2 * Aosong AM2315 relative humidity and temperature
4 * Copyright (c) 2016, Intel Corporation.
6 * This file is subject to the terms and conditions of version 2 of
7 * the GNU General Public License. See the file COPYING in the main
8 * directory of this archive for more details.
10 * 7-bit I2C address: 0x5C.
13 #include <linux/acpi.h>
14 #include <linux/delay.h>
15 #include <linux/i2c.h>
16 #include <linux/kernel.h>
17 #include <linux/module.h>
18 #include <linux/iio/buffer.h>
19 #include <linux/iio/iio.h>
20 #include <linux/iio/sysfs.h>
21 #include <linux/iio/trigger_consumer.h>
22 #include <linux/iio/triggered_buffer.h>
24 #define AM2315_REG_HUM_MSB 0x00
25 #define AM2315_REG_HUM_LSB 0x01
26 #define AM2315_REG_TEMP_MSB 0x02
27 #define AM2315_REG_TEMP_LSB 0x03
29 #define AM2315_FUNCTION_READ 0x03
30 #define AM2315_HUM_OFFSET 2
31 #define AM2315_TEMP_OFFSET 4
32 #define AM2315_ALL_CHANNEL_MASK GENMASK(1, 0)
34 #define AM2315_DRIVER_NAME "am2315"
37 struct i2c_client *client;
39 /* Ensure timestamp is naturally aligned */
42 s64 timestamp __aligned(8);
46 struct am2315_sensor_data {
51 static const struct iio_chan_spec am2315_channels[] = {
53 .type = IIO_HUMIDITYRELATIVE,
54 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
55 BIT(IIO_CHAN_INFO_SCALE),
61 .endianness = IIO_CPU,
66 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
67 BIT(IIO_CHAN_INFO_SCALE),
73 .endianness = IIO_CPU,
76 IIO_CHAN_SOFT_TIMESTAMP(2),
79 /* CRC calculation algorithm, as specified in the datasheet (page 13). */
80 static u16 am2315_crc(u8 *data, u8 nr_bytes)
87 for (i = 0; i < 8; i++) {
100 /* Simple function that sends a few bytes to the device to wake it up. */
101 static void am2315_ping(struct i2c_client *client)
103 i2c_smbus_read_byte_data(client, AM2315_REG_HUM_MSB);
106 static int am2315_read_data(struct am2315_data *data,
107 struct am2315_sensor_data *sensor_data)
110 /* tx_buf format: <function code> <start addr> <nr of regs to read> */
111 u8 tx_buf[3] = { AM2315_FUNCTION_READ, AM2315_REG_HUM_MSB, 4 };
114 * <function code> <number of registers read>
115 * <humidity MSB> <humidity LSB> <temp MSB> <temp LSB>
116 * <CRC LSB> <CRC MSB>
121 /* First wake up the device. */
122 am2315_ping(data->client);
124 mutex_lock(&data->lock);
125 ret = i2c_master_send(data->client, tx_buf, sizeof(tx_buf));
127 dev_err(&data->client->dev, "failed to send read request\n");
130 /* Wait 2-3 ms, then read back the data sent by the device. */
131 usleep_range(2000, 3000);
132 /* Do a bulk data read, then pick out what we need. */
133 ret = i2c_master_recv(data->client, rx_buf, sizeof(rx_buf));
135 dev_err(&data->client->dev, "failed to read sensor data\n");
138 mutex_unlock(&data->lock);
140 * Do a CRC check on the data and compare it to the value
141 * calculated by the device.
