DHT-Blinka fail when using libgpiod

[yeyeto2788]

I just wanted to test the DHT22 sensor as in https://learn.adafruit.com/dht-humidity-sensing-on-raspberry-pi-with-gdocs-logging/python-setup but first test the functionality of Blinka.

Also I just encountered this using digitalio.DigitalInOut:

In [9]: dhtDevice = adafruit_dht.DHT22(pin)

In [10]: dhtDevice.temperature
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-10-bb6e5b54f869> in <module>()
----> 1 dhtDevice.temperature

/usr/local/lib/python3.7/dist-packages/adafruit_dht.py in temperature(self)
    225             data returned from the device (try again)
    226         """
--> 227         self.measure()
    228         return self._temperature
    229 

/usr/local/lib/python3.7/dist-packages/adafruit_dht.py in measure(self)
    179                 pulses = self._get_pulses_pulseio()
    180             else:
--> 181                 pulses = self._get_pulses_bitbang()
    182             #print(len(pulses), "pulses:", [x for x in pulses])
    183 

/usr/local/lib/python3.7/dist-packages/adafruit_dht.py in _get_pulses_bitbang(self)
    135         """
    136         pulses = array.array('H')
--> 137         with DigitalInOut(self._pin) as dhtpin:
    138             # we will bitbang if no pulsein capability
    139             transitions = []

/usr/local/lib/python3.7/dist-packages/digitalio.py in __init__(self, pin)
     82 
     83     def __init__(self, pin):
---> 84         self._pin = Pin(pin.id)
     85         self.direction = Direction.INPUT
     86 

AttributeError: 'DigitalInOut' object has no attribute 'id'

and using the board.PXX I get this:

In [1]: import board

In [2]: import adafruit_dht

In [3]: dhtDevice = adafruit_dht.DHT22(board.PC4)

In [4]: dhtDevice.temperature
---------------------------------------------------------------------------
NotImplementedError                       Traceback (most recent call last)
<ipython-input-4-bb6e5b54f869> in <module>()
----> 1 dhtDevice.temperature

/usr/local/lib/python3.7/dist-packages/adafruit_dht.py in temperature(self)
    225             data returned from the device (try again)
    226         """
--> 227         self.measure()
    228         return self._temperature
    229 

/usr/local/lib/python3.7/dist-packages/adafruit_dht.py in measure(self)
    179                 pulses = self._get_pulses_pulseio()
    180             else:
--> 181                 pulses = self._get_pulses_bitbang()
    182             #print(len(pulses), "pulses:", [x for x in pulses])
    183 

/usr/local/lib/python3.7/dist-packages/adafruit_dht.py in _get_pulses_bitbang(self)
    147             dhtval = True   # start with dht pin true because its pulled up
    148             dhtpin.direction = Direction.INPUT
--> 149             dhtpin.pull = Pull.UP
    150             while time.monotonic() - timestamp < 0.25:
    151                 if dhtval != dhtpin.value:

/usr/local/lib/python3.7/dist-packages/digitalio.py in pull(self, pul)
    137             self.__pull = pul
    138             if pul is Pull.UP:
--> 139                 self._pin.init(mode=Pin.IN, pull=Pin.PULL_UP)
    140             elif pul is Pull.DOWN:
    141                 if hasattr(Pin, "PULL_DOWN"):

/usr/local/lib/python3.7/dist-packages/adafruit_blinka/microcontroller/generic_linux/libgpiod_pin.py in init(self, mode, pull)
     45                 if pull != None:
     46                     if pull == self.PULL_UP:
---> 47                         raise NotImplementedError("Internal pullups not supported in libgpiod, use physical resistor instead!")
     48                     elif pull == self.PULL_DOWN:
     49                         raise NotImplementedError("Internal pulldowns not supported in libgpiod, use physical resistor instead!")

NotImplementedError: Internal pullups not supported in libgpiod, use physical resistor instead!

