diff options
author | Harald Geyer <harald@ccbib.org> | 2013-12-01 10:04:00 -0500 |
---|---|---|
committer | Jonathan Cameron <jic23@kernel.org> | 2013-12-03 15:22:30 -0500 |
commit | 091a121b04547fab2045951aff6219318ede0560 (patch) | |
tree | d6753de7cf21bdc8de3a62952ce79cd0adc060a1 /drivers/iio/humidity | |
parent | ac216aa290c48a5e9d7b9f2473abb977a175683a (diff) |
iio: Add new driver dht11
This driver handles DHT11 and DHT22 sensors.
Signed-off-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Diffstat (limited to 'drivers/iio/humidity')
-rw-r--r-- | drivers/iio/humidity/Kconfig | 15 | ||||
-rw-r--r-- | drivers/iio/humidity/Makefile | 5 | ||||
-rw-r--r-- | drivers/iio/humidity/dht11.c | 294 |
3 files changed, 314 insertions, 0 deletions
diff --git a/drivers/iio/humidity/Kconfig b/drivers/iio/humidity/Kconfig new file mode 100644 index 000000000000..463c4d9da79e --- /dev/null +++ b/drivers/iio/humidity/Kconfig | |||
@@ -0,0 +1,15 @@ | |||
1 | # | ||
2 | # humidity sensor drivers | ||
3 | # | ||
4 | menu "Humidity sensors" | ||
5 | |||
6 | config DHT11 | ||
7 | tristate "DHT11 (and compatible sensors) driver" | ||
8 | depends on GPIOLIB | ||
9 | help | ||
10 | This driver supports reading data via a single interrupt | ||
11 | generating GPIO line. Currently tested are DHT11 and DHT22. | ||
12 | Other sensors should work as well as long as they speak the | ||
13 | same protocol. | ||
14 | |||
15 | endmenu | ||
diff --git a/drivers/iio/humidity/Makefile b/drivers/iio/humidity/Makefile new file mode 100644 index 000000000000..d5d36c0c95f9 --- /dev/null +++ b/drivers/iio/humidity/Makefile | |||
@@ -0,0 +1,5 @@ | |||
1 | # | ||
2 | # Makefile for IIO humidity sensor drivers | ||
3 | # | ||
4 | |||
5 | obj-$(CONFIG_DHT11) += dht11.o | ||
diff --git a/drivers/iio/humidity/dht11.c b/drivers/iio/humidity/dht11.c new file mode 100644 index 000000000000..d8771f546bf2 --- /dev/null +++ b/drivers/iio/humidity/dht11.c | |||
@@ -0,0 +1,294 @@ | |||
1 | /* | ||
2 | * DHT11/DHT22 bit banging GPIO driver | ||
3 | * | ||
4 | * Copyright (c) Harald Geyer <harald@ccbib.org> | ||
5 | * | ||
6 | * This program is free software; you can redistribute it and/or modify | ||
7 | * it under the terms of the GNU General Public License as published by | ||
8 | * the Free Software Foundation; either version 2 of the License, or | ||
9 | * (at your option) any later version. | ||
10 | * | ||
11 | * This program is distributed in the hope that it will be useful, | ||
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
14 | * GNU General Public License for more details. | ||
15 | */ | ||
16 | |||
17 | #include <linux/err.h> | ||
18 | #include <linux/interrupt.h> | ||
19 | #include <linux/device.h> | ||
20 | #include <linux/kernel.h> | ||
21 | #include <linux/printk.h> | ||
22 | #include <linux/slab.h> | ||
23 | #include <linux/of.h> | ||
24 | #include <linux/of_device.h> | ||
25 | #include <linux/sysfs.h> | ||
26 | #include <linux/io.h> | ||
27 | #include <linux/module.h> | ||
28 | #include <linux/platform_device.h> | ||
