Python lesson 28-DHT11 doesn't work reliably

[Martin-HiPi]

This code needs to be reviewed for bad behaviour: https://github.com/Martin-HiPi/HiPi-Sensor-kit-v4.0/blob/f8d8c8ecc70f6f9e8cb72e3602bd26bba3683e8c/Python/28_humiture.py

[Martin-HiPi]

I think I found the root cause: the pin is not pulled low long enough!
The datasheet asks for at least 18ms and I'm measuring ~8us!

Edit: It's weirder than this, now the timing is good, but the DHT11 is not even responding...

[Martin-HiPi]

I find that the issue is those two lines:

HiPi-Sensor-kit-v4.0/Python/28_humiture.py

Lines 29 to 30 in f8d8c8e

	GPIO.setup(DHTPIN, GPIO.OUT)
	GPIO.output(DHTPIN, GPIO.HIGH)

Reason:
When the pin is set up as an output, it goes low for ~7us before the next code line brings it UP.

Solution:
Set up the GPIO as output and specify the initial level at the same time:
GPIO.setup(DHTPIN, GPIO.OUT, initial=GPIO.HIGH)

Replacing the two lines with the above code fixes initialization issues, and the lesson code works reliably!

[Martin-HiPi]

Fixed in commit https://github.com/Martin-HiPi/HiPi-Sensor-kit-v4.0/blob/cad43bf2dee7c40b0e8bf08987dc044e28a46675/Python/28_humiture.py