bmp180.c
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/*
* Copyright (C) 2016 Inria
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup drivers_bmp180
* @{
*
* @file
* @brief Device driver implementation for the BMP180/BMP085 temperature and pressure sensor.
*
* @author Alexandre Abadie <alexandre.abadie@inria.fr>
*
* @}
*/
#include <math.h>
#include "log.h"
#include "bmp180.h"
#include "bmp180_internals.h"
#include "bmp180_params.h"
#include "periph/i2c.h"
#include "xtimer.h"
#define ENABLE_DEBUG (0)
#include "debug.h"
/* Internal function prototypes */
static int _read_ut(bmp180_t *dev, int32_t *ut);
static int _read_up(bmp180_t *dev, int32_t *up);
static int _compute_b5(bmp180_t *dev, int32_t ut, int32_t *b5);
/*---------------------------------------------------------------------------*
* BMP180 Core API *
*---------------------------------------------------------------------------*/
int bmp180_init(bmp180_t *dev, i2c_t i2c, uint8_t mode)
{
dev->i2c_dev = i2c;
/* Clamp oversampling mode */
if (mode > BMP180_ULTRAHIGHRES) {
mode = BMP180_ULTRAHIGHRES;
}
/* Setting oversampling mode */
dev->oversampling = mode;
/* Initialize I2C interface */
if (i2c_init_master(dev->i2c_dev, I2C_SPEED_NORMAL)) {
DEBUG("[Error] I2C device not enabled\n");
return -1;
}
/* Acquire exclusive access */
i2c_acquire(dev->i2c_dev);
/* Check sensor ID */
uint8_t checkid;
i2c_read_reg(dev->i2c_dev, BMP180_ADDR, BMP180_REGISTER_ID, &checkid);
if (checkid != 0x55) {
DEBUG("[Error] Wrong device ID\n");
i2c_release(dev->i2c_dev);
return -1;
}
/* adding delay before reading calibration values to avoid timing issues */
xtimer_usleep(BMP180_ULTRALOWPOWER_DELAY);
uint8_t buffer[22] = {0};
/* Read calibration values, using contiguous register addresses */
if (i2c_read_regs(dev->i2c_dev, BMP180_ADDR, BMP180_CALIBRATION_AC1, buffer, 22) < 0) {
DEBUG("[Error] Cannot read calibration registers.\n");
i2c_release(dev->i2c_dev);
return -1;
}
dev->calibration.ac1 = (int16_t)(buffer[0] << 8) | buffer[1];
dev->calibration.ac2 = (int16_t)(buffer[2] << 8) | buffer[3];
dev->calibration.ac3 = (int16_t)(buffer[4] << 8) | buffer[4];
dev->calibration.ac4 = (uint16_t)(buffer[6] << 8) | buffer[7];
dev->calibration.ac5 = (uint16_t)(buffer[8] << 8) | buffer[9];
dev->calibration.ac6 = (uint16_t)(buffer[10] << 8) | buffer[11];
dev->calibration.b1 = (int16_t)(buffer[12] << 8) | buffer[13];
dev->calibration.b2 = (int16_t)(buffer[14] << 8) | buffer[15];
dev->calibration.mb = (int16_t)(buffer[16] << 8) | buffer[17];
dev->calibration.mc = (int16_t)(buffer[18] << 8) | buffer[19];
dev->calibration.md = (int16_t)(buffer[20] << 8) | buffer[21];
/* Release I2C device */
i2c_release(dev->i2c_dev);
DEBUG("AC1: %i\n", (int)dev->calibration.ac1);
DEBUG("AC2: %i\n", (int)dev->calibration.ac2);
DEBUG("AC3: %i\n", (int)dev->calibration.ac3);
DEBUG("AC4: %i\n", (int)dev->calibration.ac4);
DEBUG("AC5: %i\n", (int)dev->calibration.ac5);
DEBUG("AC6: %i\n", (int)dev->calibration.ac6);
DEBUG("B1: %i\n", (int)dev->calibration.b1);
DEBUG("B2: %i\n", (int)dev->calibration.b2);
DEBUG("MB: %i\n", (int)dev->calibration.mb);
DEBUG("MC: %i\n", (int)dev->calibration.mc);
DEBUG("MD: %i\n", (int)dev->calibration.md);
return 0;
}
int bmp180_read_temperature(bmp180_t *dev, int32_t *temperature)
{
int32_t ut, b5;
/* Acquire exclusive access */
i2c_acquire(dev->i2c_dev);
/* Read uncompensated value */
_read_ut(dev, &ut);
/* Compute true temperature value following datasheet formulas */
_compute_b5(dev, ut, &b5);
*temperature = (b5 + 8) >> 4;
/* Release I2C device */
