1 // SPDX-License-Identifier: GPL-2.0-only
4 * aht10.c - Linux hwmon driver for AHT10/AHT20 Temperature and Humidity sensors
5 * Copyright (C) 2020 Johannes Cornelis Draaijer
8 #include <linux/delay.h>
9 #include <linux/hwmon.h>
10 #include <linux/i2c.h>
11 #include <linux/ktime.h>
12 #include <linux/module.h>
13 #include <linux/crc8.h>
15 #define AHT10_MEAS_SIZE 6
17 #define AHT20_MEAS_SIZE 7
18 #define AHT20_CRC8_POLY 0x31
21 * Poll intervals (in milliseconds)
23 #define AHT10_DEFAULT_MIN_POLL_INTERVAL 2000
24 #define AHT10_MIN_POLL_INTERVAL 2000
27 * I2C command delays (in microseconds)
29 #define AHT10_MEAS_DELAY 80000
30 #define AHT10_CMD_DELAY 350000
31 #define AHT10_DELAY_EXTRA 100000
36 #define AHT10_CMD_INIT 0b11100001
37 #define AHT10_CMD_MEAS 0b10101100
38 #define AHT10_CMD_RST 0b10111010
41 * Flags in the answer byte/command
43 #define AHT10_CAL_ENABLED BIT(3)
44 #define AHT10_BUSY BIT(7)
45 #define AHT10_MODE_NOR (BIT(5) | BIT(6))
46 #define AHT10_MODE_CYC BIT(5)
47 #define AHT10_MODE_CMD BIT(6)
49 #define AHT10_MAX_POLL_INTERVAL_LEN 30
51 enum aht10_variant { aht10, aht20 };
53 static const struct i2c_device_id aht10_id[] = {
58 MODULE_DEVICE_TABLE(i2c, aht10_id);
60 static const struct of_device_id aht10_of_id[] = {
61 { .compatible = "aosong,aht10", },
64 MODULE_DEVICE_TABLE(of, aht10_of_id);
67 * struct aht10_data - All the data required to operate an AHT10/AHT20 chip
68 * @client: the i2c client associated with the AHT10/AHT20
69 * @lock: a mutex that is used to prevent parallel access to the
71 * @min_poll_interval: the minimum poll interval
72 * While the poll rate limit is not 100% necessary,
73 * the datasheet recommends that a measurement
74 * is not performed too often to prevent
75 * the chip from warming up due to the heat it generates.
76 * If it's unwanted, it can be ignored setting it to
77 * it to 0. Default value is 2000 ms
78 * @previous_poll_time: the previous time that the AHT10/AHT20
80 * @temperature: the latest temperature value received from
82 * @humidity: the latest humidity value received from the
84 * @crc8: crc8 support flag
85 * @meas_size: measurements data size
89 struct i2c_client *client;
91 * Prevent simultaneous access to the i2c
92 * client and previous_poll_time
95 ktime_t min_poll_interval;
96 ktime_t previous_poll_time;
100 unsigned int meas_size;
104 * aht10_init() - Initialize an AHT10/AHT20 chip
105 * @data: the data associated with this AHT10/AHT20 chip
106 * Return: 0 if successful, 1 if not
108 static int aht10_init(struct aht10_data *data)
110 const u8 cmd_init[] = {AHT10_CMD_INIT, AHT10_CAL_ENABLED | AHT10_MODE_CYC,
114 struct i2c_client *client = data->client;
116 res = i2c_master_send(client, cmd_init, 3);
120 usleep_range(AHT10_CMD_DELAY, AHT10_CMD_DELAY +
123 res = i2c_master_recv(client, &status, 1);
127 if (status & AHT10_BUSY)
134 * aht10_polltime_expired() - check if the minimum poll interval has
136 * @data: the data containing the time to compare
137 * Return: 1 if the minimum poll interval has expired, 0 if not
139 static int aht10_polltime_expired(struct aht10_data *data)
141 ktime_t current_time = ktime_get_boottime();
142 ktime_t difference = ktime_sub(current_time, data->previous_poll_time);
144 return ktime_after(difference, data->min_poll_interval);
147 DECLARE_CRC8_TABLE(crc8_table);
150 * crc8_check() - check crc of the sensor's measurements
151 * @raw_data: data frame received from sensor(including crc as the last byte)
152 * @count: size of the data frame
153 * Return: 0 if successful, 1 if not
155 static int crc8_check(u8 *raw_data, int count)
158 * crc calculated on the whole frame(including crc byte) should yield
159 * zero in case of correctly received bytes
161 return crc8(crc8_table, raw_data, count, CRC8_INIT_VALUE);
165 * aht10_read_values() - read and parse the raw data from the AHT10/AHT20
166 * @data: the struct aht10_data to use for the lock
167 * Return: 0 if successful, 1 if not
169 static int aht10_read_values(struct aht10_data *data)
171 const u8 cmd_meas[] = {AHT10_CMD_MEAS, 0x33, 0x00};
174 u8 raw_data[AHT20_MEAS_SIZE];
175 struct i2c_client *client = data->client;
