Diff: BMP180.cpp

Revision:

0:9a0671b6009f

Child:

1:072073c79cfd

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/BMP180.cpp	Sat Mar 08 21:42:40 2014 +0000
@@ -0,0 +1,221 @@
+/*
+  @file BMP180.cpp
+
+  @brief Barometric Pressure and Temperature Sensor BMP180 Breakout I2C Library
+
+  @Author spiridion (http://mailme.spiridion.net)
+
+  Tested on LPC1768 and FRDM-KL25Z
+
+  Copyright (c) 2014 spiridion
+  Released under the MIT License (see http://mbed.org/license/mit)
+
+  Documentation regarding the BMP180 can be found here:
+                     ...............
+*/
+
+#include "BMP180.h"
+#include "mbed.h"
+
+// Uncomment to test the documentation algorithm against the documentation example 
+// Result should be 699.64 hPa and 15°C
+// #define BMP180_TEST_FORMULA 
+
+BMP180::BMP180(PinName sda, PinName scl, int address)
+   : m_i2c(sda,scl), m_addr(address)
+{
+    Initialize();
+}
+
+BMP180::BMP180(I2C& i2c, int address)
+   : m_i2c(i2c), m_addr(address)
+{
+    Initialize();
+}
+
+int  BMP180::Initialize(float altitude, int overSamplingSetting)
+{
+    char data[22];
+    int errors = 0;
+        
+    m_altitude = altitude;
+    m_oss = overSamplingSetting; 
+
+    m_temperature = UNSET_BMP180_TEMPERATURE_VALUE;
+    m_pressure = UNSET_BMP180_PRESSURE_VALUE;  
+    
+    // read calibration data
+    data[0]=0xAA;
+    errors = m_i2c.write(m_addr, data, 1);  // set the eeprom pointer position to 0xAA
+    errors += m_i2c.read(m_addr, data, 22); // read 11 x 16 bits at this position 
+    wait_ms(10);
+    
+    // store calibration data for further calculus  
+    ac1 = data[0]  << 8 | data[1];
+    ac2 = data[2]  << 8 | data[3];
+    ac3 = data[4]  << 8 | data[5];
+    ac4 = data[6]  << 8 | data[7];
+    ac5 = data[8]  << 8 | data[9];
+    ac6 = data[10] << 8 | data[11];
+    b1  = data[12] << 8 | data[13];
+    b2  = data[14] << 8 | data[15];
+    mb  = data[16] << 8 | data[17];
+    mc  = data[18] << 8 | data[19];
+    md  = data[20] << 8 | data[21];
+
+#ifdef BMP180_TEST_FORMULA
+    ac1 = 408;
+    ac2 = -72;
+    ac3 = -14383;
+    ac4 = 32741;
+    ac5 = 32757;
+    ac6 = 23153;
+    b1 = 6190;
+    b2 = 4;
+    mb = -32768;
+    mc = -8711;
+    md = 2868;
+    m_oss = 0;
+    errors = 0;
+#endif // #ifdef BMP180_TEST_FORMULA
+
+    return errors? 0 : 1;
+}
+
+int BMP180::ReadData(float* pTemperature, float* pPressure)
+{
+    long t, p;
+
+    if (!ReadRawTemperature(&t) || !ReadRawPressure(&p))
+    {
+        m_temperature = UNSET_BMP180_TEMPERATURE_VALUE;
+        m_pressure = UNSET_BMP180_PRESSURE_VALUE;  
+        return 0;
+    }
+
+    m_temperature = TrueTemperature(t);
+    m_pressure = TruePressure(p);
+
+    if (pPressure)
+        *pPressure = m_pressure;
+    if (pTemperature)
+        *pTemperature = m_temperature;
+
+    return 1;
+}
+
+int BMP180::ReadRawTemperature(long* pUt)
+{
+    int errors = 0;
+    char data[2];
+    
+    // request temperature measurement
+    data[0] = 0xF4;
