http://hackaweek.com/hacks/?p=1021
#ifndef INTERSEMA_BARO_H
#define INTERSEMA_BARO_H
#include <Wire.h>
#include <util/delay.h>
#include "Arduino.h"
namespace Intersema
{
class BaroPressure
{
public:
virtual void init() = 0;
int32_t getHeightCentiMeters(void)
{
return AcquireAveragedSampleCm(NUM_SAMP_FOR_AVG);
}
protected:
virtual int32_t AcquireAveragedSampleCm(const uint8_t nSamples) = 0;
virtual uint32_t ConvertPressureTemperature(uint32_t pressure, uint32_t temperature) = 0;
int32_t PascalToCentimeter(const int32_t pressurePa)
{
// Lookup table converting pressure in Pa to altitude in cm.
// Each LUT entry is the altitude in cm corresponding to an implicit
// pressure value, calculated as [PA_INIT - 1024*index] in Pa.
// The table is calculated for a nominal sea-level pressure = 101325 Pa.
static const int32_t PZLUT_ENTRIES = 77;
static const int32_t PA_INIT = 104908;
static const int32_t PA_DELTA = 1024;
static const int32_t lookupTable[PZLUT_ENTRIES] = {
-29408, -21087, -12700, -4244, 4279,
12874, 21541, 30281, 39095, 47986,
56953, 66000, 75126, 84335, 93628,
103006, 112472, 122026, 131672, 141410,
151244, 161174, 171204, 181335, 191570,
201911, 212361, 222922, 233597, 244388,
255300, 266334, 277494, 288782, 300204,
311761, 323457, 335297, 347285, 359424,
371719, 384174, 396795, 409586, 422552,
435700, 449033, 462560, 476285, 490216,
504360, 518724, 533316, 548144, 563216,
578543, 594134, 609999, 626149, 642595,
659352, 676431, 693847, 711615, 729752,
748275, 767202, 786555, 806356, 826627,
847395, 868688, 890537, 912974, 936037,
959766, 984206};
if(pressurePa > PA_INIT)
return lookupTable[0];
else
{
const int32_t inx = (PA_INIT - pressurePa) >> 10;
if(inx >= PZLUT_ENTRIES - 1)
return lookupTable[PZLUT_ENTRIES - 1];
else
{
const int32_t pa1 = PA_INIT - (inx << 10);
const int32_t z1 = lookupTable[inx];
const int32_t z2 = lookupTable[inx+1];
return (z1 + (((pa1 - pressurePa) * (z2 - z1)) >> 10));
}
}
}
static const uint8_t NUM_SAMP_FOR_AVG = 4;
unsigned int coefficients_[6];
};
class BaroPressure_MS5607B : public BaroPressure
{
public:
/// @param CSB i2c address select
BaroPressure_MS5607B(bool CSB = false) : i2cAddr_((CSB ? 0xEC : 0xEE) >> 1) { }
void init()
{
ResetSensor();
ReadCoefficients();
}
private:
const uint8_t i2cAddr_;
static const uint8_t cmdReset_ = 0x1E;
static const uint8_t cmdAdcRead_ = 0x00;
static const uint8_t cmdAdcConv_ = 0x40;
static const uint8_t cmdAdcD1_ = 0x00;
static const uint8_t cmdAdcD2_ = 0x10;
static const uint8_t cmdAdc256_ = 0x00;
static const uint8_t cmdAdc512_ = 0x02;
static const uint8_t cmdAdc1024_ = 0x04;
static const uint8_t cmdAdc2048_ = 0x06;
static const uint8_t cmdAdc4096_ = 0x08;
static const uint8_t cmdPromRd_ = 0xA0;
void ResetSensor()
{
Wire.begin();
Wire.beginTransmission(i2cAddr_);
Wire.write(cmdReset_);
Wire.endTransmission();
delay(3);
}
void ReadCoefficients(void)
{
for(uint8_t i=0; i<6; ++i)
coefficients_ *= ReadCoefficient(i + 1); *
#ifdef DEBUG
- for(uint8_t i=0; i<6; ++i)*
- {*
- Serial.print("Coefficient ");*
- Serial.print(i + 1, DEC);*
- Serial.print(" : ");*
Serial.println(coefficients_, DEC);
* }*
* Serial.println(ConvertPressureTemperature(6074082, 8574974));*
* Serial.println(ConvertPressureTemperature(6074082, 8574984));*
#endif
* }*
* uint16_t ReadCoefficient(const uint8_t coefNum)
_ {_
uint16_t rC=0;*
* Wire.beginTransmission(i2cAddr_);
Wire.write(cmdPromRd_ + coefNum * 2); // send PROM READ command
_ Wire.endTransmission();*_
