MMM-DHT22 Humidity and Temperature Module

Johans

@ Bangee
installed modules as described in read.me file but I get no reading of temp or hum.
sensor is working, tested with AdaFruit example

sudo ./AdafruitDHT.py 2302 27 (Data connected to gpio 27)
I get a perfect temp & hum reading, so i’m shure sensor is working.
i’m using an RPI3 - according to wiring pin, wpi 2 = gpio27 = physical pin 13.
I think wiring is OK.

only clock and this module installed.

PaulB

Hey guys :) Hope you are all good.
Finally I have the time to work on this module again :)
I had the same errors like you before and unsuprisingly did not found a solution for it.

Is someone in this thread still active?

Johans

@PaulB - glad you have found some time to work on it.
Yes I still have the problem with reading the data in the MM.
Hope you can find the cause. I would like to help you, but i’m not a programmer.
The only thing I could help on is perhaps some beta testing.
Cheers.
Johan

DocVooDoo

Hey, i have the same problem.
With “./Adafruit_Python_DHT/examples/AdafruitDHT.py 22 27” comes the Temperatur “Temp=20.1* Humidity=29.3%”
The DHT22 is Pinned on PIN 13 (27) (WiringPi 2). On the Mirror is the Temperatur and the Humidity undefined.
Whats the Problem? I found nothing…

ryck

@DocVooDoo Then I don’t know, maybe there is something wrong with the module…

Have you tried mine? https://github.com/ryck/MMM-DHT-Sensor

DocVooDoo

@ryck Hi. yes, a minute ago. He says “no data returned”.

ryck

@DocVooDoo sometimes the raspberry pi needs some time to pick up the values… try to increase the update time (ie, 30 seconds) and wait for it to update a couple of times…

DocVooDoo

@ryck nothing has changed. i have “node serveronly” running, and the log says “Error: failed to read sensor at Error (native)”
but the sensor works… look

ryck

@DocVooDoo Weird… did you follow all the instructions? ie, install bcm2835, npm install, etc?

DocVooDoo

@ryck Yes of course.

ryck

@DocVooDoo No idea then… Can you paste here the error you get?

DocVooDoo

@ryck only this Bild Text
then nothing on the log in node serveronly screen

ryck

@DocVooDoo well, no idea then… Have you tried to run the normal version (instead of the serveronly)?

DocVooDoo

@ryck yes, the same problem…

DocVooDoo

@ryck is it possible that the module root rights needs but does not get?

with another module comes the same error. root privileges are needed there

ryck

@DocVooDoo I guess that depends on how you installed magicmirror… did you use sudo?

DocVooDoo

@ryck no, without sudo. only with the command
bash -c “$(curl -sL https://raw.githubusercontent.com/MichMich/MagicMirror/master/installers/raspberry.sh)”

yawns

Some modules or dependencies require access to the GPIO
The DHT sensor module I wrote needs this as well.
In terminal please try this
sudo adduser -g $USER gpio

I can’t remember if you need to reboot afterwards, but it won’t hurt. Then try again accessing the sensor

DocVooDoo

@yawns
Hi. Thanks for your help. The user “pi” is already a member of the group “gpio”.

With Adafruit works the Sensor. Whether with or without sudo…

pinsdorf

Any updates on this? I have the same problems as @DocVooDoo and others, i.e. Adafruit code works like a charm, dht_var not.

Difference I noticed is that dht_var uses wiringpi library and Adafruit not?! I tried a reinstall of wiringpi package without success.

Next, I compared the implementations of dht_var and the Adafruit driver for DHT22.

The essence of the Adafruit code is in file Adafruit_Python_DHT/source/Raspberry_Pi_2/pi_2_dht_read.c. It is meant for Pi2 and Pi3, implemented in C, and defines a function int pi_2_dht_read(int type, int pin, float* humidity, float* temperature). It implements the communication with the sensor using a 1-wire bus. The rest of the Adafruit package is mostly (well-done) sugar-coating for Python usage and selecting the right driver for any given platform.

We could simply rewrite dht_var by using this driver code. What do you think?