Implemented first Hangar-Service
Dependencies: CalibrateMagneto QuaternionMath
Fork of SML2 by
Diff: Barometer.cpp
- Revision:
- 2:3898208e02da
- Parent:
- 1:c279bc3af90c
- Child:
- 3:ee90a9ada112
--- a/Barometer.cpp Wed Jan 14 15:44:34 2015 +0000 +++ b/Barometer.cpp Wed Jan 14 17:57:11 2015 +0000 @@ -2,17 +2,144 @@ #define DEBUG "BMP280" #include "Logger.h" -Barometer::Barometer(I2C &i2c) : I2CPeripheral(i2c, 0xEC /* address */) { +// Calibration parameters stored on chip +static uint16_t dig_T1; +static int16_t dig_T2; +static int16_t dig_T3; +static uint16_t dig_P1; +static int16_t dig_P2; +static int16_t dig_P3; +static int16_t dig_P4; +static int16_t dig_P5; +static int16_t dig_P6; +static int16_t dig_P7; +static int16_t dig_P8; +static int16_t dig_P9; + +void Barometer::bmp280_read_cal_reg(const uint8_t reg, char* val) +{ + *val = read_reg(reg); + *(val + 1) = read_reg(reg + 1); +} + +void Barometer::bmp280_read_calibration() +{ + bmp280_read_cal_reg(0x88, (char*)&dig_T1); + bmp280_read_cal_reg(0x8A, (char*)&dig_T2); + bmp280_read_cal_reg(0x8C, (char*)&dig_T3); + bmp280_read_cal_reg(0x8E, (char*)&dig_P1); + bmp280_read_cal_reg(0x90, (char*)&dig_P2); + bmp280_read_cal_reg(0x92, (char*)&dig_P3); + bmp280_read_cal_reg(0x94, (char*)&dig_P4); + bmp280_read_cal_reg(0x96, (char*)&dig_P5); + bmp280_read_cal_reg(0x98, (char*)&dig_P6); + bmp280_read_cal_reg(0x9A, (char*)&dig_P7); + bmp280_read_cal_reg(0x9C, (char*)&dig_P8); + bmp280_read_cal_reg(0x9E, (char*)&dig_P9); + LOG("Calibration parameters: T=[%u, %d, %d] P=[%u, %d, %d, %d, %d, %d, %d, %d, %d]", + dig_T1, dig_T2, dig_T3, + dig_P1, dig_P2, dig_P3, dig_P4, dig_P5, dig_P6, dig_P7, dig_P8, dig_P9); +} + +enum Oversampling { + kSkip = 0, + kOversample_1x = 1, + kOversample_2x = 2, + kOversample_4x = 3, + kOversample_8x = 4, + kOversample_16x = 5, +}; + +// Time taken to read the pressure at a particular oversampling +// cf. page 18 +static float waitTime_ms[] = { + 0, // skip + 6.4, // 1x + 8.7, // 2x + 13.3, // 4x + 22.5, // 8x + 43.2, // 16x +}; + +enum Filtering { + kFilter_None = 0, + kFilter_2x = 1, + kFilter_4x = 2, + kFilter_8x = 3, + kFilter_16x = 4 +}; + +void Barometer::setFilterCoefficient(const uint8_t iir) +{ + write_reg(0xF5, (iir & 0x07) << 1); + INFO("Filter coefficient => %dx", 1 << iir); +} + +void Barometer::takeMeasurement(const uint8_t tmpovr, + const uint8_t psrovr) +{ + // Start a forced measurement + write_reg(0xF4, + ((tmpovr & 0x07) << 5) | + ((psrovr & 0x07) << 2) | + 0x01 /* force reading mode */); + + // wait until it's done + wait_ms(waitTime_ms[psrovr]); // XXX: what does this mean for BLE? +} + +// Returns pressure in Pa as double. Output value of “96386.2” equals 96386.2 Pa = 963.862 hPa +typedef int32_t BMP280_S32_t; +static BMP280_S32_t t_fine; +static double bmp280_val_to_Pa(BMP280_S32_t adc_P) +{ + double var1, var2, p; + var1 = ((double)t_fine/2.0) - 64000.0; + var2 = var1 * var1 * ((double)dig_P6) / 32768.0; + var2 = var2 + var1 * ((double)dig_P5) * 2.0; + var2 = (var2/4.0)+(((double)dig_P4) * 65536.0); + var1 = (((double)dig_P3) * var1 * var1 / 524288.0 + ((double)dig_P2) * var1) / 524288.0; + var1 = (1.0 + var1 / 32768.0)*((double)dig_P1); + if (var1 == 0.0) { + return 0; // avoid exception caused by division by zero + } + p = 1048576.0 - (double)adc_P; + p = (p - (var2 / 4096.0)) * 6250.0 / var1; + var1 = ((double)dig_P9) * p * p / 2147483648.0; + var2 = p * ((double)dig_P8) / 32768.0; + p = p + (var1 + var2 + ((double)dig_P7)) / 16.0; + return p; +} + +Barometer::Barometer(I2C &i2c) : I2CPeripheral(i2c, 0xEC /* address */) +{ write_reg(0xE0, 0xB6); // reset wait_ms(2); // cf. datasheet page 8, t_startup const uint8_t chip_id = read_reg(0xD0); if (chip_id == 0x58) { + bmp280_read_calibration(); + //setFilterCoefficient(kFilter_16x); INFO("Bosch Sensortec BMP280 ready"); } else { WARN("Bosch Sensortec BMP280 not found (chip ID=0x%02x, expected=0x58)", chip_id); } } -float Barometer::getPressure() { - +double Barometer::getPressure() +{ + takeMeasurement(kSkip, kOversample_16x); + const uint8_t msb = read_reg(0xF7); + const uint8_t lsb = read_reg(0xF8); + const uint8_t xlsb = read_reg(0xF9); + const uint32_t val = (msb << 12) | (lsb << 4) | xlsb; + return bmp280_val_to_Pa(val) / 100.0; +} + +double Barometer::getHeightFromPressure(const double p) { + const double R = 287.05; //general gas constant + const double g = 9.80665; // acceleration due to gravity + const double T = 24.0; // temperature + const double p0 = 1000.0; // hPa sea level + const double h = (R / g) * T * log(p0 / p); + return h; } \ No newline at end of file