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430400b8 UF |
1 | /* Sensirion SHT21 humidity and temperature sensor driver |
2 | * | |
3 | * Copyright (C) 2010 Urs Fleisch <urs.fleisch@sensirion.com> | |
4 | * | |
5 | * This program is free software; you can redistribute it and/or modify | |
6 | * it under the terms of the GNU General Public License as published by | |
7 | * the Free Software Foundation; either version 2 of the License, or | |
8 | * (at your option) any later version. | |
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 | * You should have received a copy of the GNU General Public License | |
16 | * along with this program; if not, write to the Free Software | |
17 | * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA | |
18 | * | |
19 | * Data sheet available (5/2010) at | |
20 | * http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT21.pdf | |
21 | */ | |
22 | ||
23 | #include <linux/module.h> | |
24 | #include <linux/init.h> | |
25 | #include <linux/slab.h> | |
26 | #include <linux/i2c.h> | |
27 | #include <linux/hwmon.h> | |
28 | #include <linux/hwmon-sysfs.h> | |
29 | #include <linux/err.h> | |
30 | #include <linux/mutex.h> | |
31 | #include <linux/device.h> | |
dcd8f392 | 32 | #include <linux/jiffies.h> |
430400b8 UF |
33 | |
34 | /* I2C command bytes */ | |
35 | #define SHT21_TRIG_T_MEASUREMENT_HM 0xe3 | |
36 | #define SHT21_TRIG_RH_MEASUREMENT_HM 0xe5 | |
53e678d7 PB |
37 | #define SHT21_READ_SNB_CMD1 0xFA |
38 | #define SHT21_READ_SNB_CMD2 0x0F | |
39 | #define SHT21_READ_SNAC_CMD1 0xFC | |
40 | #define SHT21_READ_SNAC_CMD2 0xC9 | |
430400b8 UF |
41 | |
42 | /** | |
43 | * struct sht21 - SHT21 device specific data | |
44 | * @hwmon_dev: device registered with hwmon | |
45 | * @lock: mutex to protect measurement values | |
430400b8 UF |
46 | * @last_update: time of last update (jiffies) |
47 | * @temperature: cached temperature measurement value | |
48 | * @humidity: cached humidity measurement value | |
53e678d7 PB |
49 | * @valid: only 0 before first measurement is taken |
50 | * @eic: cached electronic identification code text | |
430400b8 UF |
51 | */ |
52 | struct sht21 { | |
b8d56898 | 53 | struct i2c_client *client; |
430400b8 | 54 | struct mutex lock; |
430400b8 UF |
55 | unsigned long last_update; |
56 | int temperature; | |
57 | int humidity; | |
53e678d7 PB |
58 | char valid; |
59 | char eic[18]; | |
430400b8 UF |
60 | }; |
61 | ||
62 | /** | |
63 | * sht21_temp_ticks_to_millicelsius() - convert raw temperature ticks to | |
64 | * milli celsius | |
65 | * @ticks: temperature ticks value received from sensor | |
66 | */ | |
67 | static inline int sht21_temp_ticks_to_millicelsius(int ticks) | |
68 | { | |
69 | ticks &= ~0x0003; /* clear status bits */ | |
70 | /* | |
71 | * Formula T = -46.85 + 175.72 * ST / 2^16 from data sheet 6.2, | |
72 | * optimized for integer fixed point (3 digits) arithmetic | |
73 | */ | |
74 | return ((21965 * ticks) >> 13) - 46850; | |
75 | } | |
76 | ||
77 | /** | |
78 | * sht21_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to | |
79 | * one-thousandths of a percent relative humidity | |
80 | * @ticks: humidity ticks value received from sensor | |
81 | */ | |
82 | static inline int sht21_rh_ticks_to_per_cent_mille(int ticks) | |
83 | { | |
84 | ticks &= ~0x0003; /* clear status bits */ | |
85 | /* | |
86 | * Formula RH = -6 + 125 * SRH / 2^16 from data sheet 6.1, | |
87 | * optimized for integer fixed point (3 digits) arithmetic | |
88 | */ | |
89 | return ((15625 * ticks) >> 13) - 6000; | |
90 | } | |
91 | ||
430400b8 UF |
92 | /** |
93 | * sht21_update_measurements() - get updated measurements from device | |
b8d56898 | 94 | * @dev: device |
430400b8 UF |
95 | * |
96 | * Returns 0 on success, else negative errno. | |
