+ 0.1.04

+ changed float to double (for platforms which support it) + changed divisions in multiplications + fixed uint32_t readADC() + reduced size of C array by 1 float + added second order temperature compensation

Author: RobTillaart

libraries/MS5611/MS5611.cpp

@@ -2,11 +2,16 @@
 // FILE: MS5611.cpp
 // AUTHOR: Rob Tillaart
 // Erni - testing/fixes
-// VERSION: 0.1.03
+// VERSION: 0.1.04
 // PURPOSE: MS5611 Temperature & Humidity library for Arduino
 // URL:
 //
 // HISTORY:
+// 0.1.04 changed float to double (for platforms which support it)
+// changed divisions in multiplications
+// fixed uint32_t readADC()
+// reduced size of C array by 1 float
+// added second order temperature compensation
 // 0.1.03 changed math to float [test version]
 // 0.1.02 fixed bug return value read()
 // fixed bug #bits D2
@@ -39,8 +44,10 @@ MS5611::MS5611(uint8_t address)
 void MS5611::init()
 {
  reset();
- for (int reg = 0; reg < 8; reg++)
+ for (int reg = 0; reg < 7; reg++)
  {
+ // C[0] not used; this way indices match datasheet.
+ // C[7] == CRC skipped.
  C[reg] = readProm(reg);
  }
 }
@@ -50,21 +57,47 @@ int MS5611::read(uint8_t bits)
  // VARIABLES NAMES BASED ON DATASHEET
  convert(0x40, bits);
  if (_result) return _result;
- int32_t D1 = readADC();
+ uint32_t D1 = readADC();
  if (_result) return _result;
 
  convert(0x50, bits);
  if (_result) return _result;
- int32_t D2 = readADC();
+ uint32_t D2 = readADC();
  if (_result) return _result;
 
- // PAGE 7/20 of the datasheet
- float dT = D2 - (C[5] * 256L);
- _temperature = 2000 + (dT * C[6])/8388608L;
+ // TODO the multiplications of these constants can be done in init()
+ // but first they need to be verified.
+ 
+ // TEMP & PRESS MATH - PAGE 7/20
+ double dT = D2 - C[5] * 256L;
+ _temperature = 2000 + dT * C[6] * 1.1920928955E-7;
 
- float offset = (C[2] * 65536L) + (C[4] * dT ) / 128L;
- float sens = C[1] * 32768L + (C[3] * dT ) / 256L;
- _pressure = (((D1 * sens)/2097152L) - offset) / 32768L;
+ double offset = C[2] * 65536L + dT * C[4] * 7.8125E-3;
+ double sens = C[1] * 32768L + dT * C[3] * 3.90625E-3;
+
+ // SECOND ORDER COMPENSATION - PAGE 8/20
+ // COMMENT OUT < 20 CORRECTION IF NOT NEEDED
+ if (_temperature < 20)
+ {
+ double T2 = dT * dT * 4.6566128731E-10;
+ double t = _temperature - 2000;
+ double offset2 = 2.5 * t * t;
+ double sens2 = 1.25 * t * t * t;
+ // COMMENT OUT < -15 CORRECTION IF NOT NEEDED
+ if (_temperature < -15)
+ {
+ t = _temperature + 1500;
+ t = t * t;
+ offset2 += 7 * t;
+ sens2 += 5.5 * t;
+ }
+ _temperature -= T2;
+ offset -= offset2;
+ sens -= sens2;
+ }
+ // END SECOND ORDER COMPENSATION
+
+ _pressure = (D1 * sens * 4.76837158205E-7 - offset) * 3.051757813E-5;
 
  return 0;
 }
@@ -108,7 +141,7 @@ uint16_t MS5611::readProm(uint8_t reg)
  return 0;
 }
 
-int32_t MS5611::readADC()
+uint32_t MS5611::readADC()
 {
  command(0x00);
  if (_result == 0)

libraries/MS5611/MS5611.h

@@ -2,7 +2,7 @@
 // FILE: MS5611.h
 // AUTHOR: Rob Tillaart
 // Erni - testing/fixes
-// VERSION: 0.1.03
+// VERSION: 0.1.04
 // PURPOSE: MS5611 Temperature & Pressure library for Arduino
 // URL:
 //
@@ -20,7 +20,7 @@
 #include <Arduino.h>
 #endif
 
-#define MS5611_LIB_VERSION "0.1.03"
+#define MS5611_LIB_VERSION "0.1.04"
 
 #define MS5611_READ_OK 0
 
@@ -38,15 +38,16 @@ class MS5611
 private:
  void reset();
  void convert(uint8_t ADDR, uint8_t bits);
- int32_t  readADC();
+ uint32_t readADC();
  uint16_t readProm(uint8_t reg);
  void command(uint8_t command);
 
  uint8_t _address;
  int32_t _temperature;
  int32_t _pressure;
  int _result;
- float C[8];
+ double C[7];
+
 };
 #endif
 //