linux/drivers/iio/chemical/ccs811.c
Richard Lai 4c73b809a9 iio: chemical: ccs811: Renamed resistance member in ccs811_reading struct
The resistance member in ccs811_reading struct is an unsigned 16-bit
integer variable used to store RAW_DATA register bytes read from CCS811.
It is kind of misleading to name this struct member as resistance.

About the RAW_DATA register bytes, the CCS811 datasheet states that:
-----
Two byte read only register which contains the latest readings from the
sense resistor.

The most significant 6 bits of the Byte 0 contain the value of the current
through the sensor (0μA to 63μA).

The lower 10 bits contain (as computed from the ADC) the readings of the
voltage across the sensor with the selected current (1023 = 1.65V)"
-----

Hence, the RAW_DATA register byte contains information about electric
current and voltage of the CCS811 sensor. Calling this struct member
'resistance' is kind of misleading, although both electric current and
voltage are needed to calculate the electrical resistance of the sensor
using Ohm's law, V = I x R, in which a new channel type of IIO_RESISTANCE
may be added to the driver in the future.

Signed-off-by: Richard Lai <richard@richardman.com>

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
2018-02-24 11:04:28 +00:00

482 lines
12 KiB
C

/*
* ccs811.c - Support for AMS CCS811 VOC Sensor
*
* Copyright (C) 2017 Narcisa Vasile <narcisaanamaria12@gmail.com>
*
* Datasheet: ams.com/content/download/951091/2269479/CCS811_DS000459_3-00.pdf
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* IIO driver for AMS CCS811 (I2C address 0x5A/0x5B set by ADDR Low/High)
*
* TODO:
* 1. Make the drive mode selectable form userspace
* 2. Add support for interrupts
* 3. Adjust time to wait for data to be ready based on selected operation mode
* 4. Read error register and put the information in logs
*/
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/iio/iio.h>
#include <linux/iio/buffer.h>
#include <linux/iio/trigger.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/iio/trigger_consumer.h>
#include <linux/module.h>
#define CCS811_STATUS 0x00
#define CCS811_MEAS_MODE 0x01
#define CCS811_ALG_RESULT_DATA 0x02
#define CCS811_RAW_DATA 0x03
#define CCS811_HW_ID 0x20
#define CCS811_HW_ID_VALUE 0x81
#define CCS811_HW_VERSION 0x21
#define CCS811_HW_VERSION_VALUE 0x10
#define CCS811_HW_VERSION_MASK 0xF0
#define CCS811_ERR 0xE0
/* Used to transition from boot to application mode */
#define CCS811_APP_START 0xF4
/* Status register flags */
#define CCS811_STATUS_ERROR BIT(0)
#define CCS811_STATUS_DATA_READY BIT(3)
#define CCS811_STATUS_APP_VALID_MASK BIT(4)
#define CCS811_STATUS_APP_VALID_LOADED BIT(4)
/*
* Value of FW_MODE bit of STATUS register describes the sensor's state:
* 0: Firmware is in boot mode, this allows new firmware to be loaded
* 1: Firmware is in application mode. CCS811 is ready to take ADC measurements
*/
#define CCS811_STATUS_FW_MODE_MASK BIT(7)
#define CCS811_STATUS_FW_MODE_APPLICATION BIT(7)
/* Measurement modes */
#define CCS811_MODE_IDLE 0x00