29 | #include <linux/wait.h> | ||
30 | #include <linux/bitops.h> | ||
31 | #include <linux/completion.h> | ||
32 | #include <linux/delay.h> | ||
33 | #include <linux/gpio.h> | ||
34 | #include <linux/of_gpio.h> | ||
35 | |||
36 | #include <linux/iio/iio.h> | ||
37 | |||
38 | #define DRIVER_NAME "dht11" | ||
39 | |||
40 | #define DHT11_DATA_VALID_TIME 2000000000 /* 2s in ns */ | ||
41 | |||
42 | #define DHT11_EDGES_PREAMBLE 4 | ||
43 | #define DHT11_BITS_PER_READ 40 | ||
44 | #define DHT11_EDGES_PER_READ (2*DHT11_BITS_PER_READ + DHT11_EDGES_PREAMBLE + 1) | ||
45 | |||
46 | /* Data transmission timing (nano seconds) */ | ||
47 | #define DHT11_START_TRANSMISSION 18 /* ms */ | ||
48 | #define DHT11_SENSOR_RESPONSE 80000 | ||
49 | #define DHT11_START_BIT 50000 | ||
50 | #define DHT11_DATA_BIT_LOW 27000 | ||
51 | #define DHT11_DATA_BIT_HIGH 70000 | ||
52 | |||
53 | struct dht11 { | ||
54 | struct device *dev; | ||
55 | |||
56 | int gpio; | ||
57 | int irq; | ||
58 | |||
59 | struct completion completion; | ||
60 | |||
61 | s64 timestamp; | ||
62 | int temperature; | ||
63 | int humidity; | ||
64 | |||
65 | /* num_edges: -1 means "no transmission in progress" */ | ||
66 | int num_edges; | ||
67 | struct {s64 ts; int value; } edges[DHT11_EDGES_PER_READ]; | ||
68 | }; | ||
69 | |||
70 | static unsigned char dht11_decode_byte(int *timing, int threshold) | ||
71 | { | ||
72 | unsigned char ret = 0; | ||
73 | int i; | ||
74 | |||
75 | for (i = 0; i < 8; ++i) { | ||
76 | ret <<= 1; | ||
77 | if (timing[i] >= threshold) | ||
78 | ++ret; | ||
79 | } | ||
80 | |||
81 | return ret; | ||
82 | } | ||
83 | |||
84 | static int dht11_decode(struct dht11 *dht11, int offset) | ||
85 | { | ||
86 | int i, t, timing[DHT11_BITS_PER_READ], threshold, | ||
87 | timeres = DHT11_SENSOR_RESPONSE; | ||
88 | unsigned char temp_int, temp_dec, hum_int, hum_dec, checksum; | ||
89 | |||
90 | /* Calculate timestamp resolution */ | ||
91 | for (i = 0; i < dht11->num_edges; ++i) { | ||
92 | t = dht11->edges[i].ts - dht11->edges[i-1].ts; | ||
93 | if (t > 0 && t < timeres) | ||
94 | timeres = t; | ||
95 | } | ||
96 | if (2*timeres > DHT11_DATA_BIT_HIGH) { | ||
97 | pr_err("dht11: timeresolution %d too bad for decoding\n", | ||
98 | timeres); | ||
99 | return -EIO; | ||
100 | } | ||
101 | threshold = DHT11_DATA_BIT_HIGH / timeres; | ||
102 | if (DHT11_DATA_BIT_LOW/timeres + 1 >= threshold) | ||
103 | pr_err("dht11: WARNING: decoding ambiguous\n"); | ||
104 | |||
105 | /* scale down with timeres and check validity */ | ||
106 | for (i = 0; i < DHT11_BITS_PER_READ; ++i) { | ||
107 | t = dht11->edges[offset + 2*i + 2].ts - | ||
108 | dht11->edges[offset + 2*i + 1].ts; | ||
109 | if (!dht11->edges[offset + 2*i + 1].value) | ||
110 | return -EIO; /* lost synchronisation */ | ||
111 | timing[i] = t / timeres; | ||
112 | } | ||
113 | |||
114 | hum_int = dht11_decode_byte(timing, threshold); | ||
115 | hum_dec = dht11_decode_byte(&timing[8], threshold); | ||
116 | temp_int = dht11_decode_byte(&timing[16], threshold); | ||
117 | temp_dec = dht11_decode_byte(&timing[24], threshold); | ||
