nebulx29/dht22

Description

dht22 is small utility that reads a DHT22 sensor (DHT11 should work as well, but is untested) and outputs its value to the commandline.

Download

Simply clone this repository to any directory you like

$ git clone https://github.com/nebulx29/dht22/

if you don't have GIT available, install it via

$ sudo apt-get install git-core

Prerequisites

In order to compile the utility you need GCC, Make and the wiringPi libraries. If you haven't already done so, you can install it via

$ sudo apt-get update
$ sudo apt-get upgrade
$ sudo apt-get install build-essential wiringpi

Remark: As i haven't testet it from a fresh build yet, please let me know in case i forgot something

The Makefile installs the binary per default to /home/pi/bin/dht22. If your prefer otherwise change the path in the file dht22\Makefile.

If you don't have a home/pi/bin/ directory yet, create it with the command mkdir /home/pi/bin.

Compile and install

$ mkdir /home/pi/bin
$ cd dht22
$ make install

Connecting the Sensor and GPIO numbering

Connect the DHT22 sensor to VCC, GND and DATA to a free GPIO PIN. The dht22 utiltity uses the wiringPi GPIO numbering scheme. In the subsequent examples GPIO 22 (wiringPi) ist used. On Raspberry Pi 3 this GPIO 22 (wiringPi) equals physical Pin #31 as well as GPIO 6 in BCM numbering.

$ gpio readall
 +-----+-----+---------+------+---+---Pi 3---+---+------+---------+-----+-----+
 | BCM | wPi |   Name  | Mode | V | Physical | V | Mode | Name    | wPi | BCM |
 +-----+-----+---------+------+---+----++----+---+------+---------+-----+-----+
...
 |   6 |  22 | GPIO.22 |   IN | 1 | 31 || 32 | 0 | IN   | GPIO.26 | 26  | 12  |
...
 +-----+-----+---------+------+---+----++----+---+------+---------+-----+-----+
 | BCM | wPi |   Name  | Mode | V | Physical | V | Mode | Name    | wPi | BCM |
 +-----+-----+---------+------+---+---Pi 3---+---+------+---------+-----+-----+

Usage

Usage: dht22 c|f|h pin
  where c reads temperature in degree celsius
        f reads temperature in degree fahrenheit
        h reads humidity
        pin is the GPIO pin used for the DHT11 data pin in wiringPi numbering

Here is an example test run:

$ cd /home/pi/bin
$ sudo ./dht22 c 22
25.1
$ sudo ./dht22 f 22
77.2
$ sudo ./dht22 h 22
43.0

nebulx29 / dht22