Is it possible to set a different pull on pin? Let's say I have already connected the physical resistor on the sensor.

More details:

Python 3.7.3 (default, Apr  3 2019, 05:39:12) 
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import board
>>> board.detector.chip.id
'SUN8I'
>>> board.detector.board.id
'ORANGE_PI_PLUS_2E'
>>> 

This relates to: adafruit/Adafruit_Blinka#245

[evaherrada]

@yeyeto2788 I just wanted to confirm that you do in fact have a physical resistor connected, your wording was slightly vague.

[yeyeto2788]

Hey @dherrada I connected it to the pin directly but I don't know if the error comes from the library by requiring to have a pull up or pull down resistor connected, as it checks for it. You can see it on the log already attached to this issue.

Even if I had connected the pin to a resistor it will through the same error because I didn't see a way of passing the pull up or down parameter.

If there is anything else I can help woth just let me know.

[evaherrada]

@yeyeto2788 Yeah, the error is coming from the library, as in the library (libgpiod) is raising the error, but it's failing exactly like it's supposed to. It's not a parameter that you pass, it's a physical resistor you connect. I'm not sure if you purchased the DHT22 from Adafruit, but if you did, you should have received also received a 4.7k or 10k resistor, which is required to use the DHT11 or DHT22 because libgpiod does not support using internal pullups.

Make sure it's hooked up like it is in this picture here: https://cdn-learn.adafruit.com/assets/assets/000/001/861/original/raspberry_pi_dht22wiring.gif?1447864317

By the way, you're using a dht22 that has headers that you put into a breadboard, not an AM2302 which has 3 wires coming out of it, right?

[yeyeto2788]

I did connected to a sensor board like this one https://www.amazon.es/DSD-TECH-humedad-temperatura-Raspberry/dp/B07CM2VLBK/ref=mp_s_a_1_1_sspa?adgrpid=63969568209&dchild=1&gclid=EAIaIQobChMIgbnQl8rS6gIVWbvVCh30eQlwEAAYASAAEgJUsPD_BwE&hvadid=308125539048&hvdev=m&hvlocphy=9047050&hvnetw=g&hvqmt=e&hvrand=12206774846927860259&hvtargid=kwd-300180952450&hydadcr=26398_1795523&keywords=dht22+sensor&qid=1594930252&sr=8-1-spons&tag=hydesmo-21&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExWDZHQjNPVTVSSUZMJmVuY3J5cHRlZElkPUExMDQ0NzU5V01ZWThUM0VUVFRWJmVuY3J5cHRlZEFkSWQ9QTEwMzk0NjkyOVc3NzBESjZSTDZLJndpZGdldE5hbWU9c3BfcGhvbmVfc2VhcmNoX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU= ans as far as I know it has a resistor conected to the sensor.

So let's say that sensor board has the resistor on the board, how do tell libgpiod that you have connected a resistor to the sensor?

[evaherrada]

Ok, that's definitely not supposed to happen. I can't tell you off the top of my head, but I can take a look into this sometime within the next few days

[evaherrada]

Also, do you mind posting the code you're using? I'd assume it's probably the same as what's in the tutorial you linked, but it's a lot easier to replicate the issue if I can be sure I'm running exactly what you are

[yeyeto2788]

import board​
import adafruit_dht​
dhtDevice = adafruit_dht.DHT22(board.PC4)​
dhtDevice.temperature

That would be code.

Take into account that I used a Orange Pi but I guess the error wikk be the same on other boards.

[SecT0uch]

Hi all,

I'm having the exact same issue with an AM2302 (Supposed to have a built-in pull-up resistor) on my Pine A64 LTS.

@yeyeto2788, did you figure it out ?

[yeyeto2788]

Hey @SecT0uch! Nope, I didn't figure out the issue but I can test it again to see if it now works (assuming there have been changes on dependencies and or this repository).

