RE: [PATCH] Support for the pressure sensor BMP085 from BoschSensortec.

From: Datta, Shubhrajyoti
Date: Mon Jun 21 2010 - 04:53:29 EST



> -----Original Message-----
> From: Datta, Shubhrajyoti
> Sent: Monday, June 21, 2010 12:15 PM
> To: 'Christoph Mair'; Jonathan Cameron
> Cc: linux-kernel@xxxxxxxxxxxxxxx; Andrew Morton; Stefan Schmidt
> Subject: RE: [PATCH] Support for the pressure sensor BMP085 from Bosch
> Sensortec.
>
>
>
> > -----Original Message-----
> > From: Christoph Mair [mailto:christoph.mair@xxxxxxxxx]
> > Sent: Monday, June 21, 2010 2:21 AM
> > To: Jonathan Cameron
> > Cc: linux-kernel@xxxxxxxxxxxxxxx; Andrew Morton; Stefan Schmidt; Datta,
> > Shubhrajyoti; Christoph Mair
> > Subject: [PATCH] Support for the pressure sensor BMP085 from Bosch
> > Sensortec.
> >
> > This driver adds support for the BMP085 digital pressure sensor
> > from Bosch Sensortec. It exposes a sysfs api to userspace where
> > pressure and temperature measurement results can be read from the
> > pressure0_input and temp0_input file. The chip is able to calculate
> > the average of up to eight samples to increase the accuracy.
> > This feature can be controlled by writing to the oversampling file.
> >
> > Signed-off-by: Christoph Mair <christoph.mair@xxxxxxxxx>
> > Acked-by: Jonathan Cameron <jic23@xxxxxxxxx>
> > ---
> > drivers/misc/Kconfig | 10 +
> > drivers/misc/Makefile | 1 +
> > drivers/misc/bmp085.c | 455
> > +++++++++++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 466 insertions(+), 0 deletions(-)
> > create mode 100644 drivers/misc/bmp085.c
> >
> > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> > index 26386a9..9df8d3e 100644
> > --- a/drivers/misc/Kconfig
> > +++ b/drivers/misc/Kconfig
> > @@ -353,6 +353,16 @@ config VMWARE_BALLOON
> > To compile this driver as a module, choose M here: the
> > module will be called vmware_balloon.
> >
> > +config BMP085
> > + tristate "BMP085 digital pressure sensor"
> > + depends on I2C && SYSFS
> > + help
> > + If you say yes here you get support for the Bosch Sensortec
> > + BMP086 digital pressure sensor.
> > +
> > + To compile this driver as a module, choose M here: the
> > + module will be called bmp085.
> > +
> > source "drivers/misc/c2port/Kconfig"
> > source "drivers/misc/eeprom/Kconfig"
> > source "drivers/misc/cb710/Kconfig"
> > diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> > index 6ed06a1..5623c54 100644
> > --- a/drivers/misc/Makefile
> > +++ b/drivers/misc/Makefile
> > @@ -31,3 +31,4 @@ obj-$(CONFIG_IWMC3200TOP) += iwmc3200top/
> > obj-y += eeprom/
> > obj-y += cb710/
> > obj-$(CONFIG_VMWARE_BALLOON) += vmware_balloon.o
> > +obj-$(CONFIG_BMP085) += bmp085.o
> > diff --git a/drivers/misc/bmp085.c b/drivers/misc/bmp085.c
> > new file mode 100644
> > index 0000000..16a2b2c
> > --- /dev/null
> > +++ b/drivers/misc/bmp085.c
> > @@ -0,0 +1,455 @@
> > +/* Copyright (c) 2010 Christoph Mair <christoph.mair@xxxxxxxxx>
> > +
> > + 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;
> > + unsigned long last_temp_measurement;
> The size of long is arch dependent so using something like s32 etc may be
> used.
> > + 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<<1));

/*From the Datasheet
* Oversampling (osrs)
* Measurement | Control register | conversion time[ms]
* Pressure (osrs 0 ) |0x34 |4.5
* Pressure (osrs 1) |0x74 |7.5
* Pressure (osrs 2) |0xB4 |13.5
* Pressure (osrs 3) |0xF4 |25.5
*/

So I think (2+(3 << data->oversampling_setting)) should also work.


> > +
> > + /* 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 interlan 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@xxxxxxxxx");
> > +MODULE_DESCRIPTION("BMP085 driver");
> > +MODULE_LICENSE("GPL");
> > +
> > +module_init(bmp085_init);
> > +module_exit(bmp085_exit);
> > --
> > 1.7.1

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