* Wire.requestFrom(i2cAddr_, static_cast<uint8_t>(2));
_ if(Wire.available() >= 2)_
_ {_
uint16_t ret = Wire.read(); // read MSB and acknowledge*
uint16_t rC = 256 * ret;
* ret = Wire.read(); // read LSB and not acknowledge*
* rC = rC + ret;*
* return rC;*
* }*
#ifdef DEBUG
* else*
* {*
* Serial.println("No data available in ReadCoefficient()");*
* }*
#endif
* return 0;*
* }*
* virtual int32_t AcquireAveragedSampleCm(const uint8_t nSamples)
_ {_
int64_t pressAccum = 0;
for(size_t n = nSamples; n; n--)
_ {_
const uint32_t temperature = ReadAdc(cmdAdcD2_ | cmdAdc4096_); // digital temperature value : typical 8077636
const uint32_t pressure = ReadAdc(cmdAdcD1_ | cmdAdc4096_); // digital pressure value : typical 6465444
const uint32_t pressConv = ConvertPressureTemperature(pressure, temperature);
_ pressAccum += pressConv;_
_/
* //MAPGPS*
* Serial.print("pressure: ");*
* Serial.print(pressure, DEC);*
* Serial.print(", pressConv: ");*
* Serial.print(pressConv, DEC);*
* Serial.print(", temperature: ");*
* Serial.println(temperature, DEC);*
/_
_ }_
const int32_t pressAvg = pressAccum / nSamples;
const int32_t AltCm = PascalToCentimeter(pressAvg);*
* return AltCm; *
* }*
* int32_t ReadAdc(const uint8_t cmd)
_ { _
Wire.beginTransmission(i2cAddr_);
Wire.write(cmdAdcConv_ | cmd); // send conversion command*
* Wire.endTransmission();*
* // wait necessary conversion time*
* switch(cmd & 0x0f)*
* {*
* case cmdAdc256_:
_ delay(1);_
_ break;_
case cmdAdc512_:
_ delay(3);_
_ break;_
case cmdAdc1024_:
_ delay(4);_
_ break;_
case cmdAdc2048_:
_ delay(6);_
_ break;_
case cmdAdc4096_:
_ delay(10);_
_ break;_
_ }_
Wire.beginTransmission(i2cAddr_);
Wire.write(cmdAdcRead_);
_ Wire.endTransmission();*_
* Wire.requestFrom(i2cAddr_, static_cast<uint8_t>(3));
_ if(Wire.available() >= 3)_
_ {_
uint16_t ret = Wire.read(); // read MSB and acknowledge*
uint32_t temp = 65536 * ret;
* ret = Wire.read(); // read byte and acknowledge*
_ temp = temp + 256 * ret;_
* ret = Wire.read(); // read LSB and not acknowledge*
* temp = temp + ret;*
* return temp;*
* }*
#ifdef DEBUG
* else*
* {*
* Serial.println("No data available in cmdAdc()");*
* }*
#endif
* return 0;*
* }*
* uint32_t ConvertPressureTemperature(uint32_t pressure, uint32_t temperature)
_ {_
_ // calcualte 1st order pressure and temperature (MS5607 1st order algorithm)*_
const int32_t dT = temperature - coefficients_[4] * 256; // difference between actual and reference temperature
//const int32_t temp = (2000 + (dT * coefficients_[5]) / pow(2, 23)) ; // / 100; // actual temperature
//const int64_t OFF = static_cast<int64_t>(coefficients_[1]) * pow(2, 17) + dT * coefficients_[3] / pow(2, 6); // offset at actual temperature
//const int64_t SENS = static_cast<int64_t>(coefficients_[0]) * pow(2, 16) + dT * coefficients_[2] / pow(2, 7); // sensitivity at actual temperature
//const int32_t press = ((pressure * SENS / pow(2, 21) - OFF) / pow(2, 15)); // / 100; // temperature compensated pressure
* //MAPGPS: adapt formulas to avoid overflow*
const int32_t OFF = coefficients_[1] * 4 + ((float)dT / 2048) * ((float)coefficients_[3] / 1024);
const int32_t SENS = coefficients_[0] * 2 + ((float)dT / 4096) * ((float)coefficients_[2] / 1024);
const int32_t press = ((float)pressure / 2048) * ((float)SENS / 1024) - OFF;
/*
* Serial.println();*
* Serial.println(dT, DEC);*
* Serial.println(OFF, DEC);*
* Serial.println(SENS, DEC);*
* Serial.println();*
*/
* return press;*
* }*
};
} // namespace Intersema
#endif
