Kris Winer / Mbed 2 deprecated BMP180

Basic program to read temperature and pressure data from BMP-180 altimeter, convert the temperature into Centigrade and Fahrenheit, and average pressure for highest precision. Use pressure to obtain altitude in meters and feet. Display all to four 4-digit eight-segment bubble displays.

Dependencies:   mbed

Dependents:   GloboMet

BMP180.h@0:06dc60296e6e, 2014-07-03 (annotated)

Committer:
onehorse
Date:
Thu Jul 03 20:05:55 2014 +0000
Revision:
0:06dc60296e6e
Initial commit

Who changed what in which revision?

UserRevisionLine numberNew contents of line
onehorse 0:06dc60296e6e 1 #ifndef BMP180_H
onehorse 0:06dc60296e6e 2 #define BMP180_H
onehorse 0:06dc60296e6e 3
onehorse 0:06dc60296e6e 4 #include "mbed.h"
onehorse 0:06dc60296e6e 5
onehorse 0:06dc60296e6e 6 #define BMP180_ADDRESS 0x77<<1 // I2C address of BMP180, eight bit address on mbed
onehorse 0:06dc60296e6e 7 #define BMP180_WHO_AM_I 0xD0 // WHO_AM_I id of BMP180, should return 0x55
onehorse 0:06dc60296e6e 8 #define BMP180_RESET 0xE0
onehorse 0:06dc60296e6e 9 #define BMP180_CONTROL 0xF4
onehorse 0:06dc60296e6e 10 #define BMP180_OUT_MSB 0xF6
onehorse 0:06dc60296e6e 11 #define BMP180_OUT_LSB 0xF7
onehorse 0:06dc60296e6e 12 #define BMP180_OUT_XLSB 0xF8
onehorse 0:06dc60296e6e 13
onehorse 0:06dc60296e6e 14 // Set initial input parameters
onehorse 0:06dc60296e6e 15
onehorse 0:06dc60296e6e 16 enum OSS { // BMP-085 sampling rate
onehorse 0:06dc60296e6e 17 OSS_0 = 0, // 4.5 ms conversion time
onehorse 0:06dc60296e6e 18 OSS_1, // 7.5
onehorse 0:06dc60296e6e 19 OSS_2, // 13.5
onehorse 0:06dc60296e6e 20 OSS_3 // 25.5
onehorse 0:06dc60296e6e 21 };
onehorse 0:06dc60296e6e 22
onehorse 0:06dc60296e6e 23 uint8_t OSS = OSS_3; // maximum pressure resolution
onehorse 0:06dc60296e6e 24
onehorse 0:06dc60296e6e 25 //Set up I2C, (SDA,SCL)
onehorse 0:06dc60296e6e 26 I2C i2c(I2C_SDA, I2C_SCL);
onehorse 0:06dc60296e6e 27
onehorse 0:06dc60296e6e 28 // These are constants used to calculate the temperature and pressure from the BMP-180 sensor
onehorse 0:06dc60296e6e 29 int16_t ac1, ac2, ac3, b1, b2, mb, mc, md, b5;
onehorse 0:06dc60296e6e 30 uint16_t ac4, ac5, ac6;
onehorse 0:06dc60296e6e 31
onehorse 0:06dc60296e6e 32 class BMP180 {
onehorse 0:06dc60296e6e 33
onehorse 0:06dc60296e6e 34 protected:
onehorse 0:06dc60296e6e 35
onehorse 0:06dc60296e6e 36 public:
onehorse 0:06dc60296e6e 37 //===================================================================================================================
onehorse 0:06dc60296e6e 38 //====== Set of useful function to access pressure and temperature data
onehorse 0:06dc60296e6e 39 //===================================================================================================================
onehorse 0:06dc60296e6e 40
onehorse 0:06dc60296e6e 41 void writeByte(uint8_t address, uint8_t subAddress, uint8_t data)
onehorse 0:06dc60296e6e 42 {
onehorse 0:06dc60296e6e 43 char data_write[2];
onehorse 0:06dc60296e6e 44 data_write[0] = subAddress;
onehorse 0:06dc60296e6e 45 data_write[1] = data;
onehorse 0:06dc60296e6e 46 i2c.write(address, data_write, 2, 0);
onehorse 0:06dc60296e6e 47 }
