nmealogger - log NMEA data for offline analysis

Reads NMEA sentences from the network, adds timestamps and logs to files. The intended use is to capture instrument data from a sailing session and store it for later analysis. Assumes an NMEA network server running on port 10110 on localhost. Kplex works well, alternatively SignalK NMEA 0183 over IP should also work.

Example log data:

2024-07-15T13:09:48.683+0000    $IIRMC,130900,A,5930.975,N,02446.310,E,05.9,161,150724,00,E,A*0A
2024-07-15T13:09:48.746+0000    $IIVHW,,,117,M,05.7,N,,*61
2024-07-15T13:09:49.129+0000    $GPRMC,130949,A,5930.970,N,02446.315,E,05.7,160,150724,00,E,A*1F
2024-07-15T13:09:49.157+0000    $GPGLL,5930.970,N,02446.315,E,130949,A,A*43
2024-07-15T13:09:49.217+0000    $IIVLW,09452,N,030.8,N*52
2024-07-15T13:09:49.267+0000    $IIVWR,154,R,05.5,N,,,,*61

The log files will be created in /data after every 5 minutes. If an Internet connection is available the loguploader daemon will attempt to upload the finalized log files to Google Drive. Uploaded log files are renamed to have an .uploaded suffix and deleted from /data after a while.

Binaries built from the cmd directory:

• nmealogger - the logging daemon
• logupload - upload log files to Google drive from Pi
• logdownload - fetch log files in bulk from Google Drive and optionally clean up the Drive.
• nmeareplay - replay the log files from a network server. Enables offline use of tools such as NMEAremote.

Installation

make build builds a Debian package for arm32. This has been confirmed to work on both the earlier generation and later 64 bit Raspberry Pi-s. For other architectures the Dockerfile needs to be adjusted.

Copy the resulting .deb file to the Pi and install with dpkg -i. This will create the systemd services for NMEA logger, log uploader and cleanup. The services will be started automaticaly at system startup.

The /data directory needs to be created manually.

Uploading to Google Drive

Using Drive as log destination is convenient as ~everyone has it, it doesn't necessarily cost anything and has a decent API (if somewhat poorly documented). The setup can be a bit involved though: a cloud project needs to be created and an IAM service account. Use the Google Developer console. Download the service account credentials - these need to be configured for loguploader and logdownloader.

Create the destination folder in the Drive and note the folder ID from URL (this will need to be configured for the loguploader). Share the folder with the service account.