The folks over at Ham Radio Workbench (hamradioworkbench.com) have developed a generic development platform ("Benchduino") that has pluggable CPU daughterboards.

I have developed a daughterboard for the Teensy 4.1 (should also work on the 4.0 version too). The gerbers and the Eagle design files are currently stored in the "Files" section of the "SoftwareControlledHamRadio" groups.io :

https://groups.io/g/SoftwareControll...ghter%20Boards

They are also in the files section of the Ham Radio Workbench Facebook page.

Not 100% tested (i.e. use at your own risk, no warranty, etc. etc....). But let me know if you find any problems.

73
Mark
AJ6CU