onehorse 0:06dc60296e6e 48
onehorse 0:06dc60296e6e 49 char readByte(uint8_t address, uint8_t subAddress)
onehorse 0:06dc60296e6e 50 {
onehorse 0:06dc60296e6e 51 char data[1]; // `data` will store the register data
onehorse 0:06dc60296e6e 52 char data_write[1];
onehorse 0:06dc60296e6e 53 data_write[0] = subAddress;
onehorse 0:06dc60296e6e 54 i2c.write(address, data_write, 1, 1); // no stop
onehorse 0:06dc60296e6e 55 i2c.read(address, data, 1, 0);
onehorse 0:06dc60296e6e 56 return data[0];
onehorse 0:06dc60296e6e 57 }
onehorse 0:06dc60296e6e 58
onehorse 0:06dc60296e6e 59 void readBytes(uint8_t address, uint8_t subAddress, uint8_t count, uint8_t * dest)
onehorse 0:06dc60296e6e 60 {
onehorse 0:06dc60296e6e 61 char data[14];
onehorse 0:06dc60296e6e 62 char data_write[1];
onehorse 0:06dc60296e6e 63 data_write[0] = subAddress;
onehorse 0:06dc60296e6e 64 i2c.write(address, data_write, 1, 1); // no stop
onehorse 0:06dc60296e6e 65 i2c.read(address, data, count, 0);
onehorse 0:06dc60296e6e 66 for(int ii = 0; ii < count; ii++) {
onehorse 0:06dc60296e6e 67 dest[ii] = data[ii];
onehorse 0:06dc60296e6e 68 }
onehorse 0:06dc60296e6e 69 }
onehorse 0:06dc60296e6e 70
onehorse 0:06dc60296e6e 71
onehorse 0:06dc60296e6e 72 // Stores all of the BMP180's calibration values into global variables
onehorse 0:06dc60296e6e 73 // Calibration values are required to calculate temp and pressure
onehorse 0:06dc60296e6e 74 // This function should be called at the beginning of the program
onehorse 0:06dc60296e6e 75 // These BMP-180 functions were adapted from Jim Lindblom of SparkFun Electronics
onehorse 0:06dc60296e6e 76 void BMP180Calibration()
onehorse 0:06dc60296e6e 77 {
onehorse 0:06dc60296e6e 78 ac1 = readByte(BMP180_ADDRESS, 0xAA) << 8 | readByte(BMP180_ADDRESS, 0xAB);
onehorse 0:06dc60296e6e 79 ac2 = readByte(BMP180_ADDRESS, 0xAC) << 8 | readByte(BMP180_ADDRESS, 0xAD);
onehorse 0:06dc60296e6e 80 ac3 = readByte(BMP180_ADDRESS, 0xAE) << 8 | readByte(BMP180_ADDRESS, 0xAF);
onehorse 0:06dc60296e6e 81 ac4 = readByte(BMP180_ADDRESS, 0xB0) << 8 | readByte(BMP180_ADDRESS, 0xB1);
onehorse 0:06dc60296e6e 82 ac5 = readByte(BMP180_ADDRESS, 0xB2) << 8 | readByte(BMP180_ADDRESS, 0xB3);
onehorse 0:06dc60296e6e 83 ac6 = readByte(BMP180_ADDRESS, 0xB4) << 8 | readByte(BMP180_ADDRESS, 0xB5);
onehorse 0:06dc60296e6e 84 b1 = readByte(BMP180_ADDRESS, 0xB6) << 8 | readByte(BMP180_ADDRESS, 0xB7);
onehorse 0:06dc60296e6e 85 b2 = readByte(BMP180_ADDRESS, 0xB8) << 8 | readByte(BMP180_ADDRESS, 0xB9);
onehorse 0:06dc60296e6e 86 mb = readByte(BMP180_ADDRESS, 0xBA) << 8 | readByte(BMP180_ADDRESS, 0xBB);
onehorse 0:06dc60296e6e 87 mc = readByte(BMP180_ADDRESS, 0xBC) << 8 | readByte(BMP180_ADDRESS, 0xBD);
onehorse 0:06dc60296e6e 88 md = readByte(BMP180_ADDRESS, 0xBE) << 8 | readByte(BMP180_ADDRESS, 0xBF);
onehorse 0:06dc60296e6e 89 }
onehorse 0:06dc60296e6e 90
onehorse 0:06dc60296e6e 91 // Temperature returned will be in units of 0.1 deg C
onehorse 0:06dc60296e6e 92 int16_t BMP180GetTemperature()
onehorse 0:06dc60296e6e 93 {
onehorse 0:06dc60296e6e 94 int16_t ut = 0;
onehorse 0:06dc60296e6e 95 writeByte(BMP180_ADDRESS, 0xF4, 0x2E); // start temperature measurement
