python-gpsd-client

a gpsd-client in python is using python threading.

this is a test project only. use it at your own risk.

threads:

• thread WorkerDatabase is collecting data from a queue and store the data to a sqlite database.
• thread WorkerScript gets triggered to execute a script to do some stuff with the data in the sqlite database.
• thread WorkerGps is receiving gps data from a gpsd-server and put the data to a queue for thread WorkerDatabase.

in this example there are two WorkerGps threads to collect data from two different gpsd-servers (HOST_1 and HOST_2).

sqlite database content:

• table data_gps_tpv stores position data like: lat, lon, alt, ...
• table data_gps_sky stores satellite data: el, az, ...
• table data_gps_sky_map stores the strength of the satellites data accorting to their position on the sky (makes only sense when the gps device is at a fix position)

path:

the output path for the sqlite file is the temporary folder (e.g.: /tmp/), but can be changed in OUTPUT_PATH. the output path for the logging file is the temporary folder (e.g.: /tmp/), but can be changed in LOGGER_OUTPUT_PATH.

features:

• in case the gpsd-client isn't receiving data from the gpsd-server anymore for a certain number of seconds, a restart of the WorkerGps thread will be triggered.

  1. when gps-client receives no data at all for longer than TIMEOUT_STOP_WORKER_GPS.
  2. when gps-client returns no valid data for longer than TIMEOUT_STOP_WORKER_GPS.
  3. when gps-client returns same data over and over for longer than TIMEOUT_STOP_WORKER_GPS.

  it gives up and stops itself to get restarted. these three cases happens to me because i have a very weak wifi connection to my gpsd-server. and all the above cases i have to handle to get a reliable client.

• if the queue isn't filled up with data for a certain number of seconds (TIMEOUT_STOP_WORKER_DATABASE) the whole application will stop.

• the collected data will be stored to an in-memory sqlite database first and after a certain number of seconds (COMMIT_INTERVAL) the data will be stored to the database file, to reduce the disk I/O (wearout).

• at each commit to the database file, an optional script will be triggered by signaling the WorkerScript thread.
  in my case a gnuplot script (not included):
  

• logging debug information to a separate file

requirements:

• python 3.9 or newer
• APT package: gpsd-client 3.22 or newer. or compiled from newest source code
• APT package: sqlite3
• APT package: gnuplot (optional)

see also:

• my project RPi-GPS-PPS-StratumOne is setting up a gpsd-server you can use to collect gps data from.