1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
|
/*
* Copyright (c) 2016 Intel Corporation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <device.h>
#include <gpio.h>
#include <misc/byteorder.h>
#include <misc/util.h>
#include <sensor.h>
#include <string.h>
#include <zephyr.h>
#include "dht.h"
/**
* @brief Measure duration of signal send by sensor
*
* @param drv_data Pointer to the driver data structure
* @param singnal_val Value of signal being measured
*
* @return duration in usec of signal being measured,
* -1 if duration exceeds DHT_SIGNAL_MAX_WAIT_DURATION
*/
static int8_t dht_measure_signal_duration(struct dht_data *drv_data,
uint32_t signal_val)
{
uint32_t val;
uint32_t elapsed_cycles;
uint32_t max_wait_cycles = (uint32_t)(
(uint64_t)DHT_SIGNAL_MAX_WAIT_DURATION *
(uint64_t)sys_clock_hw_cycles_per_sec /
(uint64_t)USEC_PER_SEC
);
uint32_t start_cycles = sys_cycle_get_32();
do {
gpio_pin_read(drv_data->gpio, CONFIG_DHT_GPIO_PIN_NUM, &val);
elapsed_cycles = sys_cycle_get_32() - start_cycles;
if (elapsed_cycles >= max_wait_cycles) {
return -1;
}
} while (val == signal_val);
return (uint64_t)elapsed_cycles *
(uint64_t)USEC_PER_SEC /
(uint64_t)sys_clock_hw_cycles_per_sec;
}
static int dht_sample_fetch(struct device *dev, enum sensor_channel chan)
{
struct dht_data *drv_data = dev->driver_data;
int ret = 0;
int8_t signal_duration[DHT_DATA_BITS_NUM];
int8_t max_duration, min_duration, avg_duration;
uint8_t buf[5];
unsigned int i, j;
__ASSERT_NO_MSG(chan == SENSOR_CHAN_ALL);
/* send start signal */
gpio_pin_write(drv_data->gpio, CONFIG_DHT_GPIO_PIN_NUM, 0);
k_busy_wait(DHT_START_SIGNAL_DURATION);
gpio_pin_write(drv_data->gpio, CONFIG_DHT_GPIO_PIN_NUM, 1);
/* switch to DIR_IN to read sensor signals */
gpio_pin_configure(drv_data->gpio, CONFIG_DHT_GPIO_PIN_NUM,
GPIO_DIR_IN);
/* wait for sensor response */
if (dht_measure_signal_duration(drv_data, 1) == -1) {
ret = -EIO;
goto cleanup;
}
/* read sensor response */
if (dht_measure_signal_duration(drv_data, 0) == -1) {
ret = -EIO;
goto cleanup;
}
/* wait for sensor data */
if (dht_measure_signal_duration(drv_data, 1) == -1) {
ret = -EIO;
goto cleanup;
}
/* read sensor data */
for (i = 0; i < DHT_DATA_BITS_NUM; i++) {
/* LOW signal to indicate a new bit */
if (dht_measure_signal_duration(drv_data, 0) == -1) {
ret = -EIO;
goto cleanup;
}
/* HIGH signal duration indicates bit value */
signal_duration[i] = dht_measure_signal_duration(drv_data, 1);
if (signal_duration[i] == -1) {
ret = -EIO;
goto cleanup;
}
}
/*
* the datasheet says 20-40us HIGH signal duration for a 0 bit and
* 80us for a 1 bit; however, since dht_measure_signal_duration is
* not very precise, compute the threshold for deciding between a
* 0 bit and a 1 bit as the average between the minimum and maximum
* if the durations stored in signal_duration
*/