#define CCS811_MODE_IAQ_1SEC 0x10
#define CCS811_MODE_IAQ_10SEC 0x20
#define CCS811_MODE_IAQ_60SEC 0x30
#define CCS811_MODE_RAW_DATA 0x40
#define CCS811_MEAS_MODE_INTERRUPT BIT(3)
#define CCS811_VOLTAGE_MASK 0x3FF
struct ccs811_reading {
__be16 co2;
__be16 voc;
u8 status;
u8 error;
__be16 raw_data;
} __attribute__((__packed__));
struct ccs811_data {
struct i2c_client *client;
struct mutex lock; /* Protect readings */
struct ccs811_reading buffer;
struct iio_trigger *drdy_trig;
bool drdy_trig_on;
};
static const struct iio_chan_spec ccs811_channels[] = {
{
.type = IIO_CURRENT,
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
BIT(IIO_CHAN_INFO_SCALE),
.scan_index = -1,
}, {
.type = IIO_VOLTAGE,
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
BIT(IIO_CHAN_INFO_SCALE),
.scan_index = -1,
}, {
.type = IIO_CONCENTRATION,
.channel2 = IIO_MOD_CO2,
.modified = 1,
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
BIT(IIO_CHAN_INFO_SCALE),
.scan_index = 0,
.scan_type = {
.sign = 'u',
.realbits = 16,
.storagebits = 16,
.endianness = IIO_BE,
},
}, {
.type = IIO_CONCENTRATION,
.channel2 = IIO_MOD_VOC,
.modified = 1,
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
BIT(IIO_CHAN_INFO_SCALE),
.scan_index = 1,
.scan_type = {
.sign = 'u',
.realbits = 16,
.storagebits = 16,
.endianness = IIO_BE,
},
},
IIO_CHAN_SOFT_TIMESTAMP(2),
};
/*
* The CCS811 powers-up in boot mode. A setup write to CCS811_APP_START will
* transition the sensor to application mode.
*/
static int ccs811_start_sensor_application(struct i2c_client *client)
{
int ret;
ret = i2c_smbus_read_byte_data(client, CCS811_STATUS);
if (ret < 0)
return ret;
if ((ret & CCS811_STATUS_APP_VALID_MASK) !=
CCS811_STATUS_APP_VALID_LOADED)
return -EIO;
ret = i2c_smbus_write_byte(client, CCS811_APP_START);
if (ret < 0)
return ret;
ret = i2c_smbus_read_byte_data(client, CCS811_STATUS);
if (ret < 0)
return ret;
if ((ret & CCS811_STATUS_FW_MODE_MASK) !=
CCS811_STATUS_FW_MODE_APPLICATION) {
dev_err(&client->dev, "Application failed to start. Sensor is still in boot mode.\n");
return -EIO;
}
return 0;
}
static int ccs811_setup(struct i2c_client *client)
{
int ret;
ret = ccs811_start_sensor_application(client);
if (ret < 0)
return ret;
return i2c_smbus_write_byte_data(client, CCS811_MEAS_MODE,
CCS811_MODE_IAQ_1SEC);
}
static int ccs811_get_measurement(struct ccs811_data *data)
{
int ret, tries = 11;
/* Maximum waiting time: 1s, as measurements are made every second */
while (tries-- > 0) {
ret = i2c_smbus_read_byte_data(data->client, CCS811_STATUS);
if (ret < 0)
return ret;
if ((ret & CCS811_STATUS_DATA_READY) || tries == 0)
break;
msleep(100);
}
if (!(ret & CCS811_STATUS_DATA_READY))
return -EIO;
return i2c_smbus_read_i2c_block_data(data->client,
CCS811_ALG_RESULT_DATA, 8,
(char *)&data->buffer);
}
static int ccs811_read_raw(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
int *val, int *val2, long mask)
{
struct ccs811_data *data = iio_priv(indio_dev);
int ret;
switch (mask) {
case IIO_CHAN_INFO_RAW:
ret = iio_device_claim_direct_mode(indio_dev);
