LXR linux/drivers/iio/humidity/si7020.c

   1/*
   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>
   5 *
   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.
   9 *
  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.
  14 */
  15
  16/*
  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.
  21 *
  22 * Data Sheets:
  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
  26 */
  27
  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>
  33
  34#include <linux/iio/iio.h>
  35#include <linux/iio/sysfs.h>
  36
  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
  41/* Software Reset */
  42#define SI7020CMD_RESET         0xFE
  43
  44static int si7020_read_raw(struct iio_dev *indio_dev,
  45                           struct iio_chan_spec const *chan, int *val,
  46                           int *val2, long mask)
  47{
  48        struct i2c_client **client = iio_priv(indio_dev);
  49        int ret;
  50
  51        switch (mask) {
  52        case IIO_CHAN_INFO_RAW:
  53                ret = i2c_smbus_read_word_swapped(*client,
  54                                                  chan->type == IIO_TEMP ?
  55                                                  SI7020CMD_TEMP_HOLD :
  56                                                  SI7020CMD_RH_HOLD);
  57                if (ret < 0)
  58                        return ret;
  59                *val = ret >> 2;
  60                /*
  61                 * Humidity values can slightly exceed the 0-100%RH
  62                 * range and should be corrected by software
  63                 */
  64                if (chan->type == IIO_HUMIDITYRELATIVE)
  65                        *val = clamp_val(*val, 786, 13893);
  66                return IIO_VAL_INT;
  67        case IIO_CHAN_INFO_SCALE:
  68                if (chan->type == IIO_TEMP)
  69                        *val = 175720; /* = 175.72 * 1000 */
  70                else
  71                        *val = 125 * 1000;
  72                *val2 = 65536 >> 2;
  73                return IIO_VAL_FRACTIONAL;
  74        case IIO_CHAN_INFO_OFFSET:
  75                /*
  76                 * Since iio_convert_raw_to_processed_unlocked assumes offset
  77                 * is an integer we have to round these values and lose
  78                 * accuracy.
  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
  82                 * sensor.
  83                 */
  84                if (chan->type == IIO_TEMP)
  85                        *val = -4368; /* = -46.85 * (65536 >> 2) / 175.72 */
  86                else
  87                        *val = -786; /* = -6 * (65536 >> 2) / 125 */
  88                return IIO_VAL_INT;
  89        default:
  90                break;
  91        }
  92
  93        return -EINVAL;
  94}
  95
  96static const struct iio_chan_spec si7020_channels[] = {
  97        {
  98                .type = IIO_HUMIDITYRELATIVE,
  99                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
 100                        BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
 101        },
 102        {
 103                .type = IIO_TEMP,
 104                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
 105                        BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
 106        }
 107};
 108
 109static const struct iio_info si7020_info = {
 110        .read_raw = si7020_read_raw,
 111        .driver_module = THIS_MODULE,
 112};
 113
 114static int si7020_probe(struct i2c_client *client,
 115                        const struct i2c_device_id *id)
 116{
 117        struct iio_dev *indio_dev;
 118        struct i2c_client **data;
 119        int ret;
 120
 121        if (!i2c_check_functionality(client->adapter,
 122                                     I2C_FUNC_SMBUS_WRITE_BYTE |
 123                                     I2C_FUNC_SMBUS_READ_WORD_DATA))
 124                return -EOPNOTSUPP;
 125
 126        /* Reset device, loads default settings. */
 127        ret = i2c_smbus_write_byte(client, SI7020CMD_RESET);
 128        if (ret < 0)
 129                return ret;
 130        /* Wait the maximum power-up time after software reset. */
 131        msleep(15);
 132
 133        indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
 134        if (!indio_dev)
 135                return -ENOMEM;
 136
 137        data = iio_priv(indio_dev);
 138        *data = client;
 139
 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);
 146
 147        return devm_iio_device_register(&client->dev, indio_dev);
 148}
 149
 150static const struct i2c_device_id si7020_id[] = {
 151        { "si7020", 0 },
 152        { "th06", 0 },
 153        { }
 154};
 155MODULE_DEVICE_TABLE(i2c, si7020_id);
 156
 157static struct i2c_driver si7020_driver = {
 158        .driver.name    = "si7020",
 159        .probe          = si7020_probe,
 160        .id_table       = si7020_id,
 161};
 162
 163module_i2c_driver(si7020_driver);
 164MODULE_DESCRIPTION("Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors");
 165MODULE_AUTHOR("David Barksdale <dbarksdale@uplogix.com>");
 166MODULE_LICENSE("GPL");
 167