dht22 Kernel Driver

A DHT22 kernel driver for Raspberry Pi. See the specufication on http://www.electrodragon.com/w/AM2302

Add the "bin/dht22.dtbo" to the "/boot/overlays/" directory and add a lines with

# Enable DHT22 sensor
dtoverlay=dht22,gpiopin=4

to the /boot/config.txt

Do a "make" and a "modprobe industrialio; insmod dht22.ko" in the dmesg you should see now:

[  273.097098] chksum_ok = 1
[  273.097107] humidity = 42.0% RH
[  273.097116] temperature = 21.0° C

A cat "/proc/dht22/gpio04" shows:

root@pixel:~/Source/kernel/dht22# cat /proc/dht22/gpio04

DHT22 on gpio pin 4:
  temperature = 21.9° C
  humidity = 38.0% RH
  timestamp = 259
  no checksum error

To get the raw data you can read the values in the sys file system:

 /sys/bus/iio/devices/iio\:device0/in_temp_input
 /sys/bus/iio/devices/iio\:device0/in_humidityrelative_input

It shows the sensor values as integers.

You can copy the dht22.ko to the /lib/modules/uname -r/kernel/drivers/iio/humidity/ than the system should load the modul automaticaly. Do not forget to make a "depmod -a".

At the moment the driver is in a early beta stage. But you should not get read errors.