SparkFunBME280.cpp

/******************************************************************************
SparkFunBME280.cpp
BME280 Particle Photon and Core Driver
Orginal by: Marshall Taylor @ SparkFun Electronics
Particle adaption by: Markus Haack (https://github.com/mhaack)
https://github.com/mhaack/SparkFun_BME280

Development environment specifics:
Particle IDE or Web IDE

This code is released under the [MIT License](http://opensource.org/licenses/MIT).
Please review the LICENSE.md file included with this example. If you have any questions
or concerns with licensing, please contact techsupport@sparkfun.com.
Distributed as-is; no warranty is given.
******************************************************************************/
//See SparkFunBME280.h for additional topology notes.

#include "SparkFunBME280.h"
#include "application.h"
#include <math.h>

//****************************************************************************//
//
//  Settings and configuration
//
//****************************************************************************//

//Constructor -- Specifies default configuration
BME280::BME280( void )
{
	//Construct with these default settings if nothing is specified

	//Select interface mode
	settings.commInterface = I2C_MODE; //Can be I2C_MODE, SPI_MODE
	//Select address for I2C.  Does nothing for SPI
	settings.I2CAddress = 0x77; //Ignored for SPI_MODE
	//Select CS pin for SPI.  Does nothing for I2C
	settings.chipSelectPin = 10;
	settings.runMode = 0;
	settings.tempOverSample = 0;
	settings.pressOverSample = 0;
	settings.humidOverSample = 0;

}


//****************************************************************************//
//
//  Configuration section
//
//  This uses the stored SensorSettings to start the IMU
//  Use statements such as "mySensor.settings.commInterface = SPI_MODE;" to
//  configure before calling .begin();
//
//****************************************************************************//
uint8_t BME280::begin()
{
	//Check the settings structure values to determine how to setup the device
	uint8_t dataToWrite = 0;  //Temporary variable

	switch (settings.commInterface)
	{

	case I2C_MODE:
		Wire.begin();
		break;

	case SPI_MODE:
		// start the SPI library:
		SPI.begin();
		// Maximum SPI frequency is 10MHz, could divide by 2 here:
		SPI.setClockDivider(SPI_CLOCK_DIV32);
		// Data is read and written MSb first.
		SPI.setBitOrder(MSBFIRST);
		// Data is captured on rising edge of clock (CPHA = 0)
		// Base value of the clock is HIGH (CPOL = 1)
		// This was SPI_MODE3 for RedBoard, but I had to change to
		// MODE0 for Teensy 3.1 operation
		SPI.setDataMode(SPI_MODE3);
		// initalize the  data ready and chip select pins:
		pinMode(settings.chipSelectPin, OUTPUT);
		digitalWrite(settings.chipSelectPin, HIGH);
		break;

	default:
		break;
	}

	//Reading all compensation data, range 0x88:A1, 0xE1:E7

	calibration.dig_T1 = ((uint16_t)((readRegister(BME280_DIG_T1_MSB_REG) << 8) + readRegister(BME280_DIG_T1_LSB_REG)));
	calibration.dig_T2 = ((int16_t)((readRegister(BME280_DIG_T2_MSB_REG) << 8) + readRegister(BME280_DIG_T2_LSB_REG)));
	calibration.dig_T3 = ((int16_t)((readRegister(BME280_DIG_T3_MSB_REG) << 8) + readRegister(BME280_DIG_T3_LSB_REG)));

