Click on the green "Code" button above and select "Download Zip" to download the entire support folder.
In this repository are many files containing the firmware and pcb layouts to make the hardware for AgOpenGPS.
The Arduino folder contains all the "older" firmware that worked with the Nano for steering, machine control, and the no longer used external IMU.
The Misc folder has various projects including Matthias switch syste, ESP32 projects etc.
The Teensy folder has the latest All in One firmware and PCB gerbers etc.