[SecT0uch]

Hey @yeyeto2788 ! Yes, if you have time testing that, that'd be great.
It doesn't seem to work on a non-pi device.
Thanks,

[yeyeto2788]

Tried and same error:

Traceback (most recent call last):
  File "test.py", line 5, in <module>
    print(dhtDevice.temperature)
  File "/home/yeyeto2788/workspace/dht11_test/venv/lib/python3.8/site-packages/adafruit_dht.py", line 253, in temperature
    self.measure()
  File "/home/yeyeto2788/workspace/dht11_test/venv/lib/python3.8/site-packages/adafruit_dht.py", line 200, in measure
    pulses = self._get_pulses_bitbang()
  File "/home/yeyeto2788/workspace/dht11_test/venv/lib/python3.8/site-packages/adafruit_dht.py", line 163, in _get_pulses_bitbang
    dhtpin.pull = Pull.UP
  File "/home/yeyeto2788/workspace/dht11_test/venv/lib/python3.8/site-packages/digitalio.py", line 170, in pull
    self._pin.init(mode=Pin.IN, pull=Pin.PULL_UP)
  File "/home/yeyeto2788/workspace/dht11_test/venv/lib/python3.8/site-packages/adafruit_blinka/microcontroller/generic_linux/libgpiod_pin.py", line 54, in init
    raise NotImplementedError(
NotImplementedError: Internal pullups not supported in libgpiod, use physical resistor instead!

Python: Python 3.8.5

Libraries installed:

Adafruit-Blinka==5.8.0
adafruit-circuitpython-dht==3.5.1
Adafruit-PlatformDetect==2.22.2
Adafruit-PureIO==1.1.7

Test script:

import board
import adafruit_dht
dhtDevice = adafruit_dht.DHT11(board.PG7)
print(dhtDevice.temperature)

Board: Orange Pi Lite

[yeyeto2788]

Update:
Maybe I was too optimistic and secure on my side to do some local changes to the libgpiod.py file and got this error:

Internal pullups not supported in libgpiod, use physical resistor instead!
Invalid pull for pin: 199
Traceback (most recent call last):
  File "test.py", line 5, in <module>
    print(dhtDevice.temperature)
  File "/home/yeyeto2788/workspace/dht11_test/venv/lib/python3.8/site-packages/adafruit_dht.py", line 253, in temperature
    self.measure()
  File "/home/yeyeto2788/workspace/dht11_test/venv/lib/python3.8/site-packages/adafruit_dht.py", line 209, in measure
    raise RuntimeError("A full buffer was not returned. Try again.")
RuntimeError: A full buffer was not returned. Try again.

NOTE: Forget the 2 first lines since I just change the raise for a print to see what this will lead me to.

The interesting part though is that I got some pulses by uncommenting this:

Internal pullups not supported in libgpiod, use physical resistor instead!n3.8/site-packages/adafruit_dht.py
Invalid pull for pin: 199
24 pulses: [10897, 6215, 13771, 6207, 13796, 6184, 13811, 6201, 13776, 6202, 13817, 6183, 13826, 6183, 13807, 6200, 13788, 6198, 13820, 6175, 13814, 6206, 13763, 6209]
Traceback (most recent call last):
  File "test.py", line 5, in <module>
    print(dhtDevice.temperature)
  File "/home/yeyeto2788/workspace/dht11_test/venv/lib/python3.8/site-packages/adafruit_dht.py", line 253, in temperature
    self.measure()
  File "/home/yeyeto2788/workspace/dht11_test/venv/lib/python3.8/site-packages/adafruit_dht.py", line 209, in measure
    raise RuntimeError("A full buffer was not returned. Try again.")
RuntimeError: A full buffer was not returned. Try again.

