = (unsigned int) uiTH << 8;

   uiTadc += (unsigned int) uiTL & 0x00FF;

 

   // Placing Coefficients into 16-bit Variables

   // a0

   sia0MSB = readRegister(A0MSB);

   sia0LSB = readRegister(A0LSB);

   sia0 = (signed int) sia0MSB << 8;

   sia0 += (signed int) sia0LSB & 0x00FF;

 

   // b1

   sib1MSB = readRegister(B1MSB);

   sib1LSB = readRegister(B1LSB);

   sib1 = (signed int) sib1MSB << 8;

   sib1 += (signed int) sib1LSB & 0x00FF;

 

   // b2

   sib2MSB = readRegister(B2MSB);

   sib2LSB = readRegister(B2LSB);

   sib2 = (signed int) sib2MSB << 8;

   sib2 += (signed int) sib2LSB & 0x00FF;

 

   // c12

   sic12MSB = readRegister(C12MSB);

   sic12LSB = readRegister(C12LSB);

   sic12 = (signed int) sic12MSB << 8;

   sic12 += (signed int) sic12LSB & 0x00FF;

 

   // c11

   sic11MSB = readRegister(C11MSB);

   sic11LSB = readRegister(C11LSB);

   sic11 = (signed int) sic11MSB << 8;

   sic11 += (signed int) sic11LSB & 0x00FF;

 

   // c22

   sic22MSB = readRegister(C22MSB);

   sic22LSB = readRegister(C22LSB);

   sic22 = (signed int) sic22MSB << 8;

   sic22 += (signed int) sic22LSB & 0x00FF;

 

   // Coefficient 9 equation compensation

   uiPadc = uiPadc >> 6;

   uiTadc = uiTadc >> 6;

 

   // Step 1 c11x1 = c11 * Padc

   lt1 = (signed long) sic11;

   lt2 = (signed long) uiPadc;

   lt3 = lt1*lt2;

   si_c11x1 = (signed long) lt3;

 

   // Step 2 a11 = b1 + c11x1

   lt1 = ((signed long)sib1)<<14;

   lt2 = (signed long) si_c11x1;

   lt3 = lt1 + lt2;

   si_a11 = (signed long)(lt3>>14);

 

   // Step 3 c12x2 = c12 * Tadc

   lt1 = (signed long) sic12;

   lt2 = (signed long) uiTadc;

   lt3 = lt1*lt2;

   si_c12x2 = (signed long)lt3;

 

   // Step 4 a1 = a11 + c12x2

   lt1 = ((signed long)si_a11<<11);

   lt2 = (signed long)si_c12x2;

   lt3 = lt1 + lt2;

   si_a1 = (signed long) lt3>>11;

 

   // Step 5 c22x2 = c22*Tadc

   lt1 = (signed long)sic22;

   lt2 = (signed long)uiTadc;

   lt3 = lt1 * lt2;

   si_c22x2 = (signed long)(lt3);

 

   // Step 6 a2 = b2 + c22x2

   lt1 = ((signed long)sib2<<15);

   lt2 = ((signed long)si_c22x2>1);

   lt3 = lt1+lt2;

   si_a2 = ((signed long)lt3>>16);

 

   // Step 7 a1x1 = a1 * Padc

   lt1 = (signed long)si_a1;

   lt2 = (signed long)uiPadc;

   lt3 = lt1*lt2;

   si_a1x1 = (signed long)(lt3);

 

   // Step 8 y1 = a0 + a1x1

   lt1 = ((signed long)sia0<<10);

   lt2 = (signed long)si_a1x1;

   lt3 = lt1+lt2;

   si_y1 = ((signed long)lt3>>10);

 

   // Step 9 a2x2 = a2 * Tadc

   lt1 = (signed long)si_a2;

   lt2 = (signed long)uiTadc;

   lt3 = lt1*lt2;

   si_a2x2 = (signed long)(lt3);

 

   // Step 10 pComp = y1 + a2x2

   lt1 = ((signed long)si_y1<<10);

   lt2 = (signed long)si_a2x2;

   lt3 = lt1+lt2;

 

   // Fixed point result with rounding

   //siPcomp = ((signed int)lt3>>13);

   siPcomp = lt3/8192;

 

   // decPcomp is defined as a floating point number

   // Conversion to decimal value from 1023 ADC count value

   // ADC counts are 0 to 1023, pressure is 50 to 115kPa respectively

   decPcomp = ((65.0/1023.0)*siPcomp)+50;

 

   return decPcomp;

}

 

 

unsigned int readRegister(byte thisRegister) {

 

   byte result = 0;

 

   // select the MPL115A1

   digitalWrite(MPL115A1_SELECT_PIN, LOW);

 

   // send the request

   SPI.transfer(thisRegister | MPL115A1_READ_MASK);

   result = SPI.transfer(0x00);

 

   // deselect the MPL115A1

   digitalWrite(MPL115A1_SELECT_PIN, HIGH);

 

   return result;

}

 

 

void writeRegister(byte thisRegister, byte thisValue) {

 

   // select the MPL115A1

   digitalWrite(MPL115A1_SELECT_PIN, LOW);

 

   // send the request

   SPI.transfer(thisRegister & MPL115A1_WRITE_MASK);

   SPI.transfer(thisValue);

 

   // deselect the MPL115A1

   digitalWrite(MPL115A1_SELECT_PIN, HIGH);

}

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