diff options
Diffstat (limited to 'drivers/misc/bmp085.c')
| -rw-r--r-- | drivers/misc/bmp085.c | 482 |
1 files changed, 482 insertions, 0 deletions
diff --git a/drivers/misc/bmp085.c b/drivers/misc/bmp085.c new file mode 100644 index 00000000000..63ee4c1a531 --- /dev/null +++ b/drivers/misc/bmp085.c @@ -0,0 +1,482 @@ +/* Copyright (c) 2010 Christoph Mair <christoph.mair@gmail.com> + + This driver supports the bmp085 digital barometric pressure + and temperature sensor from Bosch Sensortec. The datasheet + is avaliable from their website: + http://www.bosch-sensortec.com/content/language1/downloads/BST-BMP085-DS000-05.pdf + + A pressure measurement is issued by reading from pressure0_input. + The return value ranges from 30000 to 110000 pascal with a resulution + of 1 pascal (0.01 millibar) which enables measurements from 9000m above + to 500m below sea level. + + The temperature can be read from temp0_input. Values range from + -400 to 850 representing the ambient temperature in degree celsius + multiplied by 10.The resolution is 0.1 celsius. + + Because ambient pressure is temperature dependent, a temperature + measurement will be executed automatically even if the user is reading + from pressure0_input. This happens if the last temperature measurement + has been executed more then one second ago. + + To decrease RMS noise from pressure measurements, the bmp085 can + autonomously calculate the average of up to eight samples. This is + set up by writing to the oversampling sysfs file. Accepted values + are 0, 1, 2 and 3. 2^x when x is the value written to this file + specifies the number of samples used to calculate the ambient pressure. + RMS noise is specified with six pascal (without averaging) and decreases + down to 3 pascal when using an oversampling setting of 3. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 2 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software + Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. +*/ + + +#include <linux/module.h> +#include <linux/init.h> +#include <linux/i2c.h> +#include <linux/slab.h> +#include <linux/delay.h> + + +#define BMP085_I2C_ADDRESS 0x77 +#define BMP085_CHIP_ID 0x55 + +#define BMP085_CALIBRATION_DATA_START 0xAA +#define BMP085_CALIBRATION_DATA_LENGTH 11 /* 16 bit values */ +#define BMP085_CHIP_ID_REG 0xD0 +#define BMP085_VERSION_REG 0xD1 +#define BMP085_CTRL_REG 0xF4 +#define BMP085_TEMP_MEASUREMENT 0x2E +#define BMP085_PRESSURE_MEASUREMENT 0x34 +#define BMP085_CONVERSION_REGISTER_MSB 0xF6 +#define BMP085_CONVERSION_REGISTER_LSB 0xF7 +#define BMP085_CONVERSION_REGISTER_XLSB 0xF8 +#define BMP085_TEMP_CONVERSION_TIME 5 + +#define BMP085_CLIENT_NAME "bmp085" + + +static const unsigned short normal_i2c[] = { BMP085_I2C_ADDRESS, + I2C_CLIENT_END }; + +struct bmp085_calibration_data { + s16 AC1, AC2, AC3; + u16 AC4, AC5, AC6; + s16 B1, B2; + s16 MB, MC, MD; +}; + + +/* Each client has this additional data */ +struct bmp085_data { + struct i2c_client *client; + struct mutex lock; + struct bmp085_calibration_data calibration; + u32 raw_temperature; + u32 raw_pressure; + unsigned char oversampling_setting; + u32 last_temp_measurement; + s32 b6; /* calculated temperature correction coefficient */ +}; + + +static s32 bmp085_read_calibration_data(struct i2c_client *client) +{ + u16 tmp[BMP085_CALIBRATION_DATA_LENGTH]; + struct bmp085_data *data = i2c_get_clientdata(client); + struct bmp085_calibration_data *cali = &(data->calibration); + s32 status = i2c_smbus_read_i2c_block_data(client, + BMP085_CALIBRATION_DATA_START, + BMP085_CALIBRATION_DATA_LENGTH*sizeof(u16), + (u8 *)tmp); + if (status < 0) + return status; + + if (status != BMP085_CALIBRATION_DATA_LENGTH*sizeof(u16)) + return -EIO; + + cali->AC1 = be16_to_cpu(tmp[0]); + cali->AC2 = be16_to_cpu(tmp[1]); + cali->AC3 = be16_to_cpu(tmp[2]); + cali->AC4 = be16_to_cpu(tmp[3]); + cali->AC5 = be16_to_cpu(tmp[4]); + cali->AC6 = be16_to_cpu(tmp[5]); + cali->B1 = be16_to_cpu(tmp[6]); + cali->B2 = be16_to_cpu(tmp[7]); + cali->MB = be16_to_cpu(tmp[8]); + cali->MC = be16_to_cpu(tmp[9]); + cali->MD = be16_to_cpu(tmp[10]); + return 0; +} + + +static s32 bmp085_update_raw_temperature(struct bmp085_data *data) +{ + u16 tmp; + s32 status; + + mutex_lock(&data->lock); + status = i2c_smbus_write_byte_data(data->client, BMP085_CTRL_REG, + BMP085_TEMP_MEASUREMENT); + if (status != 0) { + dev_err(&data->client->dev, + "Error while requesting temperature measurement.