i2c_release(dev->i2c_dev);
return 0;
}
int bmp180_read_pressure(bmp180_t *dev, int32_t *pressure)
{
int32_t ut = 0, up = 0, x1, x2, x3, b3, b5, b6, p;
uint32_t b4, b7;
/* Acquire exclusive access */
i2c_acquire(dev->i2c_dev);
/* Read uncompensated values: first temperature, second pressure */
_read_ut(dev, &ut);
_read_up(dev, &up);
/* Compute true pressure value following datasheet formulas */
_compute_b5(dev, ut, &b5);
b6 = b5 - 4000;
x1 = ((int32_t)dev->calibration.b2 * ((b6 * b6) >> 12)) >> 11;
x2 = ((int32_t)dev->calibration.ac2 * b6) >> 11;
x3 = x1 + x2;
b3 = ((((int32_t)dev->calibration.ac1*4 + x3) << dev->oversampling) + 2) >> 2;
x1 = ((int32_t)dev->calibration.ac3 * b6) >> 13;
x2 = ((int32_t)dev->calibration.b1 * (b6 * b6) >> 12) >> 16;
x3 = ((x1 + x2) + 2) >> 2;
b4 = (int32_t)dev->calibration.ac4 * (uint32_t)(x3+32768) >> 15;
b7 = ((uint32_t)up - b3) * (uint32_t)(50000UL >> dev->oversampling);
if (b7 < 0x80000000) {
p = (b7 * 2) / b4;
}
else {
p = (b7 / b4) * 2;
}
x1 = (p >> 8) * (p >> 8);
x1 = (x1 * 3038) >> 16;
x2 = (-7357 * p) >> 16;
*pressure = p + ((x1 + x2 + 3791) >> 4);
/* release I2C device */
i2c_release(dev->i2c_dev);
return 0;
}
int bmp180_altitude(bmp180_t *dev, int32_t pressure_0, int32_t *altitude)
{
int32_t p;
bmp180_read_pressure(dev, &p);
*altitude = (int32_t)(44330.0 * (1.0 - pow((double)p / pressure_0, 0.1903)));
return 0;
}
int bmp180_sealevel_pressure(bmp180_t *dev, int32_t altitude, int32_t *pressure_0)
{
int32_t p;
bmp180_read_pressure(dev, &p);
*pressure_0 = (int32_t)((double)p / pow(1.0 - (altitude / 44330.0), 5.255));
return 0;
}
/*------------------------------------------------------------------------------------*/
/* Internal functions */
/*------------------------------------------------------------------------------------*/
static int _read_ut(bmp180_t *dev, int32_t *output)
{
/* Read UT (Uncompsensated Temperature value) */
uint8_t ut[2] = {0};
uint8_t control[2] = { BMP180_REGISTER_CONTROL, BMP180_TEMPERATURE_COMMAND };
i2c_write_bytes(dev->i2c_dev, BMP180_ADDR, control, 2);
xtimer_usleep(BMP180_ULTRALOWPOWER_DELAY);
if (i2c_read_regs(dev->i2c_dev, BMP180_ADDR, BMP180_REGISTER_DATA, ut, 2) < 0) {
DEBUG("[Error] Cannot read uncompensated temperature.\n");
i2c_release(dev->i2c_dev);
return -1;
}
*output = ( ut[0] << 8 ) | ut[1];
DEBUG("UT: %i\n", (int)*output);
return 0;
}
static int _read_up(bmp180_t *dev, int32_t *output)
{
/* Read UP (Uncompsensated Pressure value) */
uint8_t up[3] = {0};
uint8_t control[2] = { BMP180_REGISTER_CONTROL, BMP180_PRESSURE_COMMAND | (dev->oversampling & 0x3) << 6 };
i2c_write_bytes(dev->i2c_dev, BMP180_ADDR, control, 2);
switch (dev->oversampling) {
case BMP180_ULTRALOWPOWER:
xtimer_usleep(BMP180_ULTRALOWPOWER_DELAY);
break;
case BMP180_STANDARD:
xtimer_usleep(BMP180_STANDARD_DELAY);
break;
case BMP180_HIGHRES:
xtimer_usleep(BMP180_HIGHRES_DELAY);
break;
case BMP180_ULTRAHIGHRES:
xtimer_usleep(BMP180_ULTRAHIGHRES_DELAY);
break;
default:
xtimer_usleep(BMP180_ULTRALOWPOWER_DELAY);
break;
}
if (i2c_read_regs(dev->i2c_dev, BMP180_ADDR, BMP180_REGISTER_DATA, up, 3) < 0) {
DEBUG("[Error] Cannot read uncompensated pressure.\n");
i2c_release(dev->i2c_dev);
return -1;
}
*output = ((up[0] << 16) | (up[1] << 8) | up[2]) >> (8 - dev->oversampling);
DEBUG("UP: %i\n", (int)*output);
return 0;
}
static int _compute_b5(bmp180_t *dev, int32_t ut, int32_t *output)
{
int32_t x1, x2;
x1 = (ut - dev->calibration.ac6) * dev->calibration.ac5 >> 15;
x2 = (dev->calibration.mc << 11) / (x1 + dev->calibration.md);
*output = x1 + x2;
return 0;
}