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5bf1d290 CM |
1 | /* Copyright (c) 2010 Christoph Mair <christoph.mair@gmail.com> |
2 | ||
3 | This driver supports the bmp085 digital barometric pressure | |
4 | and temperature sensor from Bosch Sensortec. The datasheet | |
25985edc | 5 | is available from their website: |
5bf1d290 CM |
6 | http://www.bosch-sensortec.com/content/language1/downloads/BST-BMP085-DS000-05.pdf |
7 | ||
8 | A pressure measurement is issued by reading from pressure0_input. | |
9 | The return value ranges from 30000 to 110000 pascal with a resulution | |
10 | of 1 pascal (0.01 millibar) which enables measurements from 9000m above | |
11 | to 500m below sea level. | |
12 | ||
13 | The temperature can be read from temp0_input. Values range from | |
14 | -400 to 850 representing the ambient temperature in degree celsius | |
15 | multiplied by 10.The resolution is 0.1 celsius. | |
16 | ||
17 | Because ambient pressure is temperature dependent, a temperature | |
18 | measurement will be executed automatically even if the user is reading | |
19 | from pressure0_input. This happens if the last temperature measurement | |
20 | has been executed more then one second ago. | |
21 | ||
22 | To decrease RMS noise from pressure measurements, the bmp085 can | |
23 | autonomously calculate the average of up to eight samples. This is | |
24 | set up by writing to the oversampling sysfs file. Accepted values | |
25 | are 0, 1, 2 and 3. 2^x when x is the value written to this file | |
26 | specifies the number of samples used to calculate the ambient pressure. | |
27 | RMS noise is specified with six pascal (without averaging) and decreases | |
28 | down to 3 pascal when using an oversampling setting of 3. | |
29 | ||
30 | This program is free software; you can redistribute it and/or modify | |
31 | it under the terms of the GNU General Public License as published by | |
32 | the Free Software Foundation; either version 2 of the License, or | |
33 | (at your option) any later version. | |
34 | ||
35 | This program is distributed in the hope that it will be useful, | |
36 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
37 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
38 | GNU General Public License for more details. | |
39 | ||
40 | You should have received a copy of the GNU General Public License | |
41 | along with this program; if not, write to the Free Software | |
42 | Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. | |
43 | */ | |
44 | ||
45 | ||
46 | #include <linux/module.h> | |
47 | #include <linux/init.h> | |
48 | #include <linux/i2c.h> | |
49 | #include <linux/slab.h> | |
50 | #include <linux/delay.h> | |
51 | ||
52 | ||
53 | #define BMP085_I2C_ADDRESS 0x77 | |
54 | #define BMP085_CHIP_ID 0x55 | |
55 | ||
56 | #define BMP085_CALIBRATION_DATA_START 0xAA | |
57 | #define BMP085_CALIBRATION_DATA_LENGTH 11 /* 16 bit values */ | |
58 | #define BMP085_CHIP_ID_REG 0xD0 | |
59 | #define BMP085_VERSION_REG 0xD1 | |
60 | #define BMP085_CTRL_REG 0xF4 | |
61 | #define BMP085_TEMP_MEASUREMENT 0x2E | |
62 | #define BMP085_PRESSURE_MEASUREMENT 0x34 | |
63 | #define BMP085_CONVERSION_REGISTER_MSB 0xF6 | |
64 | #define BMP085_CONVERSION_REGISTER_LSB 0xF7 | |
65 | #define BMP085_CONVERSION_REGISTER_XLSB 0xF8 | |
66 | #define BMP085_TEMP_CONVERSION_TIME 5 | |
67 | ||
68 | #define BMP085_CLIENT_NAME "bmp085" | |
69 | ||
70 | ||
71 | static const unsigned short normal_i2c[] = { BMP085_I2C_ADDRESS, | |