+    data[1] = 0x2E;
+    errors = m_i2c.write(m_addr, data, 2); // write 0XF2 into reg 0XF4
+
+    wait_ms(4.5F);
+
+    // read raw temperature data
+    data[0] = 0xF6;
+    errors += m_i2c.write(m_addr, data, 2); // set eeprom pointer position to 0XF6
+    errors += m_i2c.read(m_addr, data, 2);  // get 16 bits at this position 
+    
+#ifdef BMP180_TEST_FORMULA
+    errors = 0;
+#endif // #ifdef BMP180_TEST_FORMULA
+
+    if (errors)
+        return 0;
+    else
+        *pUt = data[0] << 8 | data[1];
+
+#ifdef BMP180_TEST_FORMULA
+    *pUt = 27898;
+#endif // #ifdef BMP180_TEST_FORMULA
+    
+    return 1;
+}
+
+int BMP180::ReadRawPressure(long* pUp)
+{
+    int errors = 0;
+    char data[2];
+    
+    // request pressure measurement
+    data[0] = 0xF4;
+    data[1] = 0x34 + (m_oss << 6);
+    errors = m_i2c.write(m_addr, data, 2); // write 0x34 + (m_oss << 6) into reg 0XF4
+
+    switch (m_oss)
+    {
+        case BMP180_OSS_ULTRA_LOW_POWER:        wait_ms(4.5); break;
+        case BMP180_OSS_NORMAL:                 wait_ms(7.5); break;
+        case BMP180_OSS_HIGH_RESOLUTION:        wait_ms(13.5); break;
+        case BMP180_OSS_ULTRA_HIGH_RESOLUTION:  wait_ms(25.5); break;
+    }
+
+    // read raw pressure data
+    data[0] = 0xF6;
+    errors += m_i2c.write(m_addr, data, 1); // set eeprom pointer position to 0XF6
+    errors += m_i2c.read(m_addr, data, 2);  // get 16 bits at this position     
+    
+#ifdef BMP180_TEST_FORMULA
+    errors = 0;
+#endif // #ifdef BMP180_TEST_FORMULA
+
+    if (errors)
+        return 0;
+    else
+        *pUp = (data[0] << 16 | data[1] << 8) >> (8 - m_oss);
+#ifdef BMP180_TEST_FORMULA
+        *pUp = 23843;
+#endif // #ifdef BMP180_TEST_FORMULA
+
+    return 1;
+}
+
+float BMP180::TrueTemperature(long ut)
+{
+    long t;
+    
+    // straight out from the documentation
+    x1 = ((ut - ac6) * ac5) >> 15;
+    x2 = ((long)mc << 11) / (x1 + md);
+    b5 = x1 + x2;
+    t = (b5 + 8) >> 4;
+
+    // convert to celcius
+    return t / 10.F;
+}
+
+float BMP180::TruePressure(long up)
+{
+    long p;
+    
+    // straight out from the documentation
+    b6 = b5 - 4000;
+    x1 = (b2 * (b6 * b6 >> 12)) >> 11;
+    x2 = ac2 * b6 >> 11;
+    x3 = x1 + x2;
+    b3 = (((ac1 * 4 + x3) << m_oss) + 2) >> 2;
+    x1 = (ac3 * b6) >> 13;
+    x2 = (b1 * ((b6 * b6) >> 12)) >> 16;
+    x3 = ((x1 + x2) + 2) >> 2;
+    b4 = ac4 * (unsigned long)(x3 + 32768) >> 15;
+    b7 = ((unsigned long)up - b3)* (50000 >> m_oss);
+    if (b7 < 0x80000000)
+        p = (b7 << 1) / b4;
+    else
+        p = (b7 / b4) << 1;
+    x1 = (p >> 8) * (p >> 8);
+    x1 = (x1 * 3038) >> 16;
+    x2 = (-7357 * p) >> 16;
+    p = p + ((x1 + x2 + 3791) >> 4);
+
+    // convert to hPa and, if altitude has been initialized, to sea level pressure  
+    if (m_altitude == 0.F)
+        return p / 100.F;
+    else
+        return  p / (100.F * pow((1.F - m_altitude / 44330.0L), 5.255L)); 
+}
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