This is a variation of the Microdexed Touch FM Synth (Yamaha-DX7) by Codeberg-positionhigh. It replaced the 2.8 inch LCD with a 3.2 inch LCD, and used full-sized Midi in and out sockets, with a 6N137 for the Midi input. Compiled version 1.53 PSRAM+Flash firmware was used.
It is constructed on stripboard and a Fritzing layout is included here, as are the case 3d-files.
Note the warning when using i2c Backpacks with 5v LCD displays and 3v3 MCU's or Raspberry Pi's