Library for getting temperature and pressure values from Bosch BMP180 barometer.
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Diff: BMP180.cpp
- Revision:
- 4:1eec283ff5e7
- Parent:
- 3:0e92710a46f9
--- a/BMP180.cpp Sat Mar 14 12:57:44 2015 +0000 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,245 +0,0 @@ -/** -@file BMP180.cpp - -@brief Member functions implementations - -*/ -#include "mbed.h" -#include "BMP180.h" - -BMP180::BMP180(PinName sdaPin, PinName sclPin) -{ - i2c = new I2C(sdaPin,sclPin); // create new I2C instance and initialise - i2c->frequency(400000); // I2C Fast Mode - 400kHz - leds = new BusOut(LED4,LED3,LED2,LED1); -} - -Measurement BMP180::readValues() -{ - // algorithm for taking measurement is taken from datasheet - int32_t UT = readUncompensatedTemperatureValue(); - int32_t UP = readUncompensatedPressureValue(); - // once you have the uncompensated T and P, you can calculate the true T and P - // using the equations from the datasheet - int32_t T = calcTrueTemperature(UT); - int32_t P = calcTruePressure(UP); - - Measurement measurement; - measurement.temperature = T*0.1; // scaled by 0.1 C - measurement.pressure = P*0.01; // Put pressure in mb - - return measurement; -} - -int32_t BMP180::readUncompensatedTemperatureValue() -{ - // from algorithm in datasheet - p15 - sendByteToRegister(0x2E,0xF4); - wait_ms(5); // 4.5 ms delay for OSS = 1 - char MSB = readByteFromRegister(0xF6); - char LSB = readByteFromRegister(0xF7); - // combine in 16-bit value - int UT = (MSB << 8) | LSB; -#ifdef DEBUG - UT = 27898; // test data from datasheet - printf("****DEBUG MODE****\nUT = %d\n",UT); -#endif - return UT; -} - -int32_t BMP180::readUncompensatedPressureValue() -{ - // from datasheet - char byte = 0x34 + (oss << 6); - sendByteToRegister(byte,0xF4); - wait_ms(8); // 7.5 ms delay for OSS = 1 - - char MSB = readByteFromRegister(0xF6); - char LSB = readByteFromRegister(0xF7); - char XLSB = readByteFromRegister(0xF7); - int UP = (MSB << 16 | LSB << 8 | XLSB) >> (8 - oss); - -#ifdef DEBUG - UP = 23843; // test data from datasheet - printf("UP = %d\n",UP); -#endif - return UP; -} - -int32_t BMP180::calcTrueTemperature(int32_t UT) -{ - // equations from data sheet - X1 = ((UT - calibration.AC6)*calibration.AC5) >> 15; - X2 = (calibration.MC << 11) / (X1 + calibration.MD); - B5 = X1 + X2; - int32_t T = (B5 + 8) >> 4; -#ifdef DEBUG - printf("****\nX1=%d\nX2=%d\nB5=%d\nT=%d\n",X1,X2,B5,T); -#endif - return T; -} - -int32_t BMP180::calcTruePressure(int32_t UP) -{ - // equations from data sheet - B6 = B5 - 4000; - X1 = (calibration.B2 * ((B6*B6) >> 12))>>11; - X2 = (calibration.AC2*B6)>>11; - X3 = X1 + X2; - B3 = (((calibration.AC1*4 + X3) << oss)+2)/4; -#ifdef DEBUG - printf("*****\nB6=%d\nX1=%d\nX2=%d\nX3=%d\nB3=%d\n",B6,X1,X2,X3,B3); -#endif - X1 = (calibration.AC3*B6)>>13; - X2 = (calibration.B1*((B6*B6)>>12))>>16; - X3 = ((X1+X2)+2)/4; - B4 = (calibration.AC4*(uint32_t)(X3+32768))>>15; -#ifdef DEBUG - printf("X1=%d\nX2=%d\nX3=%d\nB4=%u\n",X1,X2,X3,B4); -#endif - B7 = ((uint32_t)UP - B3)*(50000>>oss); -#ifdef DEBUG - printf("B7=%u\n",B7); -#endif - int32_t P; - if (B7 < 0x80000000) - P = (B7*2)/B4; - else - P = (B7/B4)*2; -#ifdef DEBUG - printf("P=%d\n",P); -#endif - X1 = (P>>8)*(P>>8); -#ifdef DEBUG - printf("X1=%d\n",X1); -#endif - X1 = (X1*3038)>>16; -#ifdef DEBUG - printf("X1=%d\n",X1); -#endif - X2 = (-7357*P)>>16; -#ifdef DEBUG - printf("X2=%d\n",X2); -#endif - P = P + (X1+X2+3791)/16; -#ifdef DEBUG - printf("P=%d\n",P); -#endif - - return P; - -} - -// configure the barometer -void BMP180::init() -{ - i2c->frequency(400000); // set Fast Mode I2C frequency - - char data = readByteFromRegister(ID_REG); // Section 4 - datasheet - if (data != 0x55) { // if correct ID not found, hang and flash error message - error(); - } - - readCalibrationData(); - - oss = 1; // standard power oversampling setting - -#ifdef DEBUG - oss = 0; // used when testing data sheet example -#endif - - -} - -// Reads factory calibrated data -void BMP180::readCalibrationData() -{ - - char eeprom[22]; - - readBytesFromRegister(EEPROM_REG_ADD,22,eeprom); - // store calibration data in structure - calibration.AC1 = (int16_t) (eeprom[0] << 8) | eeprom[1]; - calibration.AC2 = (int16_t) (eeprom[2] << 8) | eeprom[3]; - calibration.AC3 = (int16_t) (eeprom[4] << 8) | eeprom[5]; - calibration.AC4 = (uint16_t) (eeprom[6] << 8) | eeprom[7]; - calibration.AC5 = (uint16_t) (eeprom[8] << 8) | eeprom[9]; - calibration.AC6 = (uint16_t) (eeprom[10] << 8) | eeprom[11]; - calibration.B1 = (int16_t) (eeprom[12] << 8) | eeprom[13]; - calibration.B2 = (int16_t) (eeprom[14] << 8) | eeprom[15]; - calibration.MB = (int16_t) (eeprom[16] << 8) | eeprom[17]; - calibration.MC = (int16_t) (eeprom[18] << 8) | eeprom[19]; - calibration.MD = (int16_t) (eeprom[20] << 8) | eeprom[21]; - - // test data from data sheet -#ifdef DEBUG - calibration.AC1 = 408; - calibration.AC2 = -72; - calibration.AC3 = -14383; - calibration.AC4 = 32741; - calibration.AC5 = 32757; - calibration.AC6 = 23153; - calibration.B1 = 6190; - calibration.B2 = 4; - calibration.MB = -32768; - calibration.MC = -8711; - calibration.MD = 2868; - printf("****EXAMPLE CALIBRATION DATA****\n"); - printf("AC1=%d\nAC2=%d\nAC3=%d\nAC4=%u\nAC5=%u\nAC6=%u\nB1=%d\nB2=%d\nMB=%d\nMC=%d\nMD=%d\n", - calibration.AC1,calibration.AC2,calibration.AC3,calibration.AC4,calibration.AC5,calibration.AC6, - calibration.B1,calibration.B2,calibration.MB,calibration.MC,calibration.MD); -#endif -} - - -// reads a byte from a specific register -char BMP180::readByteFromRegister(char reg) -{ - int nack = i2c->write(BMP180_W_ADDRESS,®,1,true); // send the register address to the slave - if (nack) - error(); // if we don't receive acknowledgement, flash error message - - char rx; - nack = i2c->read(BMP180_W_ADDRESS,&rx,1); // read a byte from the register and store in buffer - if (nack) - error(); // if we don't receive acknowledgement, flash error message - - return rx; -} - -// reads a series of bytes, starting from a specific register -void BMP180::readBytesFromRegister(char reg,int numberOfBytes,char bytes[]) -{ - int nack = i2c->write(BMP180_W_ADDRESS,®,1,true); // send the slave write address and the configuration register address - - if (nack) - error(); // if we don't receive acknowledgement, flash error message - - nack = i2c->read(BMP180_W_ADDRESS,bytes,numberOfBytes); // read bytes - if (nack) - error(); // if we don't receive acknowledgement, flash error message - -} - -// sends a byte to a specific register -void BMP180::sendByteToRegister(char byte,char reg) -{ - char data[2]; - data[0] = reg; - data[1] = byte; - // send the register address, followed by the data - int nack = i2c->write(BMP180_W_ADDRESS,data,2); - if (nack) - error(); // if we don't receive acknowledgement, flash error message - -} - -void BMP180::error() -{ - while(1) { - leds->write(15); - wait(0.1); - leds->write(0); - wait(0.1); - } -} \ No newline at end of file