25985edced
Fixes generated by 'codespell' and manually reviewed. Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
484 lines
13 KiB
C
484 lines
13 KiB
C
/* Copyright (c) 2010 Christoph Mair <christoph.mair@gmail.com>
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This driver supports the bmp085 digital barometric pressure
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and temperature sensor from Bosch Sensortec. The datasheet
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is available from their website:
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http://www.bosch-sensortec.com/content/language1/downloads/BST-BMP085-DS000-05.pdf
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A pressure measurement is issued by reading from pressure0_input.
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The return value ranges from 30000 to 110000 pascal with a resulution
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of 1 pascal (0.01 millibar) which enables measurements from 9000m above
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to 500m below sea level.
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The temperature can be read from temp0_input. Values range from
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-400 to 850 representing the ambient temperature in degree celsius
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multiplied by 10.The resolution is 0.1 celsius.
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Because ambient pressure is temperature dependent, a temperature
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measurement will be executed automatically even if the user is reading
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from pressure0_input. This happens if the last temperature measurement
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has been executed more then one second ago.
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To decrease RMS noise from pressure measurements, the bmp085 can
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autonomously calculate the average of up to eight samples. This is
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set up by writing to the oversampling sysfs file. Accepted values
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are 0, 1, 2 and 3. 2^x when x is the value written to this file
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specifies the number of samples used to calculate the ambient pressure.
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RMS noise is specified with six pascal (without averaging) and decreases
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down to 3 pascal when using an oversampling setting of 3.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/i2c.h>
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#include <linux/slab.h>
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#include <linux/delay.h>
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#define BMP085_I2C_ADDRESS 0x77
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#define BMP085_CHIP_ID 0x55
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#define BMP085_CALIBRATION_DATA_START 0xAA
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#define BMP085_CALIBRATION_DATA_LENGTH 11 /* 16 bit values */
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#define BMP085_CHIP_ID_REG 0xD0
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#define BMP085_VERSION_REG 0xD1
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#define BMP085_CTRL_REG 0xF4
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#define BMP085_TEMP_MEASUREMENT 0x2E
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#define BMP085_PRESSURE_MEASUREMENT 0x34
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#define BMP085_CONVERSION_REGISTER_MSB 0xF6
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#define BMP085_CONVERSION_REGISTER_LSB 0xF7
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#define BMP085_CONVERSION_REGISTER_XLSB 0xF8
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#define BMP085_TEMP_CONVERSION_TIME 5
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#define BMP085_CLIENT_NAME "bmp085"
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static const unsigned short normal_i2c[] = { BMP085_I2C_ADDRESS,
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I2C_CLIENT_END };
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struct bmp085_calibration_data {
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s16 AC1, AC2, AC3;
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u16 AC4, AC5, AC6;
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s16 B1, B2;
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s16 MB, MC, MD;
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};
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/* Each client has this additional data */
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struct bmp085_data {
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struct i2c_client *client;
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struct mutex lock;
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struct bmp085_calibration_data calibration;
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u32 raw_temperature;
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u32 raw_pressure;
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unsigned char oversampling_setting;
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u32 last_temp_measurement;
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s32 b6; /* calculated temperature correction coefficient */
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};
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static s32 bmp085_read_calibration_data(struct i2c_client *client)
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{
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u16 tmp[BMP085_CALIBRATION_DATA_LENGTH];
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struct bmp085_data *data = i2c_get_clientdata(client);
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struct bmp085_calibration_data *cali = &(data->calibration);
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s32 status = i2c_smbus_read_i2c_block_data(client,
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BMP085_CALIBRATION_DATA_START,
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BMP085_CALIBRATION_DATA_LENGTH*sizeof(u16),
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(u8 *)tmp);
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if (status < 0)
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return status;
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if (status != BMP085_CALIBRATION_DATA_LENGTH*sizeof(u16))
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return -EIO;
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cali->AC1 = be16_to_cpu(tmp[0]);
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cali->AC2 = be16_to_cpu(tmp[1]);
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cali->AC3 = be16_to_cpu(tmp[2]);
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cali->AC4 = be16_to_cpu(tmp[3]);
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cali->AC5 = be16_to_cpu(tmp[4]);
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cali->AC6 = be16_to_cpu(tmp[5]);
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cali->B1 = be16_to_cpu(tmp[6]);
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cali->B2 = be16_to_cpu(tmp[7]);