	calibration.dig_P1 = ((uint16_t)((readRegister(BME280_DIG_P1_MSB_REG) << 8) + readRegister(BME280_DIG_P1_LSB_REG)));
	calibration.dig_P2 = ((int16_t)((readRegister(BME280_DIG_P2_MSB_REG) << 8) + readRegister(BME280_DIG_P2_LSB_REG)));
	calibration.dig_P3 = ((int16_t)((readRegister(BME280_DIG_P3_MSB_REG) << 8) + readRegister(BME280_DIG_P3_LSB_REG)));
	calibration.dig_P4 = ((int16_t)((readRegister(BME280_DIG_P4_MSB_REG) << 8) + readRegister(BME280_DIG_P4_LSB_REG)));
	calibration.dig_P5 = ((int16_t)((readRegister(BME280_DIG_P5_MSB_REG) << 8) + readRegister(BME280_DIG_P5_LSB_REG)));
	calibration.dig_P6 = ((int16_t)((readRegister(BME280_DIG_P6_MSB_REG) << 8) + readRegister(BME280_DIG_P6_LSB_REG)));
	calibration.dig_P7 = ((int16_t)((readRegister(BME280_DIG_P7_MSB_REG) << 8) + readRegister(BME280_DIG_P7_LSB_REG)));
	calibration.dig_P8 = ((int16_t)((readRegister(BME280_DIG_P8_MSB_REG) << 8) + readRegister(BME280_DIG_P8_LSB_REG)));
	calibration.dig_P9 = ((int16_t)((readRegister(BME280_DIG_P9_MSB_REG) << 8) + readRegister(BME280_DIG_P9_LSB_REG)));

	calibration.dig_H1 = ((uint8_t)(readRegister(BME280_DIG_H1_REG)));
	calibration.dig_H2 = ((int16_t)((readRegister(BME280_DIG_H2_MSB_REG) << 8) + readRegister(BME280_DIG_H2_LSB_REG)));
	calibration.dig_H3 = ((uint8_t)(readRegister(BME280_DIG_H3_REG)));
	calibration.dig_H4 = ((int16_t)((readRegister(BME280_DIG_H4_MSB_REG) << 4) + (readRegister(BME280_DIG_H4_LSB_REG) & 0x0F)));
	calibration.dig_H5 = ((int16_t)((readRegister(BME280_DIG_H5_MSB_REG) << 4) + ((readRegister(BME280_DIG_H4_LSB_REG) >> 4) & 0x0F)));
	calibration.dig_H6 = ((uint8_t)readRegister(BME280_DIG_H6_REG));

	//Set the oversampling control words.
	//config will only be writeable in sleep mode, so first insure that.
	writeRegister(BME280_CTRL_MEAS_REG, 0x00);

	//Set the config word
	dataToWrite = (settings.tStandby << 0x5) & 0xE0;
	dataToWrite |= (settings.filter << 0x02) & 0x1C;
	writeRegister(BME280_CONFIG_REG, dataToWrite);

	//Set ctrl_hum first, then ctrl_meas to activate ctrl_hum
	dataToWrite = settings.humidOverSample & 0x07; //all other bits can be ignored
	writeRegister(BME280_CTRL_HUMIDITY_REG, dataToWrite);

	//set ctrl_meas
	//First, set temp oversampling
	dataToWrite = (settings.tempOverSample << 0x5) & 0xE0;
	//Next, pressure oversampling
	dataToWrite |= (settings.pressOverSample << 0x02) & 0x1C;
	//Last, set mode
	dataToWrite |= (settings.runMode) & 0x03;
	//Load the byte
	writeRegister(BME280_CTRL_MEAS_REG, dataToWrite);

	return readRegister(0xD0);
}

//Strictly resets.  Run .begin() afterwards
void BME280::reset( void )
{
	writeRegister(BME280_RST_REG, 0xB6);

}

//****************************************************************************//
//
//  Pressure Section
//
//****************************************************************************//
float BME280::readFloatPressure( void )
{