143 crc = am2315_crc(rx_buf, sizeof(rx_buf) - 2);
144 if ((crc & 0xff) != rx_buf[6] || (crc >> 8) != rx_buf[7]) {
145 dev_err(&data->client->dev, "failed to verify sensor data\n");
149 sensor_data->hum_data = (rx_buf[AM2315_HUM_OFFSET] << 8) |
150 rx_buf[AM2315_HUM_OFFSET + 1];
151 sensor_data->temp_data = (rx_buf[AM2315_TEMP_OFFSET] << 8) |
152 rx_buf[AM2315_TEMP_OFFSET + 1];
157 mutex_unlock(&data->lock);
161 static irqreturn_t am2315_trigger_handler(int irq, void *p)
166 struct iio_poll_func *pf = p;
167 struct iio_dev *indio_dev = pf->indio_dev;
168 struct am2315_data *data = iio_priv(indio_dev);
169 struct am2315_sensor_data sensor_data;
171 ret = am2315_read_data(data, &sensor_data);
175 mutex_lock(&data->lock);
176 if (*(indio_dev->active_scan_mask) == AM2315_ALL_CHANNEL_MASK) {
177 data->scan.chans[0] = sensor_data.hum_data;
178 data->scan.chans[1] = sensor_data.temp_data;
181 for_each_set_bit(bit, indio_dev->active_scan_mask,
182 indio_dev->masklength) {
183 data->scan.chans[i] = (bit ? sensor_data.temp_data :
184 sensor_data.hum_data);
188 mutex_unlock(&data->lock);
190 iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
193 iio_trigger_notify_done(indio_dev->trig);
197 static int am2315_read_raw(struct iio_dev *indio_dev,
198 struct iio_chan_spec const *chan,
199 int *val, int *val2, long mask)
202 struct am2315_sensor_data sensor_data;
203 struct am2315_data *data = iio_priv(indio_dev);
206 case IIO_CHAN_INFO_RAW:
207 ret = am2315_read_data(data, &sensor_data);
210 *val = (chan->type == IIO_HUMIDITYRELATIVE) ?
211 sensor_data.hum_data : sensor_data.temp_data;
213 case IIO_CHAN_INFO_SCALE:
221 static const struct iio_info am2315_info = {
222 .driver_module = THIS_MODULE,
223 .read_raw = am2315_read_raw,
226 static int am2315_probe(struct i2c_client *client,
227 const struct i2c_device_id *id)
230 struct iio_dev *indio_dev;
231 struct am2315_data *data;
233 indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
235 dev_err(&client->dev, "iio allocation failed!\n");
239 data = iio_priv(indio_dev);
240 data->client = client;
241 i2c_set_clientdata(client, indio_dev);
242 mutex_init(&data->lock);
244 indio_dev->dev.parent = &client->dev;
245 indio_dev->info = &am2315_info;
246 indio_dev->name = AM2315_DRIVER_NAME;
247 indio_dev->modes = INDIO_DIRECT_MODE;
248 indio_dev->channels = am2315_channels;
249 indio_dev->num_channels = ARRAY_SIZE(am2315_channels);
251 ret = iio_triggered_buffer_setup(indio_dev, iio_pollfunc_store_time,
252 am2315_trigger_handler, NULL);
254 dev_err(&client->dev, "iio triggered buffer setup failed\n");
258 ret = iio_device_register(indio_dev);
260 goto err_buffer_cleanup;
265 iio_triggered_buffer_cleanup(indio_dev);
269 static int am2315_remove(struct i2c_client *client)
271 struct iio_dev *indio_dev = i2c_get_clientdata(client);
273 iio_device_unregister(indio_dev);
274 iio_triggered_buffer_cleanup(indio_dev);
279 static const struct i2c_device_id am2315_i2c_id[] = {
283 MODULE_DEVICE_TABLE(i2c, am2315_i2c_id);
285 static const struct acpi_device_id am2315_acpi_id[] = {
290 MODULE_DEVICE_TABLE(acpi, am2315_acpi_id);
292 static struct i2c_driver am2315_driver = {
295 .acpi_match_table = ACPI_PTR(am2315_acpi_id),
297 .probe = am2315_probe,
298 .remove = am2315_remove,
299 .id_table = am2315_i2c_id,
302 module_i2c_driver(am2315_driver);
304 MODULE_AUTHOR("Tiberiu Breana <tiberiu.a.breana@intel.com>");
305 MODULE_DESCRIPTION("Aosong AM2315 relative humidity and temperature");
306 MODULE_LICENSE("GPL v2");