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.

Install using make

Clone repo cd to repo directory run make run make install to place the necessary files in the kernel modules directory and /boot/overlays reboot

You can verify that it is working correctly by running this command, which should show similar output

# cat /sys/devices/platform/dht22\@0/iio\:device0/in_humidityrelative_input 
59.400000000