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
|
#!/usr/bin/env python
# -*- coding: utf-8 -*-
from __future__ import absolute_import, division, print_function, unicode_literals
import time
import pigpio
class DHT11(object):
"""
The DHT11 class is a stripped version of the DHT22 sensor code by joan2937.
You can find the initial implementation here:
- https://github.com/srounet/pigpio/tree/master/EXAMPLES/Python/DHT22_AM2302_SENSOR
example code:
>>> pi = pigpio.pi()
>>> sensor = DHT11(pi, 4) # 4 is the data GPIO pin connected to your sensor
>>> for response in sensor:
.... print("Temperature: {}".format(response['temperature']))
.... print("Humidity: {}".format(response['humidity']))
"""
def __init__(self, pi, gpio):
"""
pi (pigpio): an instance of pigpio
gpio (int): gpio pin number
"""
self.pi = pi
self.gpio = gpio
self.high_tick = 0
self.bit = 40
self.temperature = 0
self.humidity = 0
self.either_edge_cb = None
self.setup()
def setup(self):
"""
Clears the internal gpio pull-up/down resistor.
Kills any watchdogs.
"""
self.pi.set_pull_up_down(self.gpio, pigpio.PUD_OFF)
self.pi.set_watchdog(self.gpio, 0)
self.register_callbacks()
def register_callbacks(self):
"""
Monitors RISING_EDGE changes using callback.
"""
self.either_edge_cb = self.pi.callback(
self.gpio,
pigpio.EITHER_EDGE,
self.either_edge_callback
)
def either_edge_callback(self, gpio, level, tick):
"""
Either Edge callbacks, called each time the gpio edge changes.
Accumulate the 40 data bits from the dht11 sensor.
"""
level_handlers = {
pigpio.FALLING_EDGE: self._edge_FALL,
pigpio.RISING_EDGE: self._edge_RISE,
pigpio.EITHER_EDGE: self._edge_EITHER
}
handler = level_handlers[level]
diff = pigpio.tickDiff(self.high_tick, tick)
handler(tick, diff)
def _edge_RISE(self, tick, diff):
"""
Handle Rise signal.
"""
val = 0
if diff >= 50:
val = 1
if diff >= 200: # Bad bit?
self.checksum = 256 # Force bad checksum
if self.bit >= 40: # Message complete
self.bit = 40
elif self.bit >= 32: # In checksum byte
self.checksum = (self.checksum << 1) + val
if self.bit == 39:
# 40th bit received
self.pi.set_watchdog(self.gpio, 0)
total = self.humidity + self.temperature
# is checksum ok ?
if not (total & 255) == self.checksum:
raise
elif 16 <= self.bit < 24: # in temperature byte
self.temperature = (self.temperature << 1) + val
elif 0 <= self.bit < 8: # in humidity byte
self.humidity = (self.humidity << 1) + val
else: # skip header bits
pass
self.bit += 1
def _edge_FALL(self, tick, diff):
"""
Handle Fall signal.
"""
self.high_tick = tick
if diff <= 250000:
return
self.bit = -2
self.checksum = 0
self.temperature = 0
self.humidity = 0
def _edge_EITHER(self, tick, diff):
"""
Handle Either signal.
"""
self.pi.set_watchdog(self.gpio, 0)
def read(self):
"""
Start reading over DHT11 sensor.
"""
self.pi.write(self.gpio, pigpio.LOW)
time.sleep(0.017) # 17 ms
self.pi.set_mode(self.gpio, pigpio.INPUT)
self.pi.set_watchdog(self.gpio, 200)
time.sleep(0.2)
def close(self):
"""
Stop reading sensor, remove callbacks.
"""
self.pi.set_watchdog(self.gpio, 0)
if self.either_edge_cb:
self.either_edge_cb.cancel()
self.either_edge_cb = None
def __iter__(self):
"""
Support the iterator protocol.
"""
return self
def next(self):
"""
Call the read method and return temperature and humidity informations.
"""
self.read()
response = {
'humidity': self.humidity,
'temperature': self.temperature
}
return response
if __name__ == '__main__':
pi = pigpio.pi()
sensor = DHT11(pi, 4)
for d in sensor:
print("temperature: {}".format(d['temperature']))
print("humidity: {}".format(d['humidity']))
time.sleep(1)
sensor.close()
|