	// Returns pressure in Pa as unsigned 32 bit integer in Q24.8 format (24 integer bits and 8 fractional bits).
	// Output value of “24674867” represents 24674867/256 = 96386.2 Pa = 963.862 hPa
	int32_t adc_P = ((uint32_t)readRegister(BME280_PRESSURE_MSB_REG) << 12) | ((uint32_t)readRegister(BME280_PRESSURE_LSB_REG) << 4) | ((readRegister(BME280_PRESSURE_XLSB_REG) >> 4) & 0x0F);

	int64_t var1, var2, p_acc;
	var1 = ((int64_t)t_fine) - 128000;
	var2 = var1 * var1 * (int64_t)calibration.dig_P6;
	var2 = var2 + ((var1 * (int64_t)calibration.dig_P5)<<17);
	var2 = var2 + (((int64_t)calibration.dig_P4)<<35);
	var1 = ((var1 * var1 * (int64_t)calibration.dig_P3)>>8) + ((var1 * (int64_t)calibration.dig_P2)<<12);
	var1 = (((((int64_t)1)<<47)+var1))*((int64_t)calibration.dig_P1)>>33;
	if (var1 == 0)
	{
		return 0; // avoid exception caused by division by zero
	}
	p_acc = 1048576 - adc_P;
	p_acc = (((p_acc<<31) - var2)*3125)/var1;
	var1 = (((int64_t)calibration.dig_P9) * (p_acc>>13) * (p_acc>>13)) >> 25;
	var2 = (((int64_t)calibration.dig_P8) * p_acc) >> 19;
	p_acc = ((p_acc + var1 + var2) >> 8) + (((int64_t)calibration.dig_P7)<<4);

	p_acc = p_acc >> 8; // /256
	return (float)p_acc;

}

float BME280::readFloatAltitudeMeters( void )
{
	float heightOutput = 0;

	heightOutput = ((float)-45846.2)*(pow(((float)readFloatPressure()/(float)101325), 0.190263) - (float)1);
	return heightOutput;

}

float BME280::readFloatAltitudeFeet( void )
{
	float heightOutput = 0;

	heightOutput = readFloatAltitudeMeters() * 3.28084;
	return heightOutput;

}

//****************************************************************************//
//
//  Humidity Section
//
//****************************************************************************//
float BME280::readFloatHumidity( void )
{

	// Returns humidity in %RH as unsigned 32 bit integer in Q22. 10 format (22 integer and 10 fractional bits).
	// Output value of “47445” represents 47445/1024 = 46. 333 %RH
	int32_t adc_H = ((uint32_t)readRegister(BME280_HUMIDITY_MSB_REG) << 8) | ((uint32_t)readRegister(BME280_HUMIDITY_LSB_REG));

	int32_t var1;
	var1 = (t_fine - ((int32_t)76800));
	var1 = (((((adc_H << 14) - (((int32_t)calibration.dig_H4) << 20) - (((int32_t)calibration.dig_H5) * var1)) +
	((int32_t)16384)) >> 15) * (((((((var1 * ((int32_t)calibration.dig_H6)) >> 10) * (((var1 * ((int32_t)calibration.dig_H3)) >> 11) + ((int32_t)32768))) >> 10) + ((int32_t)2097152)) *
	((int32_t)calibration.dig_H2) + 8192) >> 14));
	var1 = (var1 - (((((var1 >> 15) * (var1 >> 15)) >> 7) * ((int32_t)calibration.dig_H1)) >> 4));
	var1 = (var1 < 0 ? 0 : var1);
	var1 = (var1 > 419430400 ? 419430400 : var1);

	return (float)((var1>>12) >> 10);

}



//****************************************************************************//
//
//  Temperature Section
//
//****************************************************************************//

float BME280::readTempC( void )
{
	// Returns temperature in DegC, resolution is 0.01 DegC. Output value of “5123” equals 51.23 DegC.
	// t_fine carries fine temperature as global value

	//get the reading (adc_T);
	int32_t adc_T = ((uint32_t)readRegister(BME280_TEMPERATURE_MSB_REG) << 12) | ((uint32_t)readRegister(BME280_TEMPERATURE_LSB_REG) << 4) | ((readRegister(BME280_TEMPERATURE_XLSB_REG) >> 4) & 0x0F);