118 | checksum = dht11_decode_byte(&timing[32], threshold); | ||
119 | |||
120 | if (((hum_int + hum_dec + temp_int + temp_dec) & 0xff) != checksum) | ||
121 | return -EIO; | ||
122 | |||
123 | dht11->timestamp = iio_get_time_ns(); | ||
124 | if (hum_int < 20) { /* DHT22 */ | ||
125 | dht11->temperature = (((temp_int & 0x7f) << 8) + temp_dec) * | ||
126 | ((temp_int & 0x80) ? -100 : 100); | ||
127 | dht11->humidity = ((hum_int << 8) + hum_dec) * 100; | ||
128 | } else if (temp_dec == 0 && hum_dec == 0) { /* DHT11 */ | ||
129 | dht11->temperature = temp_int * 1000; | ||
130 | dht11->humidity = hum_int * 1000; | ||
131 | } else { | ||
132 | dev_err(dht11->dev, | ||
133 | "Don't know how to decode data: %d %d %d %d\n", | ||
134 | hum_int, hum_dec, temp_int, temp_dec); | ||
135 | return -EIO; | ||
136 | } | ||
137 | |||
138 | return 0; | ||
139 | } | ||
140 | |||
141 | static int dht11_read_raw(struct iio_dev *iio_dev, | ||
142 | const struct iio_chan_spec *chan, | ||
143 | int *val, int *val2, long m) | ||
144 | { | ||
145 | struct dht11 *dht11 = iio_priv(iio_dev); | ||
146 | int ret; | ||
147 | |||
148 | if (dht11->timestamp + DHT11_DATA_VALID_TIME < iio_get_time_ns()) { | ||
149 | reinit_completion(&dht11->completion); | ||
150 | |||
151 | dht11->num_edges = 0; | ||
152 | ret = gpio_direction_output(dht11->gpio, 0); | ||
153 | if (ret) | ||
154 | goto err; | ||
155 | msleep(DHT11_START_TRANSMISSION); | ||
156 | ret = gpio_direction_input(dht11->gpio); | ||
157 | if (ret) | ||
158 | goto err; | ||
159 | |||
160 | ret = wait_for_completion_killable_timeout(&dht11->completion, | ||
161 | HZ); | ||
162 | if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) { | ||
163 | dev_err(&iio_dev->dev, | ||
164 | "Only %d signal edges detected\n", | ||
165 | dht11->num_edges); | ||
166 | ret = -ETIMEDOUT; | ||
167 | } | ||
168 | if (ret < 0) | ||
169 | goto err; | ||
170 | |||
171 | ret = dht11_decode(dht11, | ||
172 | dht11->num_edges == DHT11_EDGES_PER_READ ? | ||
173 | DHT11_EDGES_PREAMBLE : | ||
174 | DHT11_EDGES_PREAMBLE - 2); | ||
175 | if (ret) | ||
176 | goto err; | ||
177 | } | ||
178 | |||
179 | ret = IIO_VAL_INT; | ||
180 | if (chan->type == IIO_TEMP) | ||
181 | *val = dht11->temperature; | ||
182 | else if (chan->type == IIO_HUMIDITYRELATIVE) | ||
183 | *val = dht11->humidity; | ||
184 | else | ||
185 | ret = -EINVAL; | ||
186 | err: | ||
187 | dht11->num_edges = -1; | ||
188 | return ret; | ||
189 | } | ||
190 | |||
191 | static const struct iio_info dht11_iio_info = { | ||
192 | .driver_module = THIS_MODULE, | ||
193 | .read_raw = dht11_read_raw, | ||
194 | }; | ||
195 | |||
196 | /* | ||
197 | * IRQ handler called on GPIO edges | ||
198 | */ | ||
199 | static irqreturn_t dht11_handle_irq(int irq, void *data) | ||
200 | { | ||
201 | struct iio_dev *iio = data; | ||
202 | struct dht11 *dht11 = iio_priv(iio); | ||
203 | |||
204 | /* TODO: Consider making the handler safe for IRQ sharing */ | ||
205 | if (dht11->num_edges < DHT11_EDGES_PER_READ && dht11->num_edges >= 0) { | ||
