r-pi_DHT11

DHT11 sensor readings with python

This is a variation of some DHT11 util found on the web. The one I found did everything by the book:

1. fetch data from sensor
2. validate checksum

In step 1 util used sleep(xx) between polling each bit which resulted in lots of bits either missing or repeated and checksums almost never were correct.

In this variation I actively poll 1000 bits from the sensor w/o any timeouts. Of course lots of bits do repeat. I divide the array into blocks of ones (HIs) and calculate average length of those blocks. Each block longer than avg will represent HI and every one shorter than avg -- LO. Like that:

11111111111100000011111100000000001111111111111110000000111110000011111100000011111111111111111

    1               0                    1                0          0               1

becomes

101001

And then I do the rest.

PROS:

• 90% of polls return correct data

CONS:

• the faster CPU the more memory will be required for buffer (default -- 1000)