Diff: BMP180.h

Revision:

3:b6d2c5195055

diff -r 654ee4b3950f -r b6d2c5195055 BMP180.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/BMP180.h	Thu Nov 12 22:42:05 2015 +0000
@@ -0,0 +1,155 @@
+#ifndef BMP180_H
+#define BMP180_H
+ 
+#include "mbed.h"
+
+#define BMP180_ADDRESS          0x77<<1 // I2C address of BMP180, eight bit address on mbed
+#define BMP180_WHO_AM_I         0xD0    // WHO_AM_I id of BMP180, should return 0x55
+#define BMP180_RESET            0xE0
+#define BMP180_CONTROL          0xF4
+#define BMP180_OUT_MSB          0xF6
+#define BMP180_OUT_LSB          0xF7
+#define BMP180_OUT_XLSB         0xF8
+
+// Set initial input parameters
+
+enum OSS {  // BMP-085 sampling rate
+  OSS_0 = 0,  // 4.5 ms conversion time
+  OSS_1,      // 7.5
+  OSS_2,      // 13.5
+  OSS_3       // 25.5
+};
+
+uint8_t OSS = OSS_3;           // maximum pressure resolution
+
+//Set up I2C, (SDA,SCL)
+I2C i2c(I2C_SDA, I2C_SCL);
+    
+// These are constants used to calculate the temperature and pressure from the BMP-180 sensor
+int16_t ac1, ac2, ac3, b1, b2, mb, mc, md, b5;  
+uint16_t ac4, ac5, ac6;
+
+class BMP180 {
+ 
+    protected:
+ 
+    public:
+  //===================================================================================================================
+//====== Set of useful function to access pressure and temperature data
+//===================================================================================================================
+
+    void writeByte(uint8_t address, uint8_t subAddress, uint8_t data)
+{
+   char data_write[2];
+   data_write[0] = subAddress;
+   data_write[1] = data;
+   i2c.write(address, data_write, 2, 0);
+}
+
+    char readByte(uint8_t address, uint8_t subAddress)
+{
+    char data[1]; // `data` will store the register data     
+    char data_write[1];
+    data_write[0] = subAddress;
+    i2c.write(address, data_write, 1, 1); // no stop
+    i2c.read(address, data, 1, 0); 
+    return data[0]; 
+}
+
+    void readBytes(uint8_t address, uint8_t subAddress, uint8_t count, uint8_t * dest)
+{     
+    char data[14];
+    char data_write[1];
+    data_write[0] = subAddress;
+    i2c.write(address, data_write, 1, 1); // no stop
+    i2c.read(address, data, count, 0); 
+    for(int ii = 0; ii < count; ii++) {
+     dest[ii] = data[ii];
+    }
+} 
+ 
+
+// Stores all of the BMP180's calibration values into global variables
+// Calibration values are required to calculate temp and pressure
+// This function should be called at the beginning of the program
+// These BMP-180 functions were adapted from Jim Lindblom of SparkFun Electronics
+void BMP180Calibration()
+{
+  ac1 = readByte(BMP180_ADDRESS, 0xAA) << 8 | readByte(BMP180_ADDRESS, 0xAB);
+  ac2 = readByte(BMP180_ADDRESS, 0xAC) << 8 | readByte(BMP180_ADDRESS, 0xAD);
+  ac3 = readByte(BMP180_ADDRESS, 0xAE) << 8 | readByte(BMP180_ADDRESS, 0xAF);
+  ac4 = readByte(BMP180_ADDRESS, 0xB0) << 8 | readByte(BMP180_ADDRESS, 0xB1);
+  ac5 = readByte(BMP180_ADDRESS, 0xB2) << 8 | readByte(BMP180_ADDRESS, 0xB3);
+  ac6 = readByte(BMP180_ADDRESS, 0xB4) << 8 | readByte(BMP180_ADDRESS, 0xB5);
+  b1  = readByte(BMP180_ADDRESS, 0xB6) << 8 | readByte(BMP180_ADDRESS, 0xB7);
+  b2  = readByte(BMP180_ADDRESS, 0xB8) << 8 | readByte(BMP180_ADDRESS, 0xB9);
+  mb  = readByte(BMP180_ADDRESS, 0xBA) << 8 | readByte(BMP180_ADDRESS, 0xBB);
+  mc  = readByte(BMP180_ADDRESS, 0xBC) << 8 | readByte(BMP180_ADDRESS, 0xBD);
+  md  = readByte(BMP180_ADDRESS, 0xBE) << 8 | readByte(BMP180_ADDRESS, 0xBF);
+}
+
+  // Temperature returned will be in units of 0.1 deg C
+  int16_t BMP180GetTemperature()
+  {
+  int16_t ut = 0;
+  writeByte(BMP180_ADDRESS, 0xF4, 0x2E); // start temperature measurement
+  wait(0.005);
+  uint8_t rawData[2] = {0, 0};
+  readBytes(BMP180_ADDRESS, 0xF6, 2, &rawData[0]); // read raw temperature measurement
+  ut = (((int16_t) rawData[0] << 8) | rawData[1]);
+ 
+ long x1, x2;
+  
+  x1 = (((long)ut - (long)ac6)*(long)ac5) >> 15;
+  x2 = ((long)mc << 11)/(x1 + md);
+  b5 = x1 + x2;
+
+  return  ((b5 + 8)>>4);  
+}
+
+// Calculate pressure read calibration values  
+// b5 is also required so BMP180GetTemperature() must be called first.
+// Value returned will be pressure in units of Pa.
+long BMP180GetPressure()
+{
+  long up = 0;
+  writeByte(BMP180_ADDRESS, 0xF4, 0x34 | OSS << 6); // Configure pressure measurement for highest resolution
+  wait((5.0f + 8.0f*3.0f)/1000.0f); // delay 5 ms at lowest resolution, 29 ms at highest
+  uint8_t rawData[3] = {0, 0, 0};
+  readBytes(BMP180_ADDRESS, 0xF6, 3, &rawData[0]); // read raw pressure measurement of 19 bits
+  up = (((long) rawData[0] << 16) | ((long)rawData[1] << 8) | rawData[2]) >> (8 - OSS);
+
+  long x1, x2, x3, b3, b6, p;
+  unsigned long b4, b7;
+  
+  b6 = b5 - 4000;
+  // Calculate B3
+  x1 = (b2 * (b6 * b6)>>12)>>11;
+  x2 = (ac2 * b6)>>11;
+  x3 = x1 + x2;
+  b3 = (((((long)ac1)*4 + x3)<<OSS) + 2)>>2;
+  
+  // Calculate B4
+  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>>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 += (x1 + x2 + 3791)>>4;
+  
+  return p;
+}      
+
+ 
+ 
+  };
+#endif
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