97 | */ | |
b8d56898 | 98 | static int sht21_update_measurements(struct device *dev) |
430400b8 UF |
99 | { |
100 | int ret = 0; | |
b8d56898 AL |
101 | struct sht21 *sht21 = dev_get_drvdata(dev); |
102 | struct i2c_client *client = sht21->client; | |
430400b8 UF |
103 | |
104 | mutex_lock(&sht21->lock); | |
105 | /* | |
106 | * Data sheet 2.4: | |
107 | * SHT2x should not be active for more than 10% of the time - e.g. | |
108 | * maximum two measurements per second at 12bit accuracy shall be made. | |
109 | */ | |
110 | if (time_after(jiffies, sht21->last_update + HZ / 2) || !sht21->valid) { | |
90f4102c JD |
111 | ret = i2c_smbus_read_word_swapped(client, |
112 | SHT21_TRIG_T_MEASUREMENT_HM); | |
430400b8 UF |
113 | if (ret < 0) |
114 | goto out; | |
115 | sht21->temperature = sht21_temp_ticks_to_millicelsius(ret); | |
90f4102c JD |
116 | ret = i2c_smbus_read_word_swapped(client, |
117 | SHT21_TRIG_RH_MEASUREMENT_HM); | |
430400b8 UF |
118 | if (ret < 0) |
119 | goto out; | |
120 | sht21->humidity = sht21_rh_ticks_to_per_cent_mille(ret); | |
121 | sht21->last_update = jiffies; | |
122 | sht21->valid = 1; | |
123 | } | |
124 | out: | |
125 | mutex_unlock(&sht21->lock); | |
126 | ||
127 | return ret >= 0 ? 0 : ret; | |
128 | } | |
129 | ||
130 | /** | |
131 | * sht21_show_temperature() - show temperature measurement value in sysfs | |
132 | * @dev: device | |
133 | * @attr: device attribute | |
134 | * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to | |
135 | * | |
136 | * Will be called on read access to temp1_input sysfs attribute. | |
137 | * Returns number of bytes written into buffer, negative errno on error. | |
138 | */ | |
139 | static ssize_t sht21_show_temperature(struct device *dev, | |
140 | struct device_attribute *attr, | |
141 | char *buf) | |
142 | { | |
b8d56898 AL |
143 | struct sht21 *sht21 = dev_get_drvdata(dev); |
144 | int ret; | |
145 | ||
146 | ret = sht21_update_measurements(dev); | |
430400b8 UF |
147 | if (ret < 0) |
148 | return ret; | |
149 | return sprintf(buf, "%d\n", sht21->temperature); | |
150 | } | |
151 | ||
152 | /** | |
153 | * sht21_show_humidity() - show humidity measurement value in sysfs | |
154 | * @dev: device | |
155 | * @attr: device attribute | |
156 | * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to | |
157 | * | |
158 | * Will be called on read access to humidity1_input sysfs attribute. | |
159 | * Returns number of bytes written into buffer, negative errno on error. | |
160 | */ | |
161 | static ssize_t sht21_show_humidity(struct device *dev, | |
162 | struct device_attribute *attr, | |
163 | char *buf) | |
164 | { | |
b8d56898 AL |
165 | struct sht21 *sht21 = dev_get_drvdata(dev); |
166 | int ret; | |
167 | ||
168 | ret = sht21_update_measurements(dev); | |
430400b8 UF |
169 | if (ret < 0) |
170 | return ret; | |
171 | return sprintf(buf, "%d\n", sht21->humidity); | |
172 | } | |
173 | ||
53e678d7 PB |
174 | static ssize_t eic_read(struct sht21 *sht21) |
175 | { | |
176 | struct i2c_client *client = sht21->client; | |
177 | u8 tx[2]; | |
178 | u8 rx[8]; | |
179 | u8 eic[8]; | |
180 | struct i2c_msg msgs[2] = { | |
181 | { | |
182 | .addr = client->addr, | |
183 | .flags = 0, | |
184 | .len = 2, | |
185 | .buf = tx, | |
186 | }, | |
187 | { | |
188 | .addr = client->addr, | |
189 | .flags = I2C_M_RD, | |
190 | .len = 8, | |
191 | .buf = rx, | |
192 | }, | |
193 | }; | |
194 | int ret; | |
195 | ||
196 | tx[0] = SHT21_READ_SNB_CMD1; | |
197 | tx[1] = SHT21_READ_SNB_CMD2; | |
198 | ret = i2c_transfer(client->adapter, msgs, 2); | |
199 | if (ret < 0) | |
200 | goto out; | |
201 | eic[2] = rx[0]; | |
202 | eic[3] = rx[2]; | |
203 | eic[4] = rx[4]; | |
204 | eic[5] = rx[6]; | |
205 | ||
206 | tx[0] = SHT21_READ_SNAC_CMD1; | |