	//By datasheet, calibrate
	int64_t var1, var2;

	var1 = ((((adc_T>>3) - ((int32_t)calibration.dig_T1<<1))) * ((int32_t)calibration.dig_T2)) >> 11;
	var2 = (((((adc_T>>4) - ((int32_t)calibration.dig_T1)) * ((adc_T>>4) - ((int32_t)calibration.dig_T1))) >> 12) *
	((int32_t)calibration.dig_T3)) >> 14;
	t_fine = var1 + var2;
	float output = (t_fine * 5 + 128) >> 8;

	output = output / 100;

	return output;
}

float BME280::readTempF( void )
{
	float output = readTempC();
	output = (output * 9) / 5 + 32;

	return output;
}

//****************************************************************************//
//
//  Utility
//
//****************************************************************************//
void BME280::readRegisterRegion(uint8_t *outputPointer , uint8_t offset, uint8_t length)
{
	//define pointer that will point to the external space
	uint8_t i = 0;
	char c = 0;

	switch (settings.commInterface)
	{

	case I2C_MODE:
		Wire.beginTransmission(settings.I2CAddress);
		Wire.write(offset);
		Wire.endTransmission();

		// request bytes from slave device
		Wire.requestFrom(settings.I2CAddress, length);
		while ( (Wire.available()) && (i < length))  // slave may send less than requested
		{
			c = Wire.read(); // receive a byte as character
			*outputPointer = c;
			outputPointer++;
			i++;
		}
		break;

	case SPI_MODE:
		// take the chip select low to select the device:
		digitalWrite(settings.chipSelectPin, LOW);
		// send the device the register you want to read:
		SPI.transfer(offset | 0x80);  //Ored with "read request" bit
		while ( i < length ) // slave may send less than requested
		{
			c = SPI.transfer(0x00); // receive a byte as character
			*outputPointer = c;
			outputPointer++;
			i++;
		}
		// take the chip select high to de-select:
		digitalWrite(settings.chipSelectPin, HIGH);
		break;

	default:
		break;
	}

}

uint8_t BME280::readRegister(uint8_t offset)
{
	//Return value
	uint8_t result;
	uint8_t numBytes = 1;
	switch (settings.commInterface) {

	case I2C_MODE:
		Wire.beginTransmission(settings.I2CAddress);
		Wire.write(offset);
		Wire.endTransmission();

		Wire.requestFrom(settings.I2CAddress, numBytes);
		while ( Wire.available() ) // slave may send less than requested
		{
			result = Wire.read(); // receive a byte as a proper uint8_t
		}
		break;

	case SPI_MODE:
		// take the chip select low to select the device:
		digitalWrite(settings.chipSelectPin, LOW);
		// send the device the register you want to read:
		SPI.transfer(offset | 0x80);  //Ored with "read request" bit
		// send a value of 0 to read the first byte returned:
		result = SPI.transfer(0x00);
		// take the chip select high to de-select:
		digitalWrite(settings.chipSelectPin, HIGH);
		break;

	default:
		break;
	}
	return result;
}

int16_t BME280::readRegisterInt16( uint8_t offset )
{
	uint8_t myBuffer[2];
	readRegisterRegion(myBuffer, offset, 2);  //Does memory transfer
	int16_t output = (int16_t)myBuffer[0] | int16_t(myBuffer[1] << 8);

	return output;
}

void BME280::writeRegister(uint8_t offset, uint8_t dataToWrite)
{
	switch (settings.commInterface)
	{
	case I2C_MODE:
		//Write the byte
		Wire.beginTransmission(settings.I2CAddress);
		Wire.write(offset);
		Wire.write(dataToWrite);
		Wire.endTransmission();
		break;

	case SPI_MODE:
		// take the chip select low to select the device:
		digitalWrite(settings.chipSelectPin, LOW);
		// send the device the register you want to read:
		SPI.transfer(offset & 0x7F);
		// send a value of 0 to read the first byte returned:
		SPI.transfer(dataToWrite);
		// decrement the number of bytes left to read:
		// take the chip select high to de-select:
		digitalWrite(settings.chipSelectPin, HIGH);
		break;

	default:
		break;
	}
}