/* Copyright (c) 2010 Christoph Mair <christoph.mair@gmail.com> * Copyright (c) 2012 Bosch Sensortec GmbH * Copyright (c) 2012 Unixphere AB * * This driver supports the bmp085 and bmp18x digital barometric pressure * and temperature sensors from Bosch Sensortec. The datasheets * are available from their website: * http://www.bosch-sensortec.com/content/language1/downloads/BST-BMP085-DS000-05.pdf * http://www.bosch-sensortec.com/content/language1/downloads/BST-BMP180-DS000-07.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/device.h> #include <linux/init.h> #include <linux/slab.h> #include <linux/delay.h> #include <linux/of.h> #include "bmp085.h" #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_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 struct bmp085_calibration_data { s16 AC1, AC2, AC3; u16 AC4, AC5, AC6; s16 B1, B2; s16 MB, MC, MD; }; struct bmp085_data { struct device *dev; struct regmap *regmap; struct mutex lock; struct bmp085_calibration_data calibration; u8 oversampling_setting; u32 raw_temperature; u32 raw_pressure; u32 temp_measurement_period; unsigned long last_temp_measurement; u8 chip_id; s32 b6; /* calculated temperature correction coefficient */ }; static s32 bmp085_read_calibration_data(struct bmp085_data *data) { u16 tmp[BMP085_CALIBRATION_DATA_LENGTH]; struct bmp085_calibration_data *cali = &(data->calibration); s32 status = regmap_bulk_read(data->regmap, BMP085_CALIBRATION_DATA_START, (u8 *)tmp, (BMP085_CALIBRATION_DATA_LENGTH << 1)); if (status < 0) return status; 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 = regmap_write(data->regmap, BMP085_CTRL_REG, BMP085_TEMP_MEASUREMENT); if (status < 0) { dev_err(data->dev, "Error while requesting temperature measurement.\n"); goto exit; } msleep(BMP085_TEMP_CONVERSION_TIME); status = regmap_bulk_read(data->regmap, BMP085_CONVERSION_REGISTER_MSB, &tmp, sizeof(tmp)); if (status < 0) { dev_err(data->dev, "Error while reading temperature measurement result\n"); 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 = regmap_write(data->regmap, BMP085_CTRL_REG, BMP085_PRESSURE_MEASUREMENT + (data->oversampling_setting << 6)); if (status < 0) { dev_err(data->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 = regmap_bulk_read(data->regmap, BMP085_CONVERSION_REGISTER_MSB, ((u8 *)&tmp)+1, 3); if (status < 0) { dev_err(data->dev, "Error while reading pressure measurement results\n"); 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 according to the given temperature * measurement period (default is 1 sec boundary). This period could vary * and needs to be adjusted according to the sensor environment, i.e. if big * temperature variations then the temperature needs to be read out often. */ 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 == 0) || time_is_before_jiffies(data->last_temp_measurement + 1*HZ)) { status = bmp085_get_temperature(data, NULL); if (status < 0) return status; } status = bmp085_update_raw_pressure(data); if (status < 0) return status; 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; return 0; } /* * 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 an 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 bmp085_data *data = dev_get_drvdata(dev); unsigned long oversampling; int err = kstrtoul(buf, 10, &oversampling); if (err == 0) { mutex_lock(&data->lock); bmp085_set_oversampling(data, oversampling); mutex_unlock(&data->lock); return count; } return err; } static ssize_t show_oversampling(struct device *dev, struct device_attribute *attr, char *buf) { struct bmp085_data *data = dev_get_drvdata(dev); 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 bmp085_data *data = dev_get_drvdata(dev); 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 bmp085_data *data = dev_get_drvdata(dev); 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, }; int bmp085_detect(struct device *dev) { struct bmp085_data *data = dev_get_drvdata(dev); unsigned int id; int ret; ret = regmap_read(data->regmap, BMP085_CHIP_ID_REG, &id); if (ret < 0) return ret; if (id != data->chip_id) return -ENODEV; return 0; } EXPORT_SYMBOL_GPL(bmp085_detect); static void bmp085_get_of_properties(struct bmp085_data *data) { #ifdef CONFIG_OF struct device_node *np = data->dev->of_node; u32 prop; if (!np) return; if (!of_property_read_u32(np, "chip-id", &prop)) data->chip_id = prop & 0xff; if (!of_property_read_u32(np, "temp-measurement-period", &prop)) data->temp_measurement_period = (prop/100)*HZ; if (!of_property_read_u32(np, "default-oversampling", &prop)) data->oversampling_setting = prop & 0xff; #endif } static int bmp085_init_client(struct bmp085_data *data) { int status = bmp085_read_calibration_data(data); if (status < 0) return status; /* default settings */ data->chip_id = BMP085_CHIP_ID; data->last_temp_measurement = 0; data->temp_measurement_period = 1*HZ; data->oversampling_setting = 3; bmp085_get_of_properties(data); mutex_init(&data->lock); return 0; } struct regmap_config bmp085_regmap_config = { .reg_bits = 8, .val_bits = 8 }; EXPORT_SYMBOL_GPL(bmp085_regmap_config); int bmp085_probe(struct device *dev, struct regmap *regmap) { struct bmp085_data *data; int err = 0; data = kzalloc(sizeof(struct bmp085_data), GFP_KERNEL); if (!data) { err = -ENOMEM; goto exit; } dev_set_drvdata(dev, data); data->dev = dev; data->regmap = regmap; /* Initialize the BMP085 chip */ err = bmp085_init_client(data); if (err < 0) goto exit_free; err = bmp085_detect(dev); if (err < 0) { dev_err(dev, "%s: chip_id failed!\n", BMP085_NAME); goto exit_free; } /* Register sysfs hooks */ err = sysfs_create_group(&dev->kobj, &bmp085_attr_group); if (err) goto exit_free; dev_info(dev, "Successfully initialized %s!\n", BMP085_NAME); return 0; exit_free: kfree(data); exit: return err; } EXPORT_SYMBOL_GPL(bmp085_probe); int bmp085_remove(struct device *dev) { struct bmp085_data *data = dev_get_drvdata(dev); sysfs_remove_group(&data->dev->kobj, &bmp085_attr_group); kfree(data); return 0; } EXPORT_SYMBOL_GPL(bmp085_remove); MODULE_AUTHOR("Christoph Mair <christoph.mair@gmail.com>"); MODULE_DESCRIPTION("BMP085 driver"); MODULE_LICENSE("GPL");