Pi1541 Disk Drive Emulator PCB with 35KB RAM Expansion for Commodore VIC-20

This is the third and most advanced variant—it combines two independent functions in one cartridge: RAM expansion (identical 35KB as in the previous project) and Pi1541 disk drive emulator based on Raspberry Pi Zero.

RAM section (35KB, 27+8): The same components as in the previous version—SRAM 62256 (32KB, DIP28), SRAM 6264 (8KB, DIP28), 74LS21 logic chip for address decoding, bank configuration via DIP switch.

Pi1541 section: Raspberry Pi Zero as controller, support for D64 and .PRG files, 0.96" OLED display, 4-channel bidirectional level shifter, 6-pin DIN connector for drive connection. The author credits the original Pi1541 project by Stephen White and RAM expansion schematics by Ruud Baltissen—the same sources as in the previous project.

Key feature: Both sections can operate independently or together, switchable via JP1 jumper. Described as an "Easy DIY project"—through-hole components, marked on the PCB, easy to solder; tested on NTSC VIC-20.

Pi1541 is a real-time, cycle-accurate 1541 drive emulator—an alternative to SD2IEC. It's worth noting that this directly aligns with your own Pi1541-III product—this project is an independent