si7020.c
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/*
* 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,
.driver_module = THIS_MODULE,
};
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 -ENODEV;
/* 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 },
{ }
};
MODULE_DEVICE_TABLE(i2c, si7020_id);
static struct i2c_driver si7020_driver = {
.driver.name = "si7020",
.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");