\n"); + goto exit; + } + msleep(BMP085_TEMP_CONVERSION_TIME); + + status = i2c_smbus_read_i2c_block_data(data->client, + BMP085_CONVERSION_REGISTER_MSB, sizeof(tmp), (u8 *)&tmp); + if (status < 0) + goto exit; + if (status != sizeof(tmp)) { + dev_err(&data->client->dev, + "Error while reading temperature measurement result\n"); + status = -EIO; + goto exit; + } + data->raw_temperature = be16_to_cpu(tmp); + data->last_temp_measurement = jiffies; + status = 0; /* everything ok, return 0 */ + +exit: + mutex_unlock(&data->lock); + return status; +} + +static s32 bmp085_update_raw_pressure(struct bmp085_data *data) +{ + u32 tmp = 0; + s32 status; + + mutex_lock(&data->lock); + status = i2c_smbus_write_byte_data(data->client, BMP085_CTRL_REG, + BMP085_PRESSURE_MEASUREMENT + (data->oversampling_setting<<6)); + if (status != 0) { + dev_err(&data->client->dev, + "Error while requesting pressure measurement.\n"); + goto exit; + } + + /* wait for the end of conversion */ + msleep(2+(3 << data->oversampling_setting)); + + /* copy data into a u32 (4 bytes), but skip the first byte. */ + status = i2c_smbus_read_i2c_block_data(data->client, + BMP085_CONVERSION_REGISTER_MSB, 3, ((u8 *)&tmp)+1); + if (status < 0) + goto exit; + if (status != 3) { + dev_err(&data->client->dev, + "Error while reading pressure measurement results\n"); + status = -EIO; + goto exit; + } + data->raw_pressure = be32_to_cpu((tmp)); + data->raw_pressure >>= (8-data->oversampling_setting); + status = 0; /* everything ok, return 0 */ + +exit: + mutex_unlock(&data->lock); + return status; +} + + +/* + * This function starts the temperature measurement and returns the value + * in tenth of a degree celsius. + */ +static s32 bmp085_get_temperature(struct bmp085_data *data, int *temperature) +{ + struct bmp085_calibration_data *cali = &data->calibration; + long x1, x2; + int status; + + status = bmp085_update_raw_temperature(data); + if (status != 0) + goto exit; + + x1 = ((data->raw_temperature - cali->AC6) * cali->AC5) >> 15; + x2 = (cali->MC << 11) / (x1 + cali->MD); + data->b6 = x1 + x2 - 4000; + /* if NULL just update b6. Used for pressure only measurements */ + if (temperature != NULL) + *temperature = (x1+x2+8) >> 4; + +exit: + return status;; +} + +/* + * This function starts the pressure measurement and returns the value + * in millibar. Since the pressure depends on the ambient temperature, + * a temperature measurement is executed if the last known value is older + * than one second. + */ +static s32 bmp085_get_pressure(struct bmp085_data *data, int *pressure) +{ + struct bmp085_calibration_data *cali = &data->calibration; + s32 x1, x2, x3, b3; + u32 b4, b7; + s32 p; + int status; + + /* alt least every second force an update of the ambient temperature */ + if (data->last_temp_measurement + 1*HZ < jiffies) { + status = bmp085_get_temperature(data, NULL); + if (status != 0) + goto exit; + } + + status = bmp085_update_raw_pressure(data); + if (status != 0) + goto exit; + + x1 = (data->b6 * data->b6) >> 12; + x1 *= cali->B2; + x1 >>= 11; + + x2 = cali->AC2 * data->b6; + x2 >>= 11; + + x3 = x1 + x2; + + b3 = (((((s32)cali->AC1) * 4 + x3) << data->oversampling_setting) + 2); + b3 >>= 2; + + x1 = (cali->AC3 * data->b6) >> 13; + x2 = (cali->B1 * ((data->b6 * data->b6) >> 12)) >> 16; + x3 = (x1 + x2 + 2) >> 2; + b4 = (cali->AC4 * (u32)(x3 + 32768)) >> 15; + + b7 = ((u32)data->raw_pressure - b3) * + (50000 >> data->oversampling_setting); + p = ((b7 < 0x80000000) ? ((b7 << 1) / b4) : ((b7 / b4) * 2)); + + x1 = p >> 8; + x1 *= x1; + x1 = (x1 * 3038) >> 16; + x2 = (-7357 * p) >> 16; + p += (x1 + x2 + 3791) >> 4; + + *pressure = p; + +exit: + return status; +} + +/* + * This function sets the chip-internal oversampling. Valid values are 0..3. + * The chip will use 2^oversampling samples for internal averaging. + * This influences the measurement time and the accuracy; larger values + * increase both. The datasheet gives on overview on how measurement time, + * accuracy and noise correlate. + */ +static void bmp085_set_oversampling(struct bmp085_data *data, + unsigned char oversampling) +{ + if (oversampling > 3) + oversampling = 3; + data->oversampling_setting = oversampling; +} + +/* + * Returns the currently selected oversampling. Range: 0..3 + */ +static unsigned char bmp085_get_oversampling(struct