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DHT22 NVidia Jetson Python

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

DHT11 support

Also added a DHT11 sensor read - However this should be tested by someone.

List of supported Jetson boards

  • TX1
  • TX2
  • Xavier
  • Nano

Check the jetsonGPIO/jetsonGPIO.h for defines. It should be obvious which is which.

Prerequisites

Install python-dev

 sudo apt-get install python-dev

This repository relies on a fork I made. To clone the repository use:

 git clone --recurse-submodules -j8 https://github.com/GrgoMariani/NVidia-Jetson-DHT22-Python

Setup

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

#define PIN0 jetsontx2_pin37  //2-pin from bottom left
#define PIN1 jetsontx2_pin29  //6-th pin from bottom left

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

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

Once in python

import C_DHT
C_DHT.readSensor(0)        # if used with DHT22, read first sensor
C_DHT.readSensor(1)        # if used with DHT22, read second sensor
C_DHT.readSensorDHT11(0)   # if used with DHT11 sensors
C_DHT.readSensorDHT11(1)   # if used with DHT11 sensors

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. (Done recently)

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