72 | I2C_CLIENT_END }; | |
73 | ||
74 | struct bmp085_calibration_data { | |
75 | s16 AC1, AC2, AC3; | |
76 | u16 AC4, AC5, AC6; | |
77 | s16 B1, B2; | |
78 | s16 MB, MC, MD; | |
79 | }; | |
80 | ||
81 | ||
82 | /* Each client has this additional data */ | |
83 | struct bmp085_data { | |
84 | struct i2c_client *client; | |
85 | struct mutex lock; | |
86 | struct bmp085_calibration_data calibration; | |
87 | u32 raw_temperature; | |
88 | u32 raw_pressure; | |
89 | unsigned char oversampling_setting; | |
b222258a | 90 | unsigned long last_temp_measurement; |
5bf1d290 CM |
91 | s32 b6; /* calculated temperature correction coefficient */ |
92 | }; | |
93 | ||
94 | ||
95 | static s32 bmp085_read_calibration_data(struct i2c_client *client) | |
96 | { | |
97 | u16 tmp[BMP085_CALIBRATION_DATA_LENGTH]; | |
98 | struct bmp085_data *data = i2c_get_clientdata(client); | |
99 | struct bmp085_calibration_data *cali = &(data->calibration); | |
100 | s32 status = i2c_smbus_read_i2c_block_data(client, | |
101 | BMP085_CALIBRATION_DATA_START, | |
102 | BMP085_CALIBRATION_DATA_LENGTH*sizeof(u16), | |
103 | (u8 *)tmp); | |
104 | if (status < 0) | |
105 | return status; | |
106 | ||
107 | if (status != BMP085_CALIBRATION_DATA_LENGTH*sizeof(u16)) | |
108 | return -EIO; | |
109 | ||
110 | cali->AC1 = be16_to_cpu(tmp[0]); | |
111 | cali->AC2 = be16_to_cpu(tmp[1]); | |
112 | cali->AC3 = be16_to_cpu(tmp[2]); | |
113 | cali->AC4 = be16_to_cpu(tmp[3]); | |
114 | cali->AC5 = be16_to_cpu(tmp[4]); | |
115 | cali->AC6 = be16_to_cpu(tmp[5]); | |
116 | cali->B1 = be16_to_cpu(tmp[6]); | |
117 | cali->B2 = be16_to_cpu(tmp[7]); | |
118 | cali->MB = be16_to_cpu(tmp[8]); | |
119 | cali->MC = be16_to_cpu(tmp[9]); | |
120 | cali->MD = be16_to_cpu(tmp[10]); | |
121 | return 0; | |
122 | } | |
123 | ||
124 | ||
125 | static s32 bmp085_update_raw_temperature(struct bmp085_data *data) | |
126 | { | |
127 | u16 tmp; | |
128 | s32 status; | |
129 | ||
130 | mutex_lock(&data->lock); | |
131 | status = i2c_smbus_write_byte_data(data->client, BMP085_CTRL_REG, | |
132 | BMP085_TEMP_MEASUREMENT); | |
133 | if (status != 0) { | |
134 | dev_err(&data->client->dev, | |
135 | "Error while requesting temperature measurement.\n"); | |
136 | goto exit; | |
137 | } | |
138 | msleep(BMP085_TEMP_CONVERSION_TIME); | |
139 | ||
140 | status = i2c_smbus_read_i2c_block_data(data->client, | |
141 | BMP085_CONVERSION_REGISTER_MSB, sizeof(tmp), (u8 *)&tmp); | |
142 | if (status < 0) | |
143 | goto exit; | |
144 | if (status != sizeof(tmp)) { | |
145 | dev_err(&data->client->dev, | |
146 | "Error while reading temperature measurement result\n"); | |
147 | status = -EIO; | |
148 | goto exit; | |
149 | } | |
150 | data->raw_temperature = be16_to_cpu(tmp); | |
151 | data->last_temp_measurement = jiffies; | |
152 | status = 0; /* everything ok, return 0 */ | |
153 | ||
154 | exit: | |
155 | mutex_unlock(&data->lock); | |
156 | return status; | |
157 | } | |
158 | ||
159 | static s32 bmp085_update_raw_pressure(struct bmp085_data *data) | |
160 | { | |
161 | u32 tmp = 0; | |
162 | s32 status; | |
163 | ||
164 | mutex_lock(&data->lock); | |
165 | status = i2c_smbus_write_byte_data(data->client, BMP085_CTRL_REG, | |
166 | BMP085_PRESSURE_MEASUREMENT + (data->oversampling_setting<<6)); | |
167 | if (status != 0) { | |
168 | dev_err(&data->client->dev, | |
169 | "Error while requesting pressure measurement.\n"); | |
170 | goto exit; | |
