diff options
Diffstat (limited to 'drivers/iio/humidity/si7020.c')
| -rw-r--r-- | drivers/iio/humidity/si7020.c | 174 |
1 files changed, 174 insertions, 0 deletions
diff --git a/drivers/iio/humidity/si7020.c b/drivers/iio/humidity/si7020.c new file mode 100644 index 000000000..1b2ec8df1 --- /dev/null +++ b/drivers/iio/humidity/si7020.c @@ -0,0 +1,174 @@ +/* + * si7020.c - Silicon Labs Si7013/20/21 Relative Humidity and Temp Sensors + * Copyright (c) 2013,2014 Uplogix, Inc. + * David Barksdale <dbarksdale@uplogix.com> + * + * This program is free software; you can redistribute it and/or modify it + * under the terms and conditions of the GNU General Public License, + * version 2, as published by the Free Software Foundation. + * + * 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. + */ + +/* + * The Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors + * are i2c devices which have an identical programming interface for + * measuring relative humidity and temperature. The Si7013 has an additional + * temperature input which this driver does not support. + * + * Data Sheets: + * Si7013: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7013.pdf + * Si7020: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7020.pdf + * Si7021: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7021.pdf + */ + +#include <linux/delay.h> +#include <linux/i2c.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/sysfs.h> + +#include <linux/iio/iio.h> +#include <linux/iio/sysfs.h> + +/* Measure Relative Humidity, Hold Master Mode */ +#define SI7020CMD_RH_HOLD 0xE5 +/* Measure Temperature, Hold Master Mode */ +#define SI7020CMD_TEMP_HOLD 0xE3 +/* Software Reset */ +#define SI7020CMD_RESET 0xFE + +static int si7020_read_raw(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, int *val, + int *val2, long mask) +{ + struct i2c_client **client = iio_priv(indio_dev); + int ret; + + switch (mask) { + case IIO_CHAN_INFO_RAW: + ret = i2c_smbus_read_word_swapped(*client, + chan->type == IIO_TEMP ? + SI7020CMD_TEMP_HOLD : + SI7020CMD_RH_HOLD); + if (ret < 0) + return ret; + *val = ret >> 2; + /* + * Humidity values can slightly exceed the 0-100%RH + * range and should be corrected by software + */ + if (chan->type == IIO_HUMIDITYRELATIVE) + *val = clamp_val(*val, 786, 13893); + return IIO_VAL_INT; + case IIO_CHAN_INFO_SCALE: + if (chan->type == IIO_TEMP) + *val = 175720; /* = 175.72 * 1000 */ + else + *val = 125 * 1000; + *val2 = 65536 >> 2; + return IIO_VAL_FRACTIONAL; + case IIO_CHAN_INFO_OFFSET: + /* + * Since iio_convert_raw_to_processed_unlocked assumes offset + * is an integer we have to round these values and lose + * accuracy. + * Relative humidity will be 0.0032959% too high and + * temperature will be 0.00277344 degrees too high. + * This is no big deal because it's within the accuracy of the + * sensor. + */ + if (chan->type == IIO_TEMP) + *val = -4368; /* = -46.85 * (65536 >> 2) / 175.72 */ + else + *val = -786; /* = -6 * (65536 >> 2) / 125 */ + return IIO_VAL_INT; + default: + break; + } + + return -EINVAL; +} + +static const struct iio_chan_spec si7020_channels[] = { + { + .type = IIO_HUMIDITYRELATIVE, + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | + BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET), + }, + { + .type = IIO_TEMP, + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | + BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET), + } +}; + +static const struct iio_info si7020_info = { + .read_raw = si7020_read_raw, +}; + +static int si7020_probe(struct i2c_client *client, + const struct i2c_device_id *id) +{ + struct iio_dev *indio_dev; + struct i2c_client **data; + int ret; + + if (!i2c_check_functionality(client->adapter, + I2C_FUNC_SMBUS_WRITE_BYTE | + I2C_FUNC_SMBUS_READ_WORD_DATA)) + return -EOPNOTSUPP; + + /* Reset device, loads default settings. */ + ret = i2c_smbus_write_byte(client, SI7020CMD_RESET); + if (ret < 0) + return ret; + /* Wait the maximum power-up time after software reset. */ + msleep(15); + + indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data)); + if (!indio_dev) + return -ENOMEM; + + data = iio_priv(indio_dev); + *data = client; + + indio_dev->dev.parent = &client->dev; + indio_dev->name = dev_name(&client->dev); + indio_dev->modes = INDIO_DIRECT_MODE; + indio_dev->info = &si7020_info; + indio_dev->channels = si7020_channels; + indio_dev->num_channels = ARRAY_SIZE(si7020_channels); + + return devm_iio_device_register(&client->dev, indio_dev); +} + +static const struct i2c_device_id si7020_id[] = { + { "si7020", 0 }, + { "th06", 0 }, + { } +}; +MODULE_DEVICE_TABLE(i2c, si7020_id); + +static const struct of_device_id si7020_dt_ids[] = { + { .compatible = "silabs,si7020" }, + { } +}; +MODULE_DEVICE_TABLE(of, si7020_dt_ids); + +static struct i2c_driver si7020_driver = { + .driver = { + .name = "si7020", + .of_match_table = of_match_ptr(si7020_dt_ids), + }, + .probe = si7020_probe, + .id_table = si7020_id, +}; + +module_i2c_driver(si7020_driver); +MODULE_DESCRIPTION("Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors"); +MODULE_AUTHOR("David Barksdale <dbarksdale@uplogix.com>"); +MODULE_LICENSE("GPL"); |