onehorse 0:06dc60296e6e 96 wait(0.005);
onehorse 0:06dc60296e6e 97 uint8_t rawData[2] = {0, 0};
onehorse 0:06dc60296e6e 98 readBytes(BMP180_ADDRESS, 0xF6, 2, &rawData[0]); // read raw temperature measurement
onehorse 0:06dc60296e6e 99 ut = (((int16_t) rawData[0] << 8) | rawData[1]);
onehorse 0:06dc60296e6e 100
onehorse 0:06dc60296e6e 101 long x1, x2;
onehorse 0:06dc60296e6e 102
onehorse 0:06dc60296e6e 103 x1 = (((long)ut - (long)ac6)*(long)ac5) >> 15;
onehorse 0:06dc60296e6e 104 x2 = ((long)mc << 11)/(x1 + md);
onehorse 0:06dc60296e6e 105 b5 = x1 + x2;
onehorse 0:06dc60296e6e 106
onehorse 0:06dc60296e6e 107 return ((b5 + 8)>>4);
onehorse 0:06dc60296e6e 108 }
onehorse 0:06dc60296e6e 109
onehorse 0:06dc60296e6e 110 // Calculate pressure read calibration values
onehorse 0:06dc60296e6e 111 // b5 is also required so BMP180GetTemperature() must be called first.
onehorse 0:06dc60296e6e 112 // Value returned will be pressure in units of Pa.
onehorse 0:06dc60296e6e 113 long BMP180GetPressure()
onehorse 0:06dc60296e6e 114 {
onehorse 0:06dc60296e6e 115 long up = 0;
onehorse 0:06dc60296e6e 116 writeByte(BMP180_ADDRESS, 0xF4, 0x34 | OSS << 6); // Configure pressure measurement for highest resolution
onehorse 0:06dc60296e6e 117 wait((5.0f + 8.0f*3.0f)/1000.0f); // delay 5 ms at lowest resolution, 29 ms at highest
onehorse 0:06dc60296e6e 118 uint8_t rawData[3] = {0, 0, 0};
onehorse 0:06dc60296e6e 119 readBytes(BMP180_ADDRESS, 0xF6, 3, &rawData[0]); // read raw pressure measurement of 19 bits
onehorse 0:06dc60296e6e 120 up = (((long) rawData[0] << 16) | ((long)rawData[1] << 8) | rawData[2]) >> (8 - OSS);
onehorse 0:06dc60296e6e 121
onehorse 0:06dc60296e6e 122 long x1, x2, x3, b3, b6, p;
onehorse 0:06dc60296e6e 123 unsigned long b4, b7;
onehorse 0:06dc60296e6e 124
onehorse 0:06dc60296e6e 125 b6 = b5 - 4000;
onehorse 0:06dc60296e6e 126 // Calculate B3
onehorse 0:06dc60296e6e 127 x1 = (b2 * (b6 * b6)>>12)>>11;
onehorse 0:06dc60296e6e 128 x2 = (ac2 * b6)>>11;
onehorse 0:06dc60296e6e 129 x3 = x1 + x2;
onehorse 0:06dc60296e6e 130 b3 = (((((long)ac1)*4 + x3)<<OSS) + 2)>>2;
onehorse 0:06dc60296e6e 131
onehorse 0:06dc60296e6e 132 // Calculate B4
onehorse 0:06dc60296e6e 133 x1 = (ac3 * b6)>>13;
onehorse 0:06dc60296e6e 134 x2 = (b1 * ((b6 * b6)>>12))>>16;
onehorse 0:06dc60296e6e 135 x3 = ((x1 + x2) + 2)>>2;
onehorse 0:06dc60296e6e 136 b4 = (ac4 * (unsigned long)(x3 + 32768))>>15;
onehorse 0:06dc60296e6e 137
onehorse 0:06dc60296e6e 138 b7 = ((unsigned long)(up - b3) * (50000>>OSS));
onehorse 0:06dc60296e6e 139 if (b7 < 0x80000000)
onehorse 0:06dc60296e6e 140 p = (b7<<1)/b4;
onehorse 0:06dc60296e6e 141 else
onehorse 0:06dc60296e6e 142 p = (b7/b4)<<1;
onehorse 0:06dc60296e6e 143
onehorse 0:06dc60296e6e 144 x1 = (p>>8) * (p>>8);
onehorse 0:06dc60296e6e 145 x1 = (x1 * 3038)>>16;
onehorse 0:06dc60296e6e 146 x2 = (-7357 * p)>>16;
onehorse 0:06dc60296e6e 147 p += (x1 + x2 + 3791)>>4;
onehorse 0:06dc60296e6e 148
onehorse 0:06dc60296e6e 149 return p;
onehorse 0:06dc60296e6e 150 }
onehorse 0:06dc60296e6e 151
onehorse 0:06dc60296e6e 152
onehorse 0:06dc60296e6e 153
onehorse 0:06dc60296e6e 154 };
onehorse 0:06dc60296e6e 155 #endif