177 mutex_lock(&data->lock);
178 if (!aht10_polltime_expired(data)) {
179 mutex_unlock(&data->lock);
183 res = i2c_master_send(client, cmd_meas, sizeof(cmd_meas));
185 mutex_unlock(&data->lock);
189 usleep_range(AHT10_MEAS_DELAY, AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA);
191 res = i2c_master_recv(client, raw_data, data->meas_size);
192 if (res != data->meas_size) {
193 mutex_unlock(&data->lock);
199 if (data->crc8 && crc8_check(raw_data, data->meas_size)) {
200 mutex_unlock(&data->lock);
204 hum = ((u32)raw_data[1] << 12u) |
205 ((u32)raw_data[2] << 4u) |
206 ((raw_data[3] & 0xF0u) >> 4u);
208 temp = ((u32)(raw_data[3] & 0x0Fu) << 16u) |
209 ((u32)raw_data[4] << 8u) |
212 temp = ((temp * 625) >> 15u) * 10;
213 hum = ((hum * 625) >> 16u) * 10;
215 data->temperature = (int)temp - 50000;
216 data->humidity = hum;
217 data->previous_poll_time = ktime_get_boottime();
219 mutex_unlock(&data->lock);
224 * aht10_interval_write() - store the given minimum poll interval.
225 * Return: 0 on success, -EINVAL if a value lower than the
226 * AHT10_MIN_POLL_INTERVAL is given
228 static ssize_t aht10_interval_write(struct aht10_data *data,
231 data->min_poll_interval = ms_to_ktime(clamp_val(val, 2000, LONG_MAX));
236 * aht10_interval_read() - read the minimum poll interval
239 static ssize_t aht10_interval_read(struct aht10_data *data,
242 *val = ktime_to_ms(data->min_poll_interval);
247 * aht10_temperature1_read() - read the temperature in millidegrees
249 static int aht10_temperature1_read(struct aht10_data *data, long *val)
253 res = aht10_read_values(data);
257 *val = data->temperature;
262 * aht10_humidity1_read() - read the relative humidity in millipercent
264 static int aht10_humidity1_read(struct aht10_data *data, long *val)
268 res = aht10_read_values(data);
272 *val = data->humidity;
276 static umode_t aht10_hwmon_visible(const void *data, enum hwmon_sensor_types type,
277 u32 attr, int channel)
290 static int aht10_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
291 u32 attr, int channel, long *val)
293 struct aht10_data *data = dev_get_drvdata(dev);
297 return aht10_temperature1_read(data, val);
299 return aht10_humidity1_read(data, val);
301 return aht10_interval_read(data, val);
307 static int aht10_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
308 u32 attr, int channel, long val)
310 struct aht10_data *data = dev_get_drvdata(dev);
314 return aht10_interval_write(data, val);
320 static const struct hwmon_channel_info * const aht10_info[] = {
321 HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL),
322 HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
323 HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT),
327 static const struct hwmon_ops aht10_hwmon_ops = {
328 .is_visible = aht10_hwmon_visible,
329 .read = aht10_hwmon_read,
330 .write = aht10_hwmon_write,
333 static const struct hwmon_chip_info aht10_chip_info = {
334 .ops = &aht10_hwmon_ops,
338 static int aht10_probe(struct i2c_client *client)
340 const struct i2c_device_id *id = i2c_match_id(aht10_id, client);
341 enum aht10_variant variant = id->driver_data;
342 struct device *device = &client->dev;
343 struct device *hwmon_dev;
344 struct aht10_data *data;
347 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
350 data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL);
354 data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL);
355 data->client = client;
359 data->meas_size = AHT20_MEAS_SIZE;
361 crc8_populate_msb(crc8_table, AHT20_CRC8_POLY);
364 data->meas_size = AHT10_MEAS_SIZE;
368 mutex_init(&data->lock);
370 res = aht10_init(data);
374 res = aht10_read_values(data);
378 hwmon_dev = devm_hwmon_device_register_with_info(device,
384 return PTR_ERR_OR_ZERO(hwmon_dev);
387 static struct i2c_driver aht10_driver = {
390 .of_match_table = aht10_of_id,
392 .probe = aht10_probe,
393 .id_table = aht10_id,
396 module_i2c_driver(aht10_driver);
398 MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>");
399 MODULE_DESCRIPTION("AHT10/AHT20 Temperature and Humidity sensor driver");
400 MODULE_VERSION("1.0");
401 MODULE_LICENSE("GPL v2");