nmostw / NVidia-Jetson-DHT22-Python

A python library to read temperature and humidity from DHT22 sensor

DHT22 NVidia Jetson Python

A python library to read temperature from your DHT22 sensor connected on GPIO pins of your Jetson Development Kit

Based on https://github.com/jetsonhacks/jetsonTX1GPIO

• Copyright (c) 2015 JetsonHacks
• All rights reserved.

Prerequisites

Install python-dev

 sudo apt-get install python-dev

Setup

Edit C_DHT.c to edit the pin number you wish to use to communicate with your DHT22. Default set to:

#define PIN0 gpio 388  //2-pin from bottom left
#define PIN1 gpio 398  //6-th pin from bottom left

If you don't know the pin numbers google "Jetson gpio pinout tk1/tx1/tx2"

Install

Download project and install the python library:

cd /path/to/this/dir/
sudo python setup.py build
sudo python setup.py install

Now your python library is set up on your Jetson.

Usage

To read sensor enter python as superuser

sudo python
import C_DHT
C_DHT.readSensor(0)

Other

The library is written in C so it should run faster than python implementation would. DHT22 sends signals which need to be caught every 50 microseconds (not mili, micro).

The function C_DHT.readSensor(pinNumber) returns (temperature, humidity, 0 or 1) triplet as result. If the last value is 0 the communication failed so try again in 2 seconds. If 1 simply read the temperature and humidity.

The code sets the communication w/ the sensor on its own thread so it minimizes the chances of interrupt. Don't expect to get a reading every time you try to call the function. Give it a few times.

You can also modify it to read from DHT11 or DHT21 as well

Datasheet on: https://cdn-shop.adafruit.com/datasheets/Digital+humidity+and+temperature+sensor+AM2302.pdf