WiPy and DHT22 issue
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Hi all, Newbie here when it come to micropython so apologies in advance if there is something simple im missing.
Im attempting to connect a DHT22 to my WiPy on and expansion board 3.0 and have been unsuccessful with getting it to work
I have attempted to use the WiPy-2.0-DHT22 library from Erikdelange but when running the using_the_dht22.py file i keep getting the following errors
0 pulses measured
0 bits
[]
Traceback (most recent call last):
File "<stdin>", line 59, in <module>
IndexError: list index out of rangeI presume the list index out of range error is thrown as there are no pulses being measured so an empty list. However i have no idea why im getting no pulses measured and what i'm doing incorrectly unless i have screwed up the wiring or there is something else i need to change in the code.
Picture of wiring setup.
Any help would be appreciated.
Cheers
BN
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@brewnut Try this code. It works well for me. It should be in micrpython-lib, but I did not find it. Do not ask me why the class is DTH instead of DHT
import time import pycom from machine import Pin class DTHResult: 'DHT sensor result returned by DHT.read() method' ERR_NO_ERROR = 0 ERR_MISSING_DATA = 1 ERR_CRC = 2 error_code = ERR_NO_ERROR temperature = -1 humidity = -1 def __init__(self, error_code, temperature, humidity): self.error_code = error_code self.temperature = temperature self.humidity = humidity def is_valid(self): return self.error_code == DTHResult.ERR_NO_ERROR class DTH: 'DHT sensor (dht11, dht21,dht22) reader class for Pycom' __dhttype = 0 def __init__(self, pin, sensor=0): self.__pin = Pin(pin, mode=Pin.OPEN_DRAIN) self.__dhttype = sensor self.__pin(1) time.sleep(1.0) def read(self): # pull down to low self.__send_and_sleep(0, 0.019) data = pycom.pulses_get(self.__pin,100) self.__pin.init(Pin.OPEN_DRAIN) self.__pin(1) bits = [] for a,b in data: if a ==1 and 18 <= b <= 28: bits.append(0) if a ==1 and 65 <= b <= 75: bits.append(1) if len(bits) != 40: return DTHResult(DTHResult.ERR_MISSING_DATA, 0, 0) # we have the bits, calculate bytes the_bytes = self.__bits_to_bytes(bits) # calculate checksum and check checksum = self.__calculate_checksum(the_bytes) if the_bytes[4] != checksum: return DTHResult(DTHResult.ERR_CRC, 0, 0) # ok, we have valid data, return it [int_rh, dec_rh, int_t, dec_t, csum] = the_bytes if self.__dhttype==0: #dht11 rh = int_rh #dht11 20% ~ 90% t = int_t #dht11 0..50°C else: #dht21,dht22 rh = ((int_rh * 256) + dec_rh)/10 t = (((int_t & 0x7F) * 256) + dec_t)/10 if (int_t & 0x80) != 0: t = -t return DTHResult(DTHResult.ERR_NO_ERROR, t, rh) def __send_and_sleep(self, output, mysleep): self.__pin(output) time.sleep(mysleep) def __bits_to_bytes(self, bits): the_bytes = [] byte = 0 for i in range(0, len(bits)): byte <<= 1 if (bits[i]): byte |= 1 if ((i % 8) == 7): the_bytes.append(byte) byte = 0 return the_bytes def __calculate_checksum(self, the_bytes): return the_bytes[0] + the_bytes[1] + the_bytes[2] + the_bytes[3] & 255 th = DTH(Pin('P8', mode=Pin.OPEN_DRAIN),1) def run(): pycom.heartbeat(False) pycom.rgbled(0x000008) # blue time.sleep(0.5) result = th.read() if result.is_valid(): pycom.rgbled(0x001000) # green print("Temperature: %.1f C" % result.temperature) print("Humidity: %.1f %%" % result.humidity) run() -
@robert-hh thanks for this. I have also tried running this code from Jurassic Pork and i get nothing at all when i run it.
I have changed the pin to G22 so it matches my wiring for both sets of code.I will give the code from Daniel a go as well.