if (ret)
return ret;
mutex_lock(&data->lock);
ret = ccs811_get_measurement(data);
if (ret < 0) {
mutex_unlock(&data->lock);
iio_device_release_direct_mode(indio_dev);
return ret;
}
switch (chan->type) {
case IIO_VOLTAGE:
*val = be16_to_cpu(data->buffer.raw_data) &
CCS811_VOLTAGE_MASK;
ret = IIO_VAL_INT;
break;
case IIO_CURRENT:
*val = be16_to_cpu(data->buffer.raw_data) >> 10;
ret = IIO_VAL_INT;
break;
case IIO_CONCENTRATION:
switch (chan->channel2) {
case IIO_MOD_CO2:
*val = be16_to_cpu(data->buffer.co2);
ret = IIO_VAL_INT;
break;
case IIO_MOD_VOC:
*val = be16_to_cpu(data->buffer.voc);
ret = IIO_VAL_INT;
break;
default:
ret = -EINVAL;
}
break;
default:
ret = -EINVAL;
}
mutex_unlock(&data->lock);
iio_device_release_direct_mode(indio_dev);
return ret;
case IIO_CHAN_INFO_SCALE:
switch (chan->type) {
case IIO_VOLTAGE:
*val = 1;
*val2 = 612903;
return IIO_VAL_INT_PLUS_MICRO;
case IIO_CURRENT:
*val = 0;
*val2 = 1000;
return IIO_VAL_INT_PLUS_MICRO;
case IIO_CONCENTRATION:
switch (chan->channel2) {
case IIO_MOD_CO2:
*val = 0;
*val2 = 100;
return IIO_VAL_INT_PLUS_MICRO;
case IIO_MOD_VOC:
*val = 0;
*val2 = 100;
return IIO_VAL_INT_PLUS_NANO;
default:
return -EINVAL;
}
default:
return -EINVAL;
}
default:
return -EINVAL;
}
}
static const struct iio_info ccs811_info = {
.read_raw = ccs811_read_raw,
};
static int ccs811_set_trigger_state(struct iio_trigger *trig,
bool state)
{
struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
struct ccs811_data *data = iio_priv(indio_dev);
int ret;
ret = i2c_smbus_read_byte_data(data->client, CCS811_MEAS_MODE);
if (ret < 0)
return ret;
if (state)
ret |= CCS811_MEAS_MODE_INTERRUPT;
else
ret &= ~CCS811_MEAS_MODE_INTERRUPT;
data->drdy_trig_on = state;
return i2c_smbus_write_byte_data(data->client, CCS811_MEAS_MODE, ret);
}
static const struct iio_trigger_ops ccs811_trigger_ops = {
.set_trigger_state = ccs811_set_trigger_state,
};
static irqreturn_t ccs811_trigger_handler(int irq, void *p)
{
struct iio_poll_func *pf = p;
struct iio_dev *indio_dev = pf->indio_dev;
struct ccs811_data *data = iio_priv(indio_dev);
struct i2c_client *client = data->client;
s16 buf[8]; /* s16 eCO2 + s16 TVOC + padding + 8 byte timestamp */
int ret;
ret = i2c_smbus_read_i2c_block_data(client, CCS811_ALG_RESULT_DATA, 4,
(u8 *)&buf);
if (ret != 4) {
dev_err(&client->dev, "cannot read sensor data\n");
goto err;
}
iio_push_to_buffers_with_timestamp(indio_dev, buf,
iio_get_time_ns(indio_dev));
err:
iio_trigger_notify_done(indio_dev->trig);
return IRQ_HANDLED;
}
static irqreturn_t ccs811_data_rdy_trigger_poll(int irq, void *private)
{
struct iio_dev *indio_dev = private;
struct ccs811_data *data = iio_priv(indio_dev);
if (data->drdy_trig_on)
iio_trigger_poll(data->drdy_trig);
return IRQ_HANDLED;
}
static int ccs811_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct iio_dev *indio_dev;
struct ccs811_data *data;
int ret;
if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WRITE_BYTE
| I2C_FUNC_SMBUS_BYTE_DATA
| I2C_FUNC_SMBUS_READ_I2C_BLOCK))
return -EOPNOTSUPP;