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cali->MB = be16_to_cpu(tmp[8]);
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cali->MC = be16_to_cpu(tmp[9]);
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cali->MD = be16_to_cpu(tmp[10]);
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return 0;
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}
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static s32 bmp085_update_raw_temperature(struct bmp085_data *data)
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{
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u16 tmp;
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s32 status;
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mutex_lock(&data->lock);
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status = i2c_smbus_write_byte_data(data->client, BMP085_CTRL_REG,
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BMP085_TEMP_MEASUREMENT);
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if (status != 0) {
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dev_err(&data->client->dev,
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"Error while requesting temperature measurement.\n");
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goto exit;
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}
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msleep(BMP085_TEMP_CONVERSION_TIME);
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status = i2c_smbus_read_i2c_block_data(data->client,
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BMP085_CONVERSION_REGISTER_MSB, sizeof(tmp), (u8 *)&tmp);
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if (status < 0)
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goto exit;
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if (status != sizeof(tmp)) {
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dev_err(&data->client->dev,
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"Error while reading temperature measurement result\n");
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status = -EIO;
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goto exit;
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}
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data->raw_temperature = be16_to_cpu(tmp);
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data->last_temp_measurement = jiffies;
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status = 0; /* everything ok, return 0 */
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exit:
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mutex_unlock(&data->lock);
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return status;
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}
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static s32 bmp085_update_raw_pressure(struct bmp085_data *data)
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{
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u32 tmp = 0;
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s32 status;
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mutex_lock(&data->lock);
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status = i2c_smbus_write_byte_data(data->client, BMP085_CTRL_REG,
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BMP085_PRESSURE_MEASUREMENT + (data->oversampling_setting<<6));
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if (status != 0) {
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dev_err(&data->client->dev,
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"Error while requesting pressure measurement.\n");
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goto exit;
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}
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/* wait for the end of conversion */
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msleep(2+(3 << data->oversampling_setting));
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/* copy data into a u32 (4 bytes), but skip the first byte. */
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status = i2c_smbus_read_i2c_block_data(data->client,
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BMP085_CONVERSION_REGISTER_MSB, 3, ((u8 *)&tmp)+1);
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if (status < 0)
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goto exit;
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if (status != 3) {
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dev_err(&data->client->dev,
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"Error while reading pressure measurement results\n");
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status = -EIO;
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goto exit;
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}
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data->raw_pressure = be32_to_cpu((tmp));
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data->raw_pressure >>= (8-data->oversampling_setting);
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status = 0; /* everything ok, return 0 */
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exit:
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mutex_unlock(&data->lock);
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return status;
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}
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/*
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* This function starts the temperature measurement and returns the value
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* in tenth of a degree celsius.
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*/
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static s32 bmp085_get_temperature(struct bmp085_data *data, int *temperature)
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{
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struct bmp085_calibration_data *cali = &data->calibration;
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long x1, x2;
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int status;
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status = bmp085_update_raw_temperature(data);
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if (status != 0)
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goto exit;
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x1 = ((data->raw_temperature - cali->AC6) * cali->AC5) >> 15;
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x2 = (cali->MC << 11) / (x1 + cali->MD);
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data->b6 = x1 + x2 - 4000;
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/* if NULL just update b6. Used for pressure only measurements */
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if (temperature != NULL)
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*temperature = (x1+x2+8) >> 4;
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exit:
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return status;;
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}
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/*
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* This function starts the pressure measurement and returns the value
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* in millibar. Since the pressure depends on the ambient temperature,
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* a temperature measurement is executed if the last known value is older
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* than one second.
