GY-63_MS5611/libraries/MS5837/MS5837.cpp

280 lines
6.1 KiB
C++
Raw Normal View History

2023-12-24 05:16:46 -05:00
//
// FILE: MS5837.cpp
// AUTHOR: Rob Tillaart
// VERSION: 0.1.0
// DATE: 2023-11-12
// PURPOSE: Arduino library for MS5837 temperature and pressure sensor.
// URL: https://github.com/RobTillaart/MS5837
#include "MS5837.h"
// commands (MS5611 alike)
#define MS5837_CMD_READ_ADC 0x00
#define MS5837_CMD_READ_PROM 0xA0
#define MS5837_CMD_RESET 0x1E
#define MS5837_CMD_CONVERT_D1 0x4A // differs from MS5611
#define MS5837_CMD_CONVERT_D2 0x5A // differs from MS5611
// CONSTRUCTOR
MS5837::MS5837(TwoWire *wire)
{
_wire = wire;
}
bool MS5837::begin(uint8_t mathMode)
{
if (! isConnected()) return false;
reset(mathMode);
return true;
}
bool MS5837::isConnected()
{
_wire->beginTransmission(_address);
return ( _wire->endTransmission() == 0);
}
bool MS5837::reset(uint8_t mathMode)
{
command(MS5837_CMD_RESET);
uint32_t start = millis();
// while loop prevents blocking RTOS
while (micros() - start < 10)
{
yield();
delay(1);
}
initConstants(mathMode);
// SKIP CRC check
// derive the type from mathMode instead of the other way around.
// user must
_type = MS5837_TYPE_30;
if (mathMode == 1) _type = MS5837_TYPE_02;
if (mathMode == 2) _type = MS5803_TYPE_01;
return true;
}
uint8_t MS5837::getType()
{
return _type;
}
uint8_t MS5837::getAddress()
{
return _address;
}
//////////////////////////////////////////////////////////////////////
//
// READ
//
bool MS5837::read(uint8_t bits)
{
if (isConnected() == false) return false;
int index = constrain(bits, 8, 13);
index -= 8;
uint8_t waitMillis[6] = { 1, 2, 3, 5, 9, 18 };
uint8_t wait = waitMillis[index];
// D1 conversion
_wire->beginTransmission(_address);
_wire->write(MS5837_CMD_CONVERT_D1 + index * 2);
_wire->endTransmission(); // TODO check all of these
uint32_t start = millis();
// while loop prevents blocking RTOS
while (micros() - start < wait)
{
yield();
delay(1);
}
// NOTE: D1 and D2 are reserved in MBED (NANO BLE)
uint32_t _D1 = readADC();
// D2 conversion
_wire->beginTransmission(_address);
_wire->write(MS5837_CMD_CONVERT_D2 + index * 2);
_wire->endTransmission();
start = millis();
// while loop prevents blocking RTOS
while (micros() - start < wait)
{
yield();
delay(1);
}
// NOTE: D1 and D2 are reserved in MBED (NANO BLE)
uint32_t _D2 = readADC();
float dT = _D2 - C[5];
_temperature = 2000 + dT * C[6];
float offset = C[2] + dT * C[4];
float sens = C[1] + dT * C[3];
_pressure = _D1 * sens + offset;
// Second order compensation
if (_temperature < 20)
{
float ti = dT * dT * (11 * 2.91038304567E-11); // 1 / 2^35
float t = (_temperature - 2000) * (_temperature - 2000);
float offset2 = t * (31 * 0.125); // 1 / 2^3
float sens2 = t * (63 * 0.03125); // 1 / 2^5
offset -= offset2;
sens -= sens2;
_temperature -= ti;
}
// 1 / 2^21 C[7] / 100
_pressure = (_D1 * sens * 4.76837158203E-7 - offset) * C[7] * 0.01;
_temperature *= 0.01;
return true;
}
float MS5837::getPressure()
{
return _pressure;
}
float MS5837::getTemperature()
{
return _temperature;
}
// https://www.mide.com/air-pressure-at-altitude-calculator
// https://community.bosch-sensortec.com/t5/Question-and-answers/How-to-calculate-the-altitude-from-the-pressure-sensor-data/qaq-p/5702
//
float MS5837::getAltitude(float airPressure)
{
float ratio = _pressure / airPressure;
return 44330 * (1 - pow(ratio, 0.190294957));
}
//////////////////////////////////////////////////////////////////////
//
// DENSITY for depth
//
void MS5837::setDensity(float density)
{
_density = density;
}
float MS5837::getDensity()
{
return _density;
}
float MS5837::getDepth(float airPressure)
{
// 9.80665 == Gravity constant.
// 1 / (_density * 9.80665 * 10) can be pre-calculated and cached in setDensity.
//
// delta P = rho * g * h => h = delta P / rho * g
// pressure = mbar, density grams/cm3 => correction factor 0.1 (=1/10)
return (_pressure - airPressure)/(_density * 9.80665 * 10);
}
//////////////////////////////////////////////////////////////////////
//
// PROTECTED
//
int MS5837::command(uint8_t cmd)
{
yield();
_wire->beginTransmission(_address);
_wire->write(cmd);
_result = _wire->endTransmission();
return _result;
}
void MS5837::initConstants(uint8_t mathMode)
{
// Constants that were multiplied in read() - datasheet page 8
// do this once and you save CPU cycles.
//
// datasheet MS5837_30 page 7
//
// mathMode = 0; | = 1
C[0] = 1;
C[1] = 32768L; // SENSt1 = C[1] * 2^15 | * 2^16
C[2] = 65536L; // OFFt1 = C[2] * 2^16 | * 2^17
C[3] = 3.90625E-3; // TCS = C[3] / 2^8 | / 2^7
C[4] = 7.8125E-3; // TCO = C[4] / 2^7 | / 2^6
C[5] = 256; // Tref = C[5] * 2^8 | * 2^8
C[6] = 1.1920928955E-7; // TEMPSENS = C[6] / 2^23 | / 2^23
C[7] = 1.220703125E-4; // compensate uses / 2^13 | / 2^15
// Appnote version for pressure.
// adjustments for MS5837_02
if (mathMode == 1)
{
C[1] *= 2; // SENSt1
C[2] *= 2; // OFFt1
C[3] *= 2; // TCS
C[4] *= 2; // TCO
C[7] /= 4; // compensation code has factor 4.
}
// adjustments for MS5803_01
if (mathMode == 2)
{
C[7] /= 4; // compensation code has factor 4.
}
for (uint8_t i = 0; i < 7 ; i++)
{
_wire->beginTransmission(_address);
_wire->write(MS5837_CMD_READ_PROM + i + i);
_wire->endTransmission();
uint8_t length = 2;
_wire->requestFrom(_address, length);
uint16_t tmp = _wire->read() << 8;
tmp |= _wire->read();
C[i] *= tmp;
}
}
uint32_t MS5837::readADC()
{
command(MS5837_CMD_READ_ADC);
if (_result == 0)
{
uint8_t length = 3;
int bytes = _wire->requestFrom(_address, length);
if (bytes >= length)
{
uint32_t value = _wire->read() * 65536UL;
value += _wire->read() * 256UL;
value += _wire->read();
return value;
}
return 0UL;
}
return 0UL;
}
// -- END OF FILE --