min_duration = signal_duration[0];
max_duration = signal_duration[0];
for (i = 1; i < DHT_DATA_BITS_NUM; i++) {
if (min_duration > signal_duration[i]) {
min_duration = signal_duration[i];
}
if (max_duration < signal_duration[i]) {
max_duration = signal_duration[i];
}
}
avg_duration = ((int16_t)min_duration + (int16_t)max_duration) / 2;
/* store bits in buf */
j = 0;
memset(buf, 0, sizeof(buf));
for (i = 0; i < DHT_DATA_BITS_NUM; i++) {
if (signal_duration[i] >= avg_duration) {
buf[j] = (buf[j] << 1) | 1;
} else {
buf[j] = buf[j] << 1;
}
if (i % 8 == 7) {
j++;
}
}
/* verify checksum */
if (((buf[0] + buf[1] + buf[2] + buf[3]) & 0xFF) != buf[4]) {
SYS_LOG_DBG("Invalid checksum in fetched sample");
ret = -EIO;
} else {
memcpy(drv_data->sample, buf, 4);
}
cleanup:
/* switch to DIR_OUT and leave pin to HIGH until next fetch */
gpio_pin_configure(drv_data->gpio, CONFIG_DHT_GPIO_PIN_NUM,
GPIO_DIR_OUT);
gpio_pin_write(drv_data->gpio, CONFIG_DHT_GPIO_PIN_NUM, 1);
return ret;
}
static int dht_channel_get(struct device *dev,
enum sensor_channel chan,
struct sensor_value *val)
{
struct dht_data *drv_data = dev->driver_data;
__ASSERT_NO_MSG(chan == SENSOR_CHAN_TEMP || chan == SENSOR_CHAN_HUMIDITY);
val->type = SENSOR_VALUE_TYPE_INT_PLUS_MICRO;
/* see data calculation example from datasheet */
#if defined(CONFIG_DHT_CHIP_DHT11)
/* use only integral data byte */
if (chan == SENSOR_CHAN_HUMIDITY) {
val->val1 = drv_data->sample[0] * 1000;
val->val2 = 0;
} else { /* chan == SENSOR_CHAN_TEMP */
val->val1 = drv_data->sample[2];
val->val2 = 0;
}
#elif defined(CONFIG_DHT_CHIP_DHT22)
/*
* use both integral and decimal data bytes; resulted 16bit data has
* a resolution of 0.1 units
*/
int16_t raw_val, sign;
if (chan == SENSOR_CHAN_HUMIDITY) {
raw_val = (drv_data->sample[0] << 8) | drv_data->sample[1];
val->val1 = raw_val * 100;
val->val2 = 0;
} else { /* chan == SENSOR_CHAN_TEMP */
raw_val = (drv_data->sample[2] << 8) | drv_data->sample[3];
sign = raw_val & 0x8000;
raw_val = raw_val & ~0x8000;
val->val1 = raw_val / 10;
val->val2 = (raw_val % 10) * 100000;
/* handle negative value */
if (sign) {
val->val1 = -val->val1;
val->val2 = -val->val2;
}
}
#endif
return 0;
}
static const struct sensor_driver_api dht_api = {
.sample_fetch = &dht_sample_fetch,
.channel_get = &dht_channel_get,
};
static int dht_init(struct device *dev)
{
struct dht_data *drv_data = dev->driver_data;
drv_data->gpio = device_get_binding(CONFIG_DHT_GPIO_DEV_NAME);
if (drv_data->gpio == NULL) {
SYS_LOG_ERR("Failed to get GPIO device.");
return -EINVAL;
}
gpio_pin_configure(drv_data->gpio, CONFIG_DHT_GPIO_PIN_NUM,
GPIO_DIR_OUT);
gpio_pin_write(drv_data->gpio, CONFIG_DHT_GPIO_PIN_NUM, 1);
dev->driver_api = &dht_api;
return 0;
}
struct dht_data dht_data;
DEVICE_INIT(dht_dev, CONFIG_DHT_NAME, &dht_init, &dht_data,
NULL, POST_KERNEL, CONFIG_SENSOR_INIT_PRIORITY);
|