So I decided to try at lest 10 time by modifying the test.py file to:

import time
import board
import adafruit_dht
dhtDevice = adafruit_dht.DHT11(board.PG7)

for try_number in range(1,11):
  print(f"Try number {try_number}")
  try:
    print(dhtDevice.temperature)
  except RuntimeError:
    time.sleep(2)

And got different pulse every time:

Try number 1
Internal pullups not supported in libgpiod, use physical resistor instead!
Invalid pull for pin: 199
24 pulses: [13987, 6131, 13866, 6106, 13882, 6120, 13892, 6103, 13872, 6110, 13875, 6117, 13865, 6112, 13902, 6093, 13914, 6077, 13891, 6103, 13864, 6136, 13896, 6084]
Try number 2
Internal pullups not supported in libgpiod, use physical resistor instead!
Invalid pull for pin: 199
25 pulses: [3409, 6760, 13294, 6569, 13457, 6504, 13489, 6496, 13487, 6493, 13498, 6515, 13495, 6494, 13502, 6490, 13472, 6530, 13501, 6474, 13489, 6519, 13468, 6520, 13512]
Try number 3
Internal pullups not supported in libgpiod, use physical resistor instead!
Invalid pull for pin: 199
24 pulses: [10641, 6552, 13439, 6544, 13470, 6510, 13481, 6490, 13501, 6497, 13462, 6538, 13500, 6485, 13514, 6472, 13506, 6475, 13484, 6528, 13449, 6544, 13460, 6522]
Try number 4
Internal pullups not supported in libgpiod, use physical resistor instead!
Invalid pull for pin: 199
24 pulses: [17770, 6501, 13478, 6518, 13486, 6504, 13437, 6552, 13469, 6531, 13480, 6499, 13505, 6485, 13494, 6497, 13461, 6533, 13461, 6520, 13512, 6497, 13521, 6461]
Try number 5
Internal pullups not supported in libgpiod, use physical resistor instead!
Invalid pull for pin: 199
25 pulses: [4826, 6570, 13385, 6508, 13436, 6557, 13449, 6527, 13483, 6515, 13484, 6489, 13534, 6484, 13471, 6504, 13474, 6520, 13481, 6503, 13482, 6531, 13462, 6522, 13497]
Try number 6
Internal pullups not supported in libgpiod, use physical resistor instead!
Invalid pull for pin: 199
24 pulses: [12096, 6522, 13435, 6546, 13431, 6552, 13479, 6502, 13491, 6499, 13482, 6501, 13459, 6533, 13466, 6529, 13501, 6489, 13516, 6465, 13521, 6476, 13498, 6490]
Try number 7
Internal pullups not supported in libgpiod, use physical resistor instead!
Invalid pull for pin: 199
24 pulses: [19275, 6572, 13415, 6554, 13269, 6852, 13337, 6537, 13430, 6548, 13457, 6539, 13428, 6536, 13492, 6494, 13509, 6518, 13457, 6517, 13447, 6541, 13437, 6568]
Try number 8
Internal pullups not supported in libgpiod, use physical resistor instead!
Invalid pull for pin: 199
25 pulses: [7159, 6622, 13386, 6569, 13447, 6526, 13454, 6535, 13478, 6520, 13438, 6532, 13471, 6519, 13473, 6527, 13454, 6540, 13443, 6546, 13474, 6528, 13478, 6495, 13506]
Try number 9
Internal pullups not supported in libgpiod, use physical resistor instead!
Invalid pull for pin: 199
24 pulses: [14201, 6427, 13555, 6435, 13570, 6403, 13582, 6405, 13600, 6400, 13614, 6374, 13615, 6384, 13634, 6351, 13656, 6340, 13631, 6355, 13643, 6353, 13651, 6322]
Try number 10
Internal pullups not supported in libgpiod, use physical resistor instead!
Invalid pull for pin: 199
26 pulses: [1721, 5858, 13692, 6497, 13466, 6506, 13510, 6490, 13490, 6493, 13497, 6507, 13527, 6444, 13522, 6485, 13521, 6470, 13513, 6481, 13521, 6448, 13545, 6473, 13532, 6459]