/telegraf-input-dht_sensor

Primary LanguageGo

DHT Sensor plugin

Summary

This plugin collects temperature and humidity from DHTXX sensors (usually connected to Raspberry Pi or similar host).

Configuration

Sample config (see plugin.conf in the repo):

[[inputs.dht_sensor]]

    # type of the sensor you are using (check your invoice if not sure).
    # possible values: "DHT11", "DHT12", "DHT22"
    sensor = "DHT22"

    # which data pin are you connectinmg to? 
    # Check your wiring if you are not sure
    data_pin = 4

    # number of retries in case of a failure
    number_of_retries = 3
    
    # also retry if a sensor returns data outside the sanity range.
    # temperature is specified in degrees celsius.
    retry_humidity_above = 100
    retry_temperature_above = 80

Installation

  • Clone the repo
git clone
  • Build the "dht_sensor" binary
$ go build -o dht_sensor cmd/main.go

NOTE: if you are building for Raspbery PI, you need to either:

  1. Build it on the Raspberry Pi device itself, or
  2. Cross-compile.

Usually (2) should be quite simple, but go-dht library has a portion of the code implemented in C, so you will need to install a cross compiler for ARM, and cross-compile using the following:

# compile the module for amd64.
$ go build -o dht_sensor.amd64 cmd/main.go

# install the debian package for cross-compilation. 
# You may need a different arch (i.e. eabi instead of eabihf) depending on your target HW or OS.
# Debian Bookworm on RPi3 needs as eabihf, while Bullseye was fine with eabi.
$ sudo apt install gcc-10-arm-linux-gnueabihf

# compile for ARM64 (RPi4)
$ env GOOS=linux GOARCH=arm64 go build -o dht_sensor.arm64 cmd/main.go

# compile for ARMv7l (RPI3b)
$ env CC=arm-linux-gnueabihf-gcc-10 CGO_ENABLED=1  GOOS=linux GOARCH=arm GOARM=7 go build -o dht_sensor.armv7l cmd/main.go

# compile for ARMv6l (RPI Zero)
$ env CC=arm-linux-gnueabihf-gcc-10 CGO_ENABLED=1  GOOS=linux GOARCH=arm GOARM=6 go build -o dht_sensor.armv6l cmd/main.go

(notice the extra CC and CGO_ENABLED variables required for ARM6/7 in addition to regular Go cross-compile flags). It is probably easier to compile directly on RPi, but some peopel do not like to install DEV dependencies in production.

  • Edit the config
  • Copy the binary and the config to an appropriate location
$ sudo cp plugin.config /etc/telegraf/telegraf-dht_sensor.config
$ sudo cp dht_sensor /usr/lib/telegraf/plugins/
  • You should be able to call this from telegraf now using execd
[[inputs.execd]]
  command = ["/usr/lib/telegraf/plugins/dht_sensor", "-config", "/etc/telegraf/telegraf-dht_sensor.config" ]
  signal = "none"
  • If you get an error Error during call C.dial_DHTxx_and_read(): failed to open GPIO export for writing, this means that the user you are running telegraf under does not have permissions to open /sys/class/gpio/export. To fix this, simply add your telegraf user into gpio group, and restart telegraf:
$ systemctl status telegraf 
[...]
Aug 02 14:43:59 pi telegraf[2419]: 2021-08-02T21:43:59Z E! [inputs.execd] stderr: "failed to gather metrics: Error during call C.dial_DHTxx_and_read(): failed to open GPIO export for writing"
$ ls -l /sys/class/gpio/export
-rwxrwx--- 1 root gpio 4096 Jul 31 20:17 /sys/class/gpio/export
$ sudo usermod -a -G gpio telegraf
$ sudo systemctl restart telegraf

Credits

  • This self-contained plugin is based on the documentations of Execd Go Shim.
  • This plugin uses a fork of Go-DHT library. Most of the heavy lifting is done there. Huge kudos to the authors.