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*/
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static s32 bmp085_get_pressure(struct bmp085_data *data, int *pressure)
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{
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struct bmp085_calibration_data *cali = &data->calibration;
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s32 x1, x2, x3, b3;
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u32 b4, b7;
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s32 p;
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int status;
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/* alt least every second force an update of the ambient temperature */
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if (data->last_temp_measurement + 1*HZ < jiffies) {
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status = bmp085_get_temperature(data, NULL);
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if (status != 0)
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goto exit;
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}
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status = bmp085_update_raw_pressure(data);
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if (status != 0)
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goto exit;
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x1 = (data->b6 * data->b6) >> 12;
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x1 *= cali->B2;
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x1 >>= 11;
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x2 = cali->AC2 * data->b6;
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x2 >>= 11;
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x3 = x1 + x2;
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b3 = (((((s32)cali->AC1) * 4 + x3) << data->oversampling_setting) + 2);
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b3 >>= 2;
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x1 = (cali->AC3 * data->b6) >> 13;
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x2 = (cali->B1 * ((data->b6 * data->b6) >> 12)) >> 16;
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x3 = (x1 + x2 + 2) >> 2;
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b4 = (cali->AC4 * (u32)(x3 + 32768)) >> 15;
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b7 = ((u32)data->raw_pressure - b3) *
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(50000 >> data->oversampling_setting);
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p = ((b7 < 0x80000000) ? ((b7 << 1) / b4) : ((b7 / b4) * 2));
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x1 = p >> 8;
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x1 *= x1;
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x1 = (x1 * 3038) >> 16;
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x2 = (-7357 * p) >> 16;
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p += (x1 + x2 + 3791) >> 4;
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*pressure = p;
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exit:
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return status;
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}
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/*
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* This function sets the chip-internal oversampling. Valid values are 0..3.
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* The chip will use 2^oversampling samples for internal averaging.
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* This influences the measurement time and the accuracy; larger values
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* increase both. The datasheet gives on overview on how measurement time,
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* accuracy and noise correlate.
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*/
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static void bmp085_set_oversampling(struct bmp085_data *data,
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unsigned char oversampling)
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{
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if (oversampling > 3)
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oversampling = 3;
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data->oversampling_setting = oversampling;
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}
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/*
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* Returns the currently selected oversampling. Range: 0..3
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*/
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static unsigned char bmp085_get_oversampling(struct bmp085_data *data)
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{
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return data->oversampling_setting;
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}
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/* sysfs callbacks */
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static ssize_t set_oversampling(struct device *dev,
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struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct i2c_client *client = to_i2c_client(dev);
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struct bmp085_data *data = i2c_get_clientdata(client);
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unsigned long oversampling;
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int success = strict_strtoul(buf, 10, &oversampling);
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if (success == 0) {
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bmp085_set_oversampling(data, oversampling);
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return count;
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}
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return success;
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}
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static ssize_t show_oversampling(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct i2c_client *client = to_i2c_client(dev);
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struct bmp085_data *data = i2c_get_clientdata(client);
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return sprintf(buf, "%u\n", bmp085_get_oversampling(data));
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}
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static DEVICE_ATTR(oversampling, S_IWUSR | S_IRUGO,
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show_oversampling, set_oversampling);
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static ssize_t show_temperature(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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int temperature;
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int status;
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struct i2c_client *client = to_i2c_client(dev);
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struct bmp085_data *data = i2c_get_clientdata(client);
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status = bmp085_get_temperature(data, &temperature);
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if (status != 0)
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return status;
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else
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return sprintf(buf, "%d\n", temperature);
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}
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static DEVICE_ATTR(temp0_input, S_IRUGO, show_temperature, NULL);
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static ssize_t show_pressure(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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int pressure;
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int status;
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struct i2c_client *client = to_i2c_client(dev);
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struct bmp085_data *data = i2c_get_clientdata(client);
