There's not a whole lot to this project. Just a text parser for generic GPSs to connect to the Yaesu VX-8DR.
Using the Sededuino Xiao allows the whole project to be powered from the radio. In the minimalist implementation, only a Yaesu CT-M11 cable, a GPS module (eg Beitian BN-220 works well), a Seeedunino Xiao, and some minor soldering are required.
Additionally, the codebase will accept arbitrary field-lengths and decimal precision in the NMEA input. This means a very wide array of GPS modules (other than the recommended UBlox-chipset ones) will work without modifying the code.
Full documentation is available at the link below, including schematics, related projects, and far more than you ever wanted to know about the Yaesu GPS format.
Basic hardware and background information: https://blog.waterstar.run/2021/03/a-simplified-vx-8dr-gps-design.html
Extended hardware construction guide: https://blog.waterstar.run/2021/11/a-vx-8dr-gps-and-audio-interface-board.html
An extended version of the hardware (with a MOSFET to power/depower the GPS) has been released. It is designed to depower the GPS module during headset jack transmission to prevent noise from the module. In addition the GPS can be soft-switched off when the circuit is used purely as a headset adaptor. The hardware also has the ADC/DACs of the microcontroller connected to the speaker/microphone connections, leading to potential uses such as AFSK and other in-band signalling. The USB-C port on the microcontroller can even be used as a serial interface to a PC.
EasyEDA project for the enhanced version is available at the link below:
https://easyeda.com/WaterstarRunner/vx8-gps-audio-module
A unified software package will be desirable to produce in the near future. But due to some tri-stated pins on the basic hardware that are read by the extended hardware, there are currently two separate software packages for the two hardware versions.
Basic version: https://github.com/WaterstarRunner/VX8GPS-Xiao/archive/refs/tags/BasicHW-v1.0.zip
Extended version: https://github.com/WaterstarRunner/VX8GPS-Xiao/archive/refs/tags/ExtendedHW-v1.0e.zip