206 | dht11->edges[dht11->num_edges].ts = iio_get_time_ns(); | ||
207 | dht11->edges[dht11->num_edges++].value = | ||
208 | gpio_get_value(dht11->gpio); | ||
209 | |||
210 | if (dht11->num_edges >= DHT11_EDGES_PER_READ) | ||
211 | complete(&dht11->completion); | ||
212 | } | ||
213 | |||
214 | return IRQ_HANDLED; | ||
215 | } | ||
216 | |||
217 | static const struct iio_chan_spec dht11_chan_spec[] = { | ||
218 | { .type = IIO_TEMP, | ||
219 | .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), }, | ||
220 | { .type = IIO_HUMIDITYRELATIVE, | ||
221 | .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), } | ||
222 | }; | ||
223 | |||
224 | static const struct of_device_id dht11_dt_ids[] = { | ||
225 | { .compatible = "dht11", }, | ||
226 | { } | ||
227 | }; | ||
228 | MODULE_DEVICE_TABLE(of, dht11_dt_ids); | ||
229 | |||
230 | static int dht11_probe(struct platform_device *pdev) | ||
231 | { | ||
232 | struct device *dev = &pdev->dev; | ||
233 | struct device_node *node = dev->of_node; | ||
234 | struct dht11 *dht11; | ||
235 | struct iio_dev *iio; | ||
236 | int ret; | ||
237 | |||
238 | iio = devm_iio_device_alloc(dev, sizeof(*dht11)); | ||
239 | if (!iio) { | ||
240 | dev_err(dev, "Failed to allocate IIO device\n"); | ||
241 | return -ENOMEM; | ||
242 | } | ||
243 | |||
244 | dht11 = iio_priv(iio); | ||
245 | dht11->dev = dev; | ||
246 | |||
247 | dht11->gpio = ret = of_get_gpio(node, 0); | ||
248 | if (ret < 0) | ||
249 | return ret; | ||
250 | ret = devm_gpio_request_one(dev, dht11->gpio, GPIOF_IN, pdev->name); | ||
251 | if (ret) | ||
252 | return ret; | ||
253 | |||
254 | dht11->irq = gpio_to_irq(dht11->gpio); | ||
255 | if (dht11->irq < 0) { | ||
256 | dev_err(dev, "GPIO %d has no interrupt\n", dht11->gpio); | ||
257 | return -EINVAL; | ||
258 | } | ||
259 | ret = devm_request_irq(dev, dht11->irq, dht11_handle_irq, | ||
260 | IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING, | ||
261 | pdev->name, iio); | ||
262 | if (ret) | ||
263 | return ret; | ||
264 | |||
265 | dht11->timestamp = iio_get_time_ns() - DHT11_DATA_VALID_TIME - 1; | ||
266 | dht11->num_edges = -1; | ||
267 | |||
268 | platform_set_drvdata(pdev, iio); | ||
269 | |||
270 | init_completion(&dht11->completion); | ||
271 | iio->name = pdev->name; | ||
272 | iio->dev.parent = &pdev->dev; | ||
273 | iio->info = &dht11_iio_info; | ||
274 | iio->modes = INDIO_DIRECT_MODE; | ||
275 | iio->channels = dht11_chan_spec; | ||
276 | iio->num_channels = ARRAY_SIZE(dht11_chan_spec); | ||
277 | |||
278 | return devm_iio_device_register(dev, iio); | ||
279 | } | ||
280 | |||
281 | static struct platform_driver dht11_driver = { | ||
282 | .driver = { | ||
283 | .name = DRIVER_NAME, | ||
284 | .owner = THIS_MODULE, | ||
285 | .of_match_table = dht11_dt_ids, | ||
286 | }, | ||
287 | .probe = dht11_probe, | ||
288 | }; | ||
289 | |||
290 | module_platform_driver(dht11_driver); | ||
291 | |||
292 | MODULE_AUTHOR("Harald Geyer <harald@ccbib.org>"); | ||
293 | MODULE_DESCRIPTION("DHT11 humidity/temperature sensor driver"); | ||
294 | MODULE_LICENSE("GPL v2"); | ||