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status = bmp085_get_pressure(data, &pressure);
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if (status != 0)
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return status;
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else
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return sprintf(buf, "%d\n", pressure);
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}
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static DEVICE_ATTR(pressure0_input, S_IRUGO, show_pressure, NULL);
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static struct attribute *bmp085_attributes[] = {
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&dev_attr_temp0_input.attr,
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&dev_attr_pressure0_input.attr,
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&dev_attr_oversampling.attr,
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NULL
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};
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static const struct attribute_group bmp085_attr_group = {
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.attrs = bmp085_attributes,
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};
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static int bmp085_detect(struct i2c_client *client, struct i2c_board_info *info)
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{
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if (client->addr != BMP085_I2C_ADDRESS)
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return -ENODEV;
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if (i2c_smbus_read_byte_data(client, BMP085_CHIP_ID_REG) != BMP085_CHIP_ID)
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return -ENODEV;
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return 0;
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}
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static int bmp085_init_client(struct i2c_client *client)
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{
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unsigned char version;
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int status;
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struct bmp085_data *data = i2c_get_clientdata(client);
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data->client = client;
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status = bmp085_read_calibration_data(client);
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if (status != 0)
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goto exit;
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version = i2c_smbus_read_byte_data(client, BMP085_VERSION_REG);
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data->last_temp_measurement = 0;
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data->oversampling_setting = 3;
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mutex_init(&data->lock);
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dev_info(&data->client->dev, "BMP085 ver. %d.%d found.\n",
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(version & 0x0F), (version & 0xF0) >> 4);
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exit:
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return status;
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}
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static int __devinit bmp085_probe(struct i2c_client *client,
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const struct i2c_device_id *id)
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{
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struct bmp085_data *data;
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int err = 0;
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data = kzalloc(sizeof(struct bmp085_data), GFP_KERNEL);
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if (!data) {
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err = -ENOMEM;
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goto exit;
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}
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/* default settings after POR */
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data->oversampling_setting = 0x00;
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i2c_set_clientdata(client, data);
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/* Initialize the BMP085 chip */
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err = bmp085_init_client(client);
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if (err != 0)
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goto exit_free;
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/* Register sysfs hooks */
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err = sysfs_create_group(&client->dev.kobj, &bmp085_attr_group);
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if (err)
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goto exit_free;
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dev_info(&data->client->dev, "Successfully initialized bmp085!\n");
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goto exit;
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exit_free:
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kfree(data);
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exit:
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return err;
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}
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static int __devexit bmp085_remove(struct i2c_client *client)
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{
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sysfs_remove_group(&client->dev.kobj, &bmp085_attr_group);
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kfree(i2c_get_clientdata(client));
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return 0;
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}
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static const struct i2c_device_id bmp085_id[] = {
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{ "bmp085", 0 },
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{ }
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};
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MODULE_DEVICE_TABLE(i2c, bmp085_id);
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static struct i2c_driver bmp085_driver = {
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.driver = {
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.owner = THIS_MODULE,
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.name = "bmp085"
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},
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.id_table = bmp085_id,
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.probe = bmp085_probe,
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.remove = __devexit_p(bmp085_remove),
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.detect = bmp085_detect,
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.address_list = normal_i2c
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};
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static int __init bmp085_init(void)
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{
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return i2c_add_driver(&bmp085_driver);
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}
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static void __exit bmp085_exit(void)
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{
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i2c_del_driver(&bmp085_driver);
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}
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MODULE_AUTHOR("Christoph Mair <christoph.mair@gmail.com");
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MODULE_DESCRIPTION("BMP085 driver");
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MODULE_LICENSE("GPL");
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module_init(bmp085_init);
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module_exit(bmp085_exit);
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