Anyway, I found this guy's C-Code here: http://www.john.geek.nz/2012/08/reading ... pberry-pi/
As he mentions, you have to edit the location of the smbus.h file, and he conveniently provides direct links to those two files for you to wget as well. However, his code does not compile as written, at least it didn't on my setup. GCC complains about NULL not being defined. So, just add '#define NULL 0' toward the top of smbus.c and you should be set.
Below is my version of his code (which was originally derived from a couple other sources as well), which includes calculation and reporting of Altitude and I also changed it to report the temperature and altitude in Imperial measurements. You can easily remove the additional formula on the printf lines back to Metric if you so wish. Anyway, here's my version of his code:
Code: Select all
/*
Raspberry Pi Bosch BMP085 communication code.
By: John Burns (www.john.geek.nz)
Date: 01 August 2012
License: CC BY-SA v3.0 - http://creativecommons.org/licenses/by-sa/3.0/
This is a derivative work based on:
BMP085 Extended Example Code
by: Jim Lindblom
SparkFun Electronics
date: 1/18/11
license: CC BY-SA v3.0 - http://creativecommons.org/licenses/by-sa/3.0/
Source: http://www.sparkfun.com/tutorial/Barometric/BMP085_Example_Code.pde
Compile with: gcc -Wall -o testBMP085 ./smbus.c ./testBMP085.c
Circuit detail:
Using a Spark Fun Barometric Pressure Sensor - BMP085 breakout board
link: https://www.sparkfun.com/products/9694
This comes with pull up resistors already on the i2c lines.
BMP085 pins below are as marked on the Sparkfun BMP085 Breakout board
SDA - P1-03 / IC20-SDA
SCL - P1-05 / IC20_SCL
XCLR - Not Connected
EOC - Not Connected
GND - P1-06 / GND
VCC - P1-01 / 3.3V
Note: Make sure you use P1-01 / 3.3V NOT the 5V pin.
*/
#include <stdio.h>
#include <stdint.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <linux/i2c-dev.h>
#include <linux/i2c.h>
#include <sys/ioctl.h>
#include "smbus.h"
#define BMP085_I2C_ADDRESS 0x77
const unsigned char BMP085_OVERSAMPLING_SETTING = 3;
// Calibration values - These are stored in the BMP085
short int ac1;
short int ac2;
short int ac3;
unsigned short int ac4;
unsigned short int ac5;
unsigned short int ac6;
short int b1;
short int b2;
short int mb;
short int mc;
short int md;
int b5;
unsigned int temperature, pressure, altitude;
// Open a connection to the bmp085
// Returns a file id
int bmp085_i2c_Begin()
{
int fd;
char *fileName = "/dev/i2c-0";
// Open port for reading and writing
if ((fd = open(fileName, O_RDWR)) < 0)
exit(1);
// Set the port options and set the address of the device
if (ioctl(fd, I2C_SLAVE, BMP085_I2C_ADDRESS) < 0) {
close(fd);
exit(1);
}
return fd;
}
// Read two words from the BMP085 and supply it as a 16 bit integer
__s32 bmp085_i2c_Read_Int(int fd, __u8 address)
{
__s32 res = i2c_smbus_read_word_data(fd, address);
if (res < 0) {
close(fd);
exit(1);
}
// Convert result to 16 bits and swap bytes
res = ((res<<8) & 0xFF00) | ((res>>8) & 0xFF);
return res;
}
//Write a byte to the BMP085
void bmp085_i2c_Write_Byte(int fd, __u8 address, __u8 value)
{
if (i2c_smbus_write_byte_data(fd, address, value) < 0) {
close(fd);
exit(1);
}
}
// Read a block of data BMP085
void bmp085_i2c_Read_Block(int fd, __u8 address, __u8 length, __u8 *values)
{
if(i2c_smbus_read_i2c_block_data(fd, address,length,values)<0) {
close(fd);
exit(1);
}
}
void bmp085_Calibration()
{
int fd = bmp085_i2c_Begin();
