Diff: IMU/Sensors/Alt/BMP085.cpp

Revision:

4:f62337b907e5

Parent:

0:3e7450f1a938

--- a/IMU/Sensors/Alt/BMP085.cpp	Tue Aug 27 22:18:25 2013 +0000
+++ b/IMU/Sensors/Alt/BMP085.cpp	Thu Aug 29 13:52:30 2013 +0000
@@ -1,57 +1,79 @@
 #include "BMP085.h"
 
-BMP085::BMP085(PinName sda, PinName scl) : I2C_Sensor(sda, scl, BMP085_I2C_ADDRESS)
-{
-    // initialize BMP085 with settings
-    //writeRegister(0xf4, 0x2e); // TODO: was macht das + register in header!
+BMP085::BMP085(PinName sda, PinName scl) : I2C_Sensor(sda, scl, BMP085_I2C_ADDRESS) {
+    // read calibration data from E2PROM, needed for formulas in read function
+    char buffer[22];                                  // 8-Bit pieces of axis data
+    readMultiRegister(BMP085_CAL_AC1, buffer, 22);       // read all calibration registers in one time 22 Byte = 176 Bit
     
+    AC1 = (short) (buffer[0] << 8 | buffer[1]);         // join 8-Bit pieces to 16-bit short integers
+    AC2 = (short) (buffer[2] << 8 | buffer[3]);
+    AC3 = (short) (buffer[4] << 8 | buffer[5]);
+    AC4 = (unsigned short) (buffer[6] << 8 | buffer[7]);      // unsigned !!
+    AC5 = (unsigned short) (buffer[8] << 8 | buffer[9]);
+    AC6 = (unsigned short) (buffer[10] << 8 | buffer[11]);
+    B1 = (short) (buffer[12] << 8 | buffer[13]);
+    B2 = (short) (buffer[14] << 8 | buffer[15]);
+    MB = (short) (buffer[16] << 8 | buffer[17]);
+    MC = (short) (buffer[18] << 8 | buffer[19]);
+    MD = (short) (buffer[20] << 8 | buffer[21]);
+    
+    
+    oss = 0; // set Oversampling of Sensor
+}
+
+void BMP085::readraw() {
 }
 
-/*void BMP085::read() 
-    {
-    long P, UTemp, UPressure, X1, X2, X3, B3, B5, B6;
+void BMP085::read() {
+    unsigned short Uncompensated_Temperature;
+    long P, Uncompensated_Pressure, X1, X2, X3, B3, B5, B6;
     unsigned long B4, B7;
-
-    // TODO: writeRegister(0xf4, 0x2e); ?!!!
-    twi_writechar(BMP085_ADRESS, 0xf4, 0x2e);
-    // Wait at least 4.5ms
-    wait(0.005);
-    UTemp = twi_readshort(BMP085_ADRESS, 0xf6);
+    
+    // read uncompensated Temperature
+    writeRegister(BMP085_CONTROL, READ_TEMPERATURE); // say the sensor we want to read the temperature
+    wait(0.005); // Wait at least 4.5ms (written in data sheet)
+    char buffer[3];  // TODO: nur 2 wenn unten nicht gebraucht                                           // read 16-Bit Temperature (2 registers)
+    readMultiRegister(BMP085_CONTROL_OUTPUT, buffer, 2);        
+    Uncompensated_Temperature =  buffer[0] << 8 | buffer[1];               // join 8-Bit pieces to 16-bit short integer
     
-    X1 = ((UTemp - AC6) * AC5) >> 15;
+    // calculate real Temperature
+    X1 = ((Uncompensated_Temperature - AC6) * AC5) >> 15;
     X2 = (MC << 11) / (X1 + MD);
-    B5 = X1 + X2;
-    Temperature = (float)((B5 + 8) >> 4)/10.0;
-
-    twi_writechar(BMP085_ADRESS, 0xf4, 0x34 + (oss << 6));
-    // Wait at least 4.5ms
-    wait(0.005);
-    UPressure = twi_readlong(BMP085_ADRESS, 0xf6) >> (8 - oss);
-
-    B6 = B5 - 4000;
-    X1 = (B2 * (B6 * B6) >> 12) >> 11;
+    #warning 33 is a calibration value for 3.3 degree shifft of temperature
+    B5 = X1 + X2 - ((33 << 4) - 8); // TODO: I added this term because i think my sensor is about 3.3 degree off which makes a difference in absolute altitude
+    Temperature = (float)((B5 + 8) >> 4)/10.0; // we want temperature in degree with digit after comma
+    
+    // read uncompensated Pressure
+    writeRegister(BMP085_CONTROL, READ_PRESSURE + (oss << 6)); // say the sensor we want to read the pressure
+    wait(0.005); // Wait at least 4.5ms (written in data sheet) TODO: oss fest, times vary and calculation of B3                         
+    readMultiRegister(BMP085_CONTROL_OUTPUT, buffer, 3);                                                    // read 24-Bit Pressure (3 registers)
+    Uncompensated_Pressure = (unsigned int) (buffer[0] << 16 | buffer[1] << 8 | buffer[0]) >> (8 - oss);    // join 8-Bit pieces to 24-bit integer
+    
+    // calculate real Pressure
+    B6 = B5 - 4000;     // B5 is updated by real temperature above
+    X1 = (B2 * ( (B6 * B6) >> 12 )) >> 11;
     X2 = (AC2 * B6) >> 11;
     X3 = X1 + X2;
-    B3 = ((AC1 * 4 + X3) << oss) >> 2;    
+    B3 = (((AC1 * 4 + X3) << oss) + 2) >> 2;
 
     X1 = (AC3 * B6) >> 13;
-    X2 = (B1 * (B6 * B6) >> 12) >> 16;
+    X2 = (B1 * ( (B6 * B6) >> 12) ) >> 16;
     X3 = ((X1 + X2) + 2) >> 2;
-    B4 = AC4 * (X3 + 32768) >> 15;
+    B4 = AC4 * ((unsigned long)X3 + 32768) >> 15;
     
-    B7 = (unsigned long)(UPressure - B3) * (50000 >> oss);
+    B7 = ((unsigned long)Uncompensated_Pressure - B3) * (50000 >> oss);
     
-    if (B7 < 0x80000000) 
-        {
-        P = (2 * B7) / B4;
-        }
+    if (B7 < 0x80000000)
+        P = (B7 * 2) / B4;
     else 
-        {
-        P = 2* (B7 / B4);
-        }
+        P = (B7 / B4) * 2;
+    
     X1 = (P >> 8) * (P >> 8);
     X1 = (X1 * 3038) >> 16;
     X2 = (-7357 * P) >> 16;    
     P = P + ((X1 + X2 + 3791) >> 4);
     Pressure = (float)P / 100.0;
-    }*/
\ No newline at end of file
+    
+    // calculate height out of the pressure
+    Altitude = 44330 * (1.0 - pow((Pressure / 1013.25), 1/5.25588));
+}
\ No newline at end of file