207 | tx[1] = SHT21_READ_SNAC_CMD2; | |
208 | msgs[1].len = 6; | |
209 | ret = i2c_transfer(client->adapter, msgs, 2); | |
210 | if (ret < 0) | |
211 | goto out; | |
212 | eic[0] = rx[3]; | |
213 | eic[1] = rx[4]; | |
214 | eic[6] = rx[0]; | |
215 | eic[7] = rx[1]; | |
216 | ||
217 | ret = snprintf(sht21->eic, sizeof(sht21->eic), | |
218 | "%02x%02x%02x%02x%02x%02x%02x%02x\n", | |
219 | eic[0], eic[1], eic[2], eic[3], | |
220 | eic[4], eic[5], eic[6], eic[7]); | |
221 | out: | |
222 | if (ret < 0) | |
223 | sht21->eic[0] = 0; | |
224 | ||
225 | return ret; | |
226 | } | |
227 | ||
228 | /** | |
229 | * eic_show() - show Electronic Identification Code in sysfs | |
230 | * @dev: device | |
231 | * @attr: device attribute | |
232 | * @buf: sysfs buffer (PAGE_SIZE) where EIC is written | |
233 | * | |
234 | * Will be called on read access to eic sysfs attribute. | |
235 | * Returns number of bytes written into buffer, negative errno on error. | |
236 | */ | |
237 | static ssize_t eic_show(struct device *dev, | |
238 | struct device_attribute *attr, | |
239 | char *buf) | |
240 | { | |
241 | struct sht21 *sht21 = dev_get_drvdata(dev); | |
242 | int ret; | |
243 | ||
244 | ret = sizeof(sht21->eic) - 1; | |
245 | mutex_lock(&sht21->lock); | |
246 | if (!sht21->eic[0]) | |
247 | ret = eic_read(sht21); | |
248 | if (ret > 0) | |
249 | memcpy(buf, sht21->eic, ret); | |
250 | mutex_unlock(&sht21->lock); | |
251 | return ret; | |
252 | } | |
253 | ||
430400b8 UF |
254 | /* sysfs attributes */ |
255 | static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, sht21_show_temperature, | |
256 | NULL, 0); | |
257 | static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, sht21_show_humidity, | |
258 | NULL, 0); | |
53e678d7 | 259 | static DEVICE_ATTR_RO(eic); |
430400b8 | 260 | |
b8d56898 | 261 | static struct attribute *sht21_attrs[] = { |
430400b8 UF |
262 | &sensor_dev_attr_temp1_input.dev_attr.attr, |
263 | &sensor_dev_attr_humidity1_input.dev_attr.attr, | |
53e678d7 | 264 | &dev_attr_eic.attr, |
430400b8 UF |
265 | NULL |
266 | }; | |
267 | ||
b8d56898 | 268 | ATTRIBUTE_GROUPS(sht21); |
430400b8 | 269 | |
6c931ae1 | 270 | static int sht21_probe(struct i2c_client *client, |
430400b8 UF |
271 | const struct i2c_device_id *id) |
272 | { | |
b8d56898 AL |
273 | struct device *dev = &client->dev; |
274 | struct device *hwmon_dev; | |
430400b8 | 275 | struct sht21 *sht21; |
430400b8 UF |
276 | |
277 | if (!i2c_check_functionality(client->adapter, | |
278 | I2C_FUNC_SMBUS_WORD_DATA)) { | |
279 | dev_err(&client->dev, | |
280 | "adapter does not support SMBus word transactions\n"); | |
281 | return -ENODEV; | |
282 | } | |
283 | ||
b8d56898 | 284 | sht21 = devm_kzalloc(dev, sizeof(*sht21), GFP_KERNEL); |
a844af19 | 285 | if (!sht21) |
430400b8 | 286 | return -ENOMEM; |
a844af19 | 287 | |
b8d56898 | 288 | sht21->client = client; |
430400b8 UF |
289 | |
290 | mutex_init(&sht21->lock); | |
291 | ||
b8d56898 AL |
292 | hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name, |
293 | sht21, sht21_groups); | |
294 | return PTR_ERR_OR_ZERO(hwmon_dev); | |
430400b8 UF |
295 | } |
296 | ||
297 | /* Device ID table */ | |
298 | static const struct i2c_device_id sht21_id[] = { | |
299 | { "sht21", 0 }, | |
300 | { } | |
301 | }; | |
302 | MODULE_DEVICE_TABLE(i2c, sht21_id); | |
303 | ||
304 | static struct i2c_driver sht21_driver = { | |
305 | .driver.name = "sht21", | |
306 | .probe = sht21_probe, | |
430400b8 UF |
307 | .id_table = sht21_id, |
308 | }; | |
309 | ||
f0967eea | 310 | module_i2c_driver(sht21_driver); |
430400b8 UF |
311 | |
312 | MODULE_AUTHOR("Urs Fleisch <urs.fleisch@sensirion.com>"); | |
313 | MODULE_DESCRIPTION("Sensirion SHT21 humidity and temperature sensor driver"); | |
314 | MODULE_LICENSE("GPL"); |