2 * si7020.c - Silicon Labs Si7013/20/21 Relative Humidity and Temp Sensors
3 * Copyright (c) 2013,2014 Uplogix, Inc.
4 * David Barksdale <dbarksdale@uplogix.com>
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms and conditions of the GNU General Public License,
8 * version 2, as published by the Free Software Foundation.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
17 * The Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors
18 * are i2c devices which have an identical programming interface for
19 * measuring relative humidity and temperature. The Si7013 has an additional
20 * temperature input which this driver does not support.
23 * Si7013: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7013.pdf
24 * Si7020: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7020.pdf
25 * Si7021: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7021.pdf
28 #include <linux/delay.h>
29 #include <linux/i2c.h>
30 #include <linux/module.h>
31 #include <linux/slab.h>
32 #include <linux/sysfs.h>
34 #include <linux/iio/iio.h>
35 #include <linux/iio/sysfs.h>
37 /* Measure Relative Humidity, Hold Master Mode */
38 #define SI7020CMD_RH_HOLD 0xE5
39 /* Measure Temperature, Hold Master Mode */
40 #define SI7020CMD_TEMP_HOLD 0xE3
42 #define SI7020CMD_RESET 0xFE
44 static int si7020_read_raw(struct iio_dev *indio_dev,
45 struct iio_chan_spec const *chan, int *val,
48 struct i2c_client **client = iio_priv(indio_dev);
52 case IIO_CHAN_INFO_RAW:
53 ret = i2c_smbus_read_word_swapped(*client,
54 chan->type == IIO_TEMP ?
61 * Humidity values can slightly exceed the 0-100%RH
62 * range and should be corrected by software
64 if (chan->type == IIO_HUMIDITYRELATIVE)
65 *val = clamp_val(*val, 786, 13893);
67 case IIO_CHAN_INFO_SCALE:
68 if (chan->type == IIO_TEMP)
69 *val = 175720; /* = 175.72 * 1000 */
73 return IIO_VAL_FRACTIONAL;
74 case IIO_CHAN_INFO_OFFSET:
76 * Since iio_convert_raw_to_processed_unlocked assumes offset
77 * is an integer we have to round these values and lose
79 * Relative humidity will be 0.0032959% too high and
80 * temperature will be 0.00277344 degrees too high.
81 * This is no big deal because it's within the accuracy of the
84 if (chan->type == IIO_TEMP)
85 *val = -4368; /* = -46.85 * (65536 >> 2) / 175.72 */
87 *val = -786; /* = -6 * (65536 >> 2) / 125 */
96 static const struct iio_chan_spec si7020_channels[] = {
98 .type = IIO_HUMIDITYRELATIVE,
99 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
100 BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
104 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
105 BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
109 static const struct iio_info si7020_info = {
110 .read_raw = si7020_read_raw,
111 .driver_module = THIS_MODULE,
114 static int si7020_probe(struct i2c_client *client,
115 const struct i2c_device_id *id)
117 struct iio_dev *indio_dev;
118 struct i2c_client **data;
121 if (!i2c_check_functionality(client->adapter,
122 I2C_FUNC_SMBUS_WRITE_BYTE |
123 I2C_FUNC_SMBUS_READ_WORD_DATA))
126 /* Reset device, loads default settings. */
127 ret = i2c_smbus_write_byte(client, SI7020CMD_RESET);
130 /* Wait the maximum power-up time after software reset. */
133 indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
137 data = iio_priv(indio_dev);
140 indio_dev->dev.parent = &client->dev;
141 indio_dev->name = dev_name(&client->dev);
142 indio_dev->modes = INDIO_DIRECT_MODE;
143 indio_dev->info = &si7020_info;
144 indio_dev->channels = si7020_channels;
145 indio_dev->num_channels = ARRAY_SIZE(si7020_channels);
147 return devm_iio_device_register(&client->dev, indio_dev);
150 static const struct i2c_device_id si7020_id[] = {
155 MODULE_DEVICE_TABLE(i2c, si7020_id);
157 static const struct of_device_id si7020_dt_ids[] = {
158 { .compatible = "silabs,si7020" },
161 MODULE_DEVICE_TABLE(of, si7020_dt_ids);
163 static struct i2c_driver si7020_driver = {
166 .of_match_table = of_match_ptr(si7020_dt_ids),
168 .probe = si7020_probe,
169 .id_table = si7020_id,
172 module_i2c_driver(si7020_driver);
173 MODULE_DESCRIPTION("Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors");
174 MODULE_AUTHOR("David Barksdale <dbarksdale@uplogix.com>");
175 MODULE_LICENSE("GPL");