ac1 = bmp085_i2c_Read_Int(fd,0xAA);
ac2 = bmp085_i2c_Read_Int(fd,0xAC);
ac3 = bmp085_i2c_Read_Int(fd,0xAE);
ac4 = bmp085_i2c_Read_Int(fd,0xB0);
ac5 = bmp085_i2c_Read_Int(fd,0xB2);
ac6 = bmp085_i2c_Read_Int(fd,0xB4);
b1 = bmp085_i2c_Read_Int(fd,0xB6);
b2 = bmp085_i2c_Read_Int(fd,0xB8);
mb = bmp085_i2c_Read_Int(fd,0xBA);
mc = bmp085_i2c_Read_Int(fd,0xBC);
md = bmp085_i2c_Read_Int(fd,0xBE);
close(fd);
}
// Read the uncompensated temperature value
unsigned int bmp085_ReadUT()
{
unsigned int ut = 0;
int fd = bmp085_i2c_Begin();
// Write 0x2E into Register 0xF4
// This requests a temperature reading
bmp085_i2c_Write_Byte(fd,0xF4,0x2E);
// Wait at least 4.5ms
usleep(5000);
// Read the two byte result from address 0xF6
ut = bmp085_i2c_Read_Int(fd,0xF6);
// Close the i2c file
close (fd);
return ut;
}
// Read the uncompensated pressure value
unsigned int bmp085_ReadUP()
{
unsigned int up = 0;
int fd = bmp085_i2c_Begin();
// Write 0x34+(BMP085_OVERSAMPLING_SETTING<<6) into register 0xF4
// Request a pressure reading w/ oversampling setting
bmp085_i2c_Write_Byte(fd,0xF4,0x34 + (BMP085_OVERSAMPLING_SETTING<<6));
// Wait for conversion, delay time dependent on oversampling setting
usleep((2 + (3<<BMP085_OVERSAMPLING_SETTING)) * 1000);
// Read the three byte result from 0xF6
// 0xF6 = MSB, 0xF7 = LSB and 0xF8 = XLSB
__u8 values[3];
bmp085_i2c_Read_Block(fd, 0xF6, 3, values);
up = (((unsigned int) values[0] << 16) | ((unsigned int) values[1] << 8) | (unsigned int) values[2]) >> (8-BMP085_OVERSAMPLING_SETTING);
return up;
}
// Calculate pressure given uncalibrated pressure
// Value returned will be in units of XXXXX
unsigned int bmp085_GetPressure(unsigned int up)
{
int x1, x2, x3, b3, b6, p;
unsigned int b4, b7;
b6 = b5 - 4000;
// Calculate B3
x1 = (b2 * (b6 * b6)>>12)>>11;
x2 = (ac2 * b6)>>11;
x3 = x1 + x2;
b3 = (((((int)ac1)*4 + x3)<<BMP085_OVERSAMPLING_SETTING) + 2)>>2;
// Calculate B4
x1 = (ac3 * b6)>>13;
x2 = (b1 * ((b6 * b6)>>12))>>16;
x3 = ((x1 + x2) + 2)>>2;
b4 = (ac4 * (unsigned int)(x3 + 32768))>>15;
b7 = ((unsigned int)(up - b3) * (50000>>BMP085_OVERSAMPLING_SETTING));
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;
}
// Calculate temperature given uncalibrated temperature
// Value returned will be in units of 0.1 deg C
unsigned int bmp085_GetTemperature(unsigned int ut)
{
int x1, x2;
x1 = (((int)ut - (int)ac6)*(int)ac5) >> 15;
x2 = ((int)mc << 11)/(x1 + md);
b5 = x1 + x2;
unsigned int result = ((b5 + 8)>>4);
return result;
}
// This Altitude part is stolen from some some unknown
// Arduino library. The number divided into pressure for
// float A is derived from the local pressure as explained
// at http://learn.adafruit.com/bmp085/using-the-bmp085.
unsigned int bmp085_Altitude(float pressure)
{
float A = pressure/101794.58;
float B = 1/5.25588;
float C = pow(A,B);
C = 1 - C;
C = C / 0.0000225577;
return C;
}
int main(int argc, char **argv)
{
bmp085_Calibration();
temperature = bmp085_GetTemperature(bmp085_ReadUT());
pressure = bmp085_GetPressure(bmp085_ReadUP());
altitude = bmp085_Altitude(pressure);
printf("Temperature\t%0.1f *F\n", ((double)temperature)/10 * 1.8 + 32);
printf("Pressure\t%0.2f hPa\n", ((double)pressure)/100);
printf("Altitude\t%0.1f Feet\n", ((double)altitude)*3.280839895);
return 0;
}Code: Select all
gcc -Wall -o testBMP085 ./smbus.c ./testBMP085.cCode: Select all
./testBMP085
Temperature 72.3 *F
Pressure 974.60 hPa
Altitude 1197.5 Feet