An RP2040-based PC-FX Development Cartridge
Originally published on hackaday.com by Dave Rowntree on 2 November 2024
David Shadoff’s PC-FX Dev Cart is a custom cartridge that allows developers to upload code quickly to the retro NEC PC-FX console. The cartridge uses a Raspberry Pi RP2040 microcontroller and connects to the PC-FX’s FX-BMP slot, originally designed for save data. This port can also be used to boot code, making the Dev Cart valuable for developers exploring the system or testing new applications on original hardware.
The RP2040 microcontroller on the Dev Cart has a dual-core setup, with one core emulating the PC-FX’s 128K x 8 SRAM for the console’s bus interface, while the other handles USB communication. David implemented 74LVC16T245 level shifters to handle the voltage difference between the 5V console and the 3.3V RP2040, and the cartridge is powered through USB rather than the console, ensuring ample power for operation without overloading the system. The board supports rapid code uploads via USB-C, making it convenient for testing code before powering up the console.
To manage the system’s timing requirements, David overclocked the RP2040 to 240 MHz, significantly faster than its standard speed. This increased speed reduces latency between the PIO and CPU core and ensures smooth operation with the console. David has shared the project design in KiCAD, along with extensive PC-FX documentation on GitHub, supporting a growing community of retro NEC console enthusiasts by making PC-FX development more accessible.
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