/* Check hardware id (should be 0x81 for this family of devices) */
ret = i2c_smbus_read_byte_data(client, CCS811_HW_ID);
if (ret < 0)
return ret;
if (ret != CCS811_HW_ID_VALUE) {
dev_err(&client->dev, "hardware id doesn't match CCS81x\n");
return -ENODEV;
}
ret = i2c_smbus_read_byte_data(client, CCS811_HW_VERSION);
if (ret < 0)
return ret;
if ((ret & CCS811_HW_VERSION_MASK) != CCS811_HW_VERSION_VALUE) {
dev_err(&client->dev, "no CCS811 sensor\n");
return -ENODEV;
}
indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
if (!indio_dev)
return -ENOMEM;
ret = ccs811_setup(client);
if (ret < 0)
return ret;
data = iio_priv(indio_dev);
i2c_set_clientdata(client, indio_dev);
data->client = client;
mutex_init(&data->lock);
indio_dev->dev.parent = &client->dev;
indio_dev->name = id->name;
indio_dev->info = &ccs811_info;
indio_dev->modes = INDIO_DIRECT_MODE;
indio_dev->channels = ccs811_channels;
indio_dev->num_channels = ARRAY_SIZE(ccs811_channels);
if (client->irq > 0) {
ret = devm_request_threaded_irq(&client->dev, client->irq,
ccs811_data_rdy_trigger_poll,
NULL,
IRQF_TRIGGER_FALLING |
IRQF_ONESHOT,
"ccs811_irq", indio_dev);
if (ret) {
dev_err(&client->dev, "irq request error %d\n", -ret);
goto err_poweroff;
}
data->drdy_trig = devm_iio_trigger_alloc(&client->dev,
"%s-dev%d",
indio_dev->name,
indio_dev->id);
if (!data->drdy_trig) {
ret = -ENOMEM;
goto err_poweroff;
}
data->drdy_trig->dev.parent = &client->dev;
data->drdy_trig->ops = &ccs811_trigger_ops;
iio_trigger_set_drvdata(data->drdy_trig, indio_dev);
indio_dev->trig = data->drdy_trig;
iio_trigger_get(indio_dev->trig);
ret = iio_trigger_register(data->drdy_trig);
if (ret)
goto err_poweroff;
}
ret = iio_triggered_buffer_setup(indio_dev, NULL,
ccs811_trigger_handler, NULL);
if (ret < 0) {
dev_err(&client->dev, "triggered buffer setup failed\n");
goto err_trigger_unregister;
}
ret = iio_device_register(indio_dev);
if (ret < 0) {
dev_err(&client->dev, "unable to register iio device\n");
goto err_buffer_cleanup;
}
return 0;
err_buffer_cleanup:
iio_triggered_buffer_cleanup(indio_dev);
err_trigger_unregister:
if (data->drdy_trig)
iio_trigger_unregister(data->drdy_trig);
err_poweroff:
i2c_smbus_write_byte_data(client, CCS811_MEAS_MODE, CCS811_MODE_IDLE);
return ret;
}
static int ccs811_remove(struct i2c_client *client)
{
struct iio_dev *indio_dev = i2c_get_clientdata(client);
struct ccs811_data *data = iio_priv(indio_dev);
iio_device_unregister(indio_dev);
iio_triggered_buffer_cleanup(indio_dev);
if (data->drdy_trig)
iio_trigger_unregister(data->drdy_trig);
return i2c_smbus_write_byte_data(client, CCS811_MEAS_MODE,
CCS811_MODE_IDLE);
}
static const struct i2c_device_id ccs811_id[] = {
{"ccs811", 0},
{ }
};
MODULE_DEVICE_TABLE(i2c, ccs811_id);
static struct i2c_driver ccs811_driver = {
.driver = {
.name = "ccs811",
},
.probe = ccs811_probe,
.remove = ccs811_remove,
.id_table = ccs811_id,
};
module_i2c_driver(ccs811_driver);
MODULE_AUTHOR("Narcisa Vasile <narcisaanamaria12@gmail.com>");
MODULE_DESCRIPTION("CCS811 volatile organic compounds sensor");
MODULE_LICENSE("GPL v2");