Diff: Barometer.cpp

Revision:

3:ee90a9ada112

Parent:

2:3898208e02da

Child:

4:e759b8c756da

--- a/Barometer.cpp	Wed Jan 14 17:57:11 2015 +0000
+++ b/Barometer.cpp	Wed Jan 21 10:34:45 2015 +0000
@@ -37,8 +37,8 @@
     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);
+        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 {
@@ -58,7 +58,7 @@
     8.7, // 2x
     13.3, // 4x
     22.5, // 8x
-    43.2, // 16x
+    50, // 16x
 };
 
 enum Filtering {
@@ -85,30 +85,49 @@
               0x01 /* force reading mode */);
 
     // wait until it's done
-    wait_ms(waitTime_ms[psrovr]); // XXX: what does this mean for BLE?
+    //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
+// These typedefs are for Bosch's conversion algorithms below
+typedef uint32_t BMP280_U32_t;
 typedef int32_t BMP280_S32_t;
+typedef int64_t BMP280_S64_t;
+
+// 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
 static BMP280_S32_t t_fine;
-static double bmp280_val_to_Pa(BMP280_S32_t adc_P)
+
+double bmp280_val_to_temp(BMP280_S32_t adc_T)
 {
-    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) {
+    BMP280_S32_t var1, var2, T;
+    var1 = ((((adc_T>>3) - ((BMP280_S32_t)dig_T1<<1))) * ((BMP280_S32_t)dig_T2)) >> 11;
+    var2 = (((((adc_T>>4) - ((BMP280_S32_t)dig_T1)) * ((adc_T>>4) - ((BMP280_S32_t)dig_T1))) >> 12) *
+            ((BMP280_S32_t)dig_T3)) >> 14;
+    t_fine = var1 + var2;
+    T =(t_fine*5+128)>>8;
+    return T / 100.0;
+}
+
+// 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
+double bmp280_val_to_pa(BMP280_S32_t adc_P)
+{
+    BMP280_S64_t var1, var2, p;
+    var1 = ((BMP280_S64_t)t_fine) - 128000;
+    var2 = var1 * var1 * (BMP280_S64_t)dig_P6;
+    var2 = var2 + ((var1*(BMP280_S64_t)dig_P5)<<17);
+    var2 = var2 + (((BMP280_S64_t)dig_P4)<<35);
+    var1 = ((var1 * var1 * (BMP280_S64_t)dig_P3)>>8) + ((var1 * (BMP280_S64_t)dig_P2)<<12);
+    var1 = (((((BMP280_S64_t)1)<<47)+var1))*((BMP280_S64_t)dig_P1)>>33;
+    if (var1 == 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;
+    p = 1048576-adc_P;
+    p = (((p<<31)-var2)*3125)/var1;
+    var1 = (((BMP280_S64_t)dig_P9) * (p>>13) * (p>>13)) >> 25;
+    var2 = (((BMP280_S64_t)dig_P8) * p) >> 19;
+    p = ((p + var1 + var2) >> 8) + (((BMP280_S64_t)dig_P7)<<4);
+    return ((BMP280_U32_t)p) / 256.0;
 }
 
 Barometer::Barometer(I2C &i2c) : I2CPeripheral(i2c, 0xEC /* address */)
@@ -131,15 +150,27 @@
     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;
+    const uint32_t val = (msb << 12) | (lsb << 4) | ((xlsb & 0xF0) >> 4);
+    return bmp280_val_to_pa(val) / 100.0;
 }
 
-double Barometer::getHeightFromPressure(const double p) {
-    const double R = 287.05; //general gas constant
+double Barometer::getTemperature()
+{
+    takeMeasurement(kOversample_1x, kSkip);
+    const uint8_t msb = read_reg(0xFA);
+    const uint8_t lsb = read_reg(0xFB);
+    const uint8_t xlsb = read_reg(0xFC);
+    const uint32_t val = (msb << 12) | (lsb << 4) | ((xlsb & 0xF0) >> 4);
+    return bmp280_val_to_temp(val);
+}
+
+double Barometer::getAltitude()
+{
+    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 T = 297.6; // supposed to be average temperature between p and p0
     const double p0 = 1000.0; // hPa sea level
+    const double p = getPressure();
     const double h = (R / g) * T * log(p0 / p);
     return h;
 }
\ No newline at end of file