Gpsd data over MQTT

This purpose of this code is to send GPSD data from one Raspberry PI (RPI) and send it to Home Assistant on another RPI via MQTT.

Hardware Setup

1. 2 Raspberry pi's, one with Home Assistant running on it, second one has the GPS receiver attached
2. GPS receiver
3. On the RPI with the gps receiver attached, install gpsd and gpsdclient

Functionailty

This code will listen for events from a GPSD client (in my case a USB GPS receiver plugged into a RPI 3b+) It will then send the latitude and longitude coordinates along with some other gps data to Home Assistant via MQTT which in my case is on a seperate RPI 4.

This code triggers from a Cron task and records a successful outcome or a failure in a file called /home/pi/crontasks.log Use the command "cat /home/pi/crontasks.log" to view the contents of the log file once up and running or use "journalctl" command to view errors. The log file has a configurable size limit to it (default 50mb). Once the limit is reached the log is deleted and a new file is created.

Software setup

• Download the gpsdata.py file from this repository
• Place it on the RPI that has the GPS reciever attached. Recommend in /home/pi directory for simplicity
• Install gpsd and gpsdclient on the RPI

sudo apt-get update

sudo apt install gpsd

sudo apt install gpsdclient

• Open the gpsdata.py file

nano /home/pi/gpsdata.py

• Line 18 says "configure these". So in the block of code below that,
  • add your MQTT broker address,
  • username/password if required
  • and change the port if required.

NOTE: If you don't use mqtt username and passsword then comment both those lines with a # in the front of each of them.

• Change (or leave "caravan_gps_receiver") as the value for "deviceName" to suit your needs. but remember what you used for later HA configuration.

TIP - Throughout the code, Lines starting with # are comments to assist working out what the relevant code does.

TIP #2: Print messages in this code won't display during a cron task. To see print messages run this file manually from the command line. EG: python3 gpsdata.py

Home Assistant set up in the configuration.yaml

• Add the below to your configuration.yaml (home assistant versions 2022.6.9 ? and upwards )

mqtt:
  device_tracker:
    - name: "Caravan GPS receiver"
      state_topic: "homeassistant/caravan_gps_receiver/state"
      json_attributes_topic: "homeassistant/caravan_gps_receiver/attributes"
      json_attributes_template: "{{ value_json | tojson}}"

NOTE - Obviously change caravan_gps_receiver to the same topic name you choose when adding a name for "deviceName" in the code" and also change the "name:" value to what ever you want to call the device tracker.

• restart HA after editing the file

Home Assistant Automation

Now create a automation that triggers from a MQTT topic of "homeassistant/your_device_name/attributes". Once triggered use the set.location service as the action, as per below example.

- id: 1a06fb2f81d949c8ad6c1ff95b4d4d7c
 alias: Update Home Location
 trigger:
 - platform: mqtt
   topic: homeassistant/caravan_gps_receiver/attributes
 condition: []
 action:
 - service: homeassistant.set_location
   data_template:
     latitude: '{{ states.device_tracker.caravan_gps_receiver.attributes.latitude }}'
     longitude: '{{ states.device_tracker.caravan_gps_receiver.attributes.longitude
       }}'

Create the Cron task

In the terminal of the RPI with the receiver attached. type crontab -e and push enter. at the end of the file that opens add...

*/1 * * * * /usr/bin/python3 /home/pi/gpsdata.py

then save the file and the cron task will run. (in this case every minute). However, you can change it to every 15 minutes or what ever suits you.

for example

by changing */1 in the above line to */15 or read the crontab file to see what to change for various days months, hours etc

Hope that helps Enjoy

Final tips

• View the cron logs by typing /home/pi/crontasks.log in the terminal. The logs are nothing special, however they do let you know if its running as scheduled.
• View error logs by typing journalctl in the terminal
• Run the gps code manually with python3 /home/pi/gpsdata.py this is actually handy sometimes to also check for errors. and/or see the gpsd payload and log file size via print statements
• Line 38 lets you change log file size limits (in MB)
• Line 34 - logPayload = False
  • Set this value to True to have the raw data from gpsd stored in the log file for later reference