If you're an enthusiast of retrocomputing, NORFlasherFirmware will let you flash custom firmware for the NOR flash supported by the Z80-based homebrew computer kit.

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This project is an open source firmware flasher targeting an Arduino Mega 2560 / ATMega2560 MCU. The codebase in this repository is the code that will run on your new flashing unit. It currently supports the ST39SF0X0 (ST39SF040, ST39SF020, etc) NOR flash chip and accepts payloads over serial. XMODEM support is implemented.

A manufacturable PCB design is also included and can be sent to a variety of small-scale PCB fabricators (PCBway, etc.). You'll find this project in kicad_board/.