171 | } | |
172 | ||
173 | /* wait for the end of conversion */ | |
174 | msleep(2+(3 << data->oversampling_setting)); | |
175 | ||
176 | /* copy data into a u32 (4 bytes), but skip the first byte. */ | |
177 | status = i2c_smbus_read_i2c_block_data(data->client, | |
178 | BMP085_CONVERSION_REGISTER_MSB, 3, ((u8 *)&tmp)+1); | |
179 | if (status < 0) | |
180 | goto exit; | |
181 | if (status != 3) { | |
182 | dev_err(&data->client->dev, | |
183 | "Error while reading pressure measurement results\n"); | |
184 | status = -EIO; | |
185 | goto exit; | |
186 | } | |
187 | data->raw_pressure = be32_to_cpu((tmp)); | |
188 | data->raw_pressure >>= (8-data->oversampling_setting); | |
189 | status = 0; /* everything ok, return 0 */ | |
190 | ||
191 | exit: | |
192 | mutex_unlock(&data->lock); | |
193 | return status; | |
194 | } | |
195 | ||
196 | ||
197 | /* | |
198 | * This function starts the temperature measurement and returns the value | |
199 | * in tenth of a degree celsius. | |
200 | */ | |
201 | static s32 bmp085_get_temperature(struct bmp085_data *data, int *temperature) | |
202 | { | |
203 | struct bmp085_calibration_data *cali = &data->calibration; | |
204 | long x1, x2; | |
205 | int status; | |
206 | ||
207 | status = bmp085_update_raw_temperature(data); | |
208 | if (status != 0) | |
209 | goto exit; | |
210 | ||
211 | x1 = ((data->raw_temperature - cali->AC6) * cali->AC5) >> 15; | |
212 | x2 = (cali->MC << 11) / (x1 + cali->MD); | |
213 | data->b6 = x1 + x2 - 4000; | |
214 | /* if NULL just update b6. Used for pressure only measurements */ | |
215 | if (temperature != NULL) | |
216 | *temperature = (x1+x2+8) >> 4; | |
217 | ||
218 | exit: | |
f80ea668 | 219 | return status; |
5bf1d290 CM |
220 | } |
221 | ||
222 | /* | |
223 | * This function starts the pressure measurement and returns the value | |
224 | * in millibar. Since the pressure depends on the ambient temperature, | |
225 | * a temperature measurement is executed if the last known value is older | |
226 | * than one second. | |
227 | */ | |
228 | static s32 bmp085_get_pressure(struct bmp085_data *data, int *pressure) | |
229 | { | |
230 | struct bmp085_calibration_data *cali = &data->calibration; | |
231 | s32 x1, x2, x3, b3; | |
232 | u32 b4, b7; | |
233 | s32 p; | |
234 | int status; | |
235 | ||
236 | /* alt least every second force an update of the ambient temperature */ | |
3734f785 BW |
237 | if (data->last_temp_measurement == 0 || |
238 | time_is_before_jiffies(data->last_temp_measurement + 1*HZ)) { | |
5bf1d290 CM |
239 | status = bmp085_get_temperature(data, NULL); |
240 | if (status != 0) | |
241 | goto exit; | |
242 | } | |
243 | ||
244 | status = bmp085_update_raw_pressure(data); | |
245 | if (status != 0) | |
246 | goto exit; | |
247 | ||
248 | x1 = (data->b6 * data->b6) >> 12; | |
249 | x1 *= cali->B2; | |
250 | x1 >>= 11; | |
251 | ||
252 | x2 = cali->AC2 * data->b6; | |
253 | x2 >>= 11; | |
254 | ||
255 | x3 = x1 + x2; | |
256 | ||
257 | b3 = (((((s32)cali->AC1) * 4 + x3) << data->oversampling_setting) + 2); | |
258 | b3 >>= 2; | |
259 | ||
260 | x1 = (cali->AC3 * data->b6) >> 13; | |
261 | x2 = (cali->B1 * ((data->b6 * data->b6) >> 12)) >> 16; | |
262 | x3 = (x1 + x2 + 2) >> 2; | |
263 | b4 = (cali->AC4 * (u32)(x3 + 32768)) >> 15; | |
264 | ||
265 | b7 = ((u32)data->raw_pressure - b3) * | |
266 | (50000 >> data->oversampling_setting); | |
267 | p = ((b7 < 0x80000000) ? ((b7 << 1) / b4) : ((b7 / b4) * 2)); | |
268 | ||