bmp085_data *data) +{ + return data->oversampling_setting; +} + +/* sysfs callbacks */ +static ssize_t set_oversampling(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + struct i2c_client *client = to_i2c_client(dev); + struct bmp085_data *data = i2c_get_clientdata(client); + unsigned long oversampling; + int success = strict_strtoul(buf, 10, &oversampling); + if (success == 0) { + bmp085_set_oversampling(data, oversampling); + return count; + } + return success; +} + +static ssize_t show_oversampling(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct i2c_client *client = to_i2c_client(dev); + struct bmp085_data *data = i2c_get_clientdata(client); + return sprintf(buf, "%u\n", bmp085_get_oversampling(data)); +} +static DEVICE_ATTR(oversampling, S_IWUSR | S_IRUGO, + show_oversampling, set_oversampling); + + +static ssize_t show_temperature(struct device *dev, + struct device_attribute *attr, char *buf) +{ + int temperature; + int status; + struct i2c_client *client = to_i2c_client(dev); + struct bmp085_data *data = i2c_get_clientdata(client); + + status = bmp085_get_temperature(data, &temperature); + if (status != 0) + return status; + else + return sprintf(buf, "%d\n", temperature); +} +static DEVICE_ATTR(temp0_input, S_IRUGO, show_temperature, NULL); + + +static ssize_t show_pressure(struct device *dev, + struct device_attribute *attr, char *buf) +{ + int pressure; + int status; + struct i2c_client *client = to_i2c_client(dev); + struct bmp085_data *data = i2c_get_clientdata(client); + + status = bmp085_get_pressure(data, &pressure); + if (status != 0) + return status; + else + return sprintf(buf, "%d\n", pressure); +} +static DEVICE_ATTR(pressure0_input, S_IRUGO, show_pressure, NULL); + + +static struct attribute *bmp085_attributes[] = { + &dev_attr_temp0_input.attr, + &dev_attr_pressure0_input.attr, + &dev_attr_oversampling.attr, + NULL +}; + +static const struct attribute_group bmp085_attr_group = { + .attrs = bmp085_attributes, +}; + +static int bmp085_detect(struct i2c_client *client, struct i2c_board_info *info) +{ + if (client->addr != BMP085_I2C_ADDRESS) + return -ENODEV; + + if (i2c_smbus_read_byte_data(client, BMP085_CHIP_ID_REG) != BMP085_CHIP_ID) + return -ENODEV; + + return 0; +} + +static int bmp085_init_client(struct i2c_client *client) +{ + unsigned char version; + int status; + struct bmp085_data *data = i2c_get_clientdata(client); + data->client = client; + status = bmp085_read_calibration_data(client); + if (status != 0) + goto exit; + version = i2c_smbus_read_byte_data(client, BMP085_VERSION_REG); + data->last_temp_measurement = 0; + data->oversampling_setting = 3; + mutex_init(&data->lock); + dev_info(&data->client->dev, "BMP085 ver. %d.%d found.\n", + (version & 0x0F), (version & 0xF0) >> 4); +exit: + return status; +} + +static int bmp085_probe(struct i2c_client *client, + const struct i2c_device_id *id) +{ + struct bmp085_data *data; + int err = 0; + + data = kzalloc(sizeof(struct bmp085_data), GFP_KERNEL); + if (!data) { + err = -ENOMEM; + goto exit; + } + + /* default settings after POR */ + data->oversampling_setting = 0x00; + + i2c_set_clientdata(client, data); + + /* Initialize the BMP085 chip */ + err = bmp085_init_client(client); + if (err != 0) + goto exit_free; + + /* Register sysfs hooks */ + err = sysfs_create_group(&client->dev.kobj, &bmp085_attr_group); + if (err) + goto exit_free; + + dev_info(&data->client->dev, "Succesfully initialized bmp085!\n"); + goto exit; + +exit_free: + kfree(data); +exit: + return err; +} + +static int bmp085_remove(struct i2c_client *client) +{ + sysfs_remove_group(&client->dev.kobj, &bmp085_attr_group); + kfree(i2c_get_clientdata(client)); + return 0; +} + +static const struct i2c_device_id bmp085_id[] = { + { "bmp085", 0 }, + { } +}; + +static struct i2c_driver bmp085_driver = { + .driver = { + .owner = THIS_MODULE, + .name = "bmp085" + }, + .id_table = bmp085_id, + .probe = bmp085_probe, + .remove = bmp085_remove, + + .detect = bmp085_detect, + .address_list = normal_i2c +}; + +static int __init bmp085_init(void) +{ + return i2c_add_driver(&bmp085_driver); +} + +static void __exit bmp085_exit(void) +{ + i2c_del_driver(&bmp085_driver); +} + + +MODULE_AUTHOR("Christoph Mair <christoph.mair@gmail.com"); +MODULE_DESCRIPTION("BMP085 driver"); +MODULE_LICENSE("GPL"); + +module_init(bmp085_init); +module_exit(bmp085_exit); |