This is the code from Jurassic Pork
this is the DTH.py file
import time import pycom from machine import enable_irq, disable_irq, Pin class DTHResult: 'DHT sensor result returned by DHT.read() method' ERR_NO_ERROR = 0 ERR_MISSING_DATA = 1 ERR_CRC = 2 error_code = ERR_NO_ERROR temperature = -1 humidity = -1 def __init__(self, error_code, temperature, humidity): self.error_code = error_code self.temperature = temperature self.humidity = humidity def is_valid(self): return self.error_code == DTHResult.ERR_NO_ERROR class DTH: 'DHT sensor (dht11, dht21,dht22) reader class for Pycom' __pin = Pin(Pin.exp_board.G22, mode=Pin.OPEN_DRAIN) print(__pin) __dhttype = 1 def __init__(self, pin, sensor=1): self.__pin = Pin(pin, mode=Pin.OPEN_DRAIN) self.__dhttype = sensor self.__pin(1) time.sleep(1.0) def read(self): # pull down to low self.__send_and_sleep(0, 0.019) data = pycom.pulses_get(self.__pin,100) self.__pin.init(Pin.OPEN_DRAIN) self.__pin(1) #print(data) bits = [] for a,b in data: if a ==1 and 18 <= b <= 28: bits.append(0) if a ==1 and 65 <= b <= 75: bits.append(1) #print("longueur bits : %d " % len(bits)) if len(bits) != 40: return DTHResult(DTHResult.ERR_MISSING_DATA, 0, 0) #print(bits) # we have the bits, calculate bytes the_bytes = self.__bits_to_bytes(bits) # calculate checksum and check checksum = self.__calculate_checksum(the_bytes) if the_bytes[4] != checksum: return DTHResult(DTHResult.ERR_CRC, 0, 0) # ok, we have valid data, return it [int_rh, dec_rh, int_t, dec_t, csum] = the_bytes if self.__dhttype==0: #dht11 rh = int_rh #dht11 20% ~ 90% t = int_t #dht11 0..50°C else: #dht21,dht22 rh = ((int_rh * 256) + dec_rh)/10 t = (((int_t & 0x7F) * 256) + dec_t)/10 if (int_t & 0x80) > 0: t *= -1 return DTHResult(DTHResult.ERR_NO_ERROR, t, rh) def __send_and_sleep(self, output, mysleep): self.__pin(output) time.sleep(mysleep) def __bits_to_bytes(self, bits): the_bytes = [] byte = 0 for i in range(0, len(bits)): byte = byte << 1 if (bits[i]): byte = byte | 1 else: byte = byte | 0 if ((i + 1) % 8 == 0): the_bytes.append(byte) byte = 0 #print(the_bytes) return the_bytes def __calculate_checksum(self, the_bytes): return the_bytes[0] + the_bytes[1] + the_bytes[2] + the_bytes[3] & 255this is the DHT22_example.py code
import pycom import time from machine import Pin from dth import DTH pycom.heartbeat(False) pycom.rgbled(0x000008) # blue th = DTH(Pin.exp_board.G22,1) print(th) time.sleep(2) result = th.read() print(result) if result.is_valid(): pycom.rgbled(0x001000) # green print('Temperature: {:3.2f}'.format(result.temperature/1.0)) print('Humidity: {:3.2f}'.format(result.humidity/1.0))Running the DHT22_example code seems to stall somewhere after the LED changes to blue as it does not change to green. I presume this is because the result is not valid.
:-(
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Ok I have since added a one wire temp sensor to the board and got that working so have now come back to the dht22.
I am still getting the zero pulses received error so will look to see how I go debugging. Any tips would be appreciated.
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@brewnut When you take the voltage at the data pin, it should be about 3.3V. Do you have to visualize the data signal, like with a logic analyzer or Oscilloscope?
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@robert-hh no sorry I don’t have an Oscilloscope. Anything else I can do with the code to troubleshoot eg print out results at certain steps to see where it is failing?
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This post is deleted! -
@brewnut did you try to take my code example below and replace 'P8' by 'P12', which is your wiring?
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@robert-hh Hi Robert i have just tried your code replacing 'P8' with 'P11' (thats actually what the yellow jumper wire is plugged into).
Noting happens when running this.
I also tried replacing the __dhttype = 0 with = 1 as reading over the DTH code notes it mentions the DHT 11 sensor is type 0 and DHT 22 sensor is type 1.
Changing these settings also results in noting happening when running.
:-( -
If you want to use 'P11' (G22), try removing the 'RTS' jumper as it is connected to 'program port'.
See: https://docs.pycom.io/.gitbook/assets/wipy3-pinout.png -
@frida thanks for this suggestion, I will give a go and report back. Any particular reason the RTS jumper is linked to P11. Should I try a different pin instead and leave the RTS jumper in place?
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@brewnut The RTS pin is not used by the firmware, but driven by the UAB/UART bridge. But you can also use another pin, like P6.
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