269 | x1 = p >> 8; | |
270 | x1 *= x1; | |
271 | x1 = (x1 * 3038) >> 16; | |
272 | x2 = (-7357 * p) >> 16; | |
273 | p += (x1 + x2 + 3791) >> 4; | |
274 | ||
275 | *pressure = p; | |
276 | ||
277 | exit: | |
278 | return status; | |
279 | } | |
280 | ||
281 | /* | |
282 | * This function sets the chip-internal oversampling. Valid values are 0..3. | |
283 | * The chip will use 2^oversampling samples for internal averaging. | |
284 | * This influences the measurement time and the accuracy; larger values | |
285 | * increase both. The datasheet gives on overview on how measurement time, | |
286 | * accuracy and noise correlate. | |
287 | */ | |
288 | static void bmp085_set_oversampling(struct bmp085_data *data, | |
289 | unsigned char oversampling) | |
290 | { | |
291 | if (oversampling > 3) | |
292 | oversampling = 3; | |
293 | data->oversampling_setting = oversampling; | |
294 | } | |
295 | ||
296 | /* | |
297 | * Returns the currently selected oversampling. Range: 0..3 | |
298 | */ | |
299 | static unsigned char bmp085_get_oversampling(struct bmp085_data *data) | |
300 | { | |
301 | return data->oversampling_setting; | |
302 | } | |
303 | ||
304 | /* sysfs callbacks */ | |
305 | static ssize_t set_oversampling(struct device *dev, | |
306 | struct device_attribute *attr, | |
307 | const char *buf, size_t count) | |
308 | { | |
309 | struct i2c_client *client = to_i2c_client(dev); | |
310 | struct bmp085_data *data = i2c_get_clientdata(client); | |
311 | unsigned long oversampling; | |
312 | int success = strict_strtoul(buf, 10, &oversampling); | |
313 | if (success == 0) { | |
314 | bmp085_set_oversampling(data, oversampling); | |
315 | return count; | |
316 | } | |
317 | return success; | |
318 | } | |
319 | ||
320 | static ssize_t show_oversampling(struct device *dev, | |
321 | struct device_attribute *attr, char *buf) | |
322 | { | |
323 | struct i2c_client *client = to_i2c_client(dev); | |
324 | struct bmp085_data *data = i2c_get_clientdata(client); | |
325 | return sprintf(buf, "%u\n", bmp085_get_oversampling(data)); | |
326 | } | |
327 | static DEVICE_ATTR(oversampling, S_IWUSR | S_IRUGO, | |
328 | show_oversampling, set_oversampling); | |
329 | ||
330 | ||
331 | static ssize_t show_temperature(struct device *dev, | |
332 | struct device_attribute *attr, char *buf) | |
333 | { | |
334 | int temperature; | |
335 | int status; | |
336 | struct i2c_client *client = to_i2c_client(dev); | |
337 | struct bmp085_data *data = i2c_get_clientdata(client); | |
338 | ||
339 | status = bmp085_get_temperature(data, &temperature); | |
340 | if (status != 0) | |
341 | return status; | |
342 | else | |
343 | return sprintf(buf, "%d\n", temperature); | |
344 | } | |
345 | static DEVICE_ATTR(temp0_input, S_IRUGO, show_temperature, NULL); | |
346 | ||
347 | ||
348 | static ssize_t show_pressure(struct device *dev, | |
349 | struct device_attribute *attr, char *buf) | |
350 | { | |
351 | int pressure; | |
352 | int status; | |
353 | struct i2c_client *client = to_i2c_client(dev); | |
354 | struct bmp085_data *data = i2c_get_clientdata(client); | |
355 | ||
356 | status = bmp085_get_pressure(data, &pressure); | |
357 | if (status != 0) | |
358 | return status; | |
359 | else | |
360 | return sprintf(buf, "%d\n", pressure); | |
361 | } | |
362 | static DEVICE_ATTR(pressure0_input, S_IRUGO, show_pressure, NULL); | |
363 | ||
364 | ||
365 | static struct attribute *bmp085_attributes[] = { | |
366 | &dev_attr_temp0_input.attr, | |
367 | &dev_attr_pressure0_input.attr, | |
368 | &dev_attr_oversampling.attr, | |
369 | NULL | |
370 | }; | |
371 | ||
372 | static const struct attribute_group bmp085_attr_group = { | |
373 | .attrs = bmp085_attributes, | |
374 | }; | |
375 | ||
376 | static int bmp085_detect(struct i2c_client *client, struct i2c_board_info *info) | |
377 | { | |
378 | if (client->addr != BMP085_I2C_ADDRESS) | |
379 | return -ENODEV; | |
380 | ||
381 | if (i2c_smbus_read_byte_data(client, BMP085_CHIP_ID_REG) != BMP085_CHIP_ID) | |
382 | return -ENODEV; | |
383 | ||
384 | return 0; | |
385 | } | |
386 | ||
387 | static int bmp085_init_client(struct i2c_client *client) | |
388 | { | |
389 | unsigned char version; | |
390 | int status; | |
391 | struct bmp085_data *data = i2c_get_clientdata(client); | |
392 | data->client = client; | |
393 | status = bmp085_read_calibration_data(client); | |
394 | if (status != 0) | |
395 | goto exit; | |
396 | version = i2c_smbus_read_byte_data(client, BMP085_VERSION_REG); | |
397 | data->last_temp_measurement = 0; | |
398 | data->oversampling_setting = 3; | |
399 | mutex_init(&data->lock); | |
400 | dev_info(&data->client->dev, "BMP085 ver. %d.%d found.\n", | |
401 | (version & 0x0F), (version & 0xF0) >> 4); | |
402 | exit: | |
403 | return status; | |
404 | } | |
405 | ||
45bff2ea | 406 | static int __devinit bmp085_probe(struct i2c_client *client, |
5bf1d290 CM |
407 | const struct i2c_device_id *id) |
408 | { | |
409 | struct bmp085_data *data; | |
410 | int err = 0; | |
411 | ||
412 | data = kzalloc(sizeof(struct bmp085_data), GFP_KERNEL); | |
413 | if (!data) { | |
414 | err = -ENOMEM; | |
415 | goto exit; | |
416 | } | |
417 | ||
418 | /* default settings after POR */ | |
419 | data->oversampling_setting = 0x00; | |
420 | ||
421 | i2c_set_clientdata(client, data); | |
422 | ||
423 | /* Initialize the BMP085 chip */ | |
424 | err = bmp085_init_client(client); | |
425 | if (err != 0) | |
426 | goto exit_free; | |
427 | ||
428 | /* Register sysfs hooks */ | |
429 | err = sysfs_create_group(&client->dev.kobj, &bmp085_attr_group); | |
430 | if (err) | |
431 | goto exit_free; | |
432 | ||
25985edc | 433 | dev_info(&data->client->dev, "Successfully initialized bmp085!\n"); |
5bf1d290 CM |
434 | goto exit; |
435 | ||
436 | exit_free: | |
437 | kfree(data); | |
438 | exit: | |
439 | return err; | |
440 | } | |
441 | ||
45bff2ea | 442 | static int __devexit bmp085_remove(struct i2c_client *client) |
5bf1d290 CM |
443 | { |
444 | sysfs_remove_group(&client->dev.kobj, &bmp085_attr_group); | |
445 | kfree(i2c_get_clientdata(client)); | |
446 | return 0; | |
447 | } | |
448 | ||
449 | static const struct i2c_device_id bmp085_id[] = { | |
450 | { "bmp085", 0 }, | |
451 | { } | |
452 | }; | |
97e419a0 | 453 | MODULE_DEVICE_TABLE(i2c, bmp085_id); |
5bf1d290 CM |
454 | |
455 | static struct i2c_driver bmp085_driver = { | |
456 | .driver = { | |
457 | .owner = THIS_MODULE, | |
458 | .name = "bmp085" | |
459 | }, | |
460 | .id_table = bmp085_id, | |
461 | .probe = bmp085_probe, | |
45bff2ea | 462 | .remove = __devexit_p(bmp085_remove), |
5bf1d290 CM |
463 | |
464 | .detect = bmp085_detect, | |
465 | .address_list = normal_i2c | |
466 | }; | |
467 | ||
a64fe2ed | 468 | module_i2c_driver(bmp085_driver); |
5bf1d290 CM |
469 | |
470 | MODULE_AUTHOR("Christoph Mair <christoph.mair@gmail.com"); | |
471 | MODULE_DESCRIPTION("BMP085 driver"); | |
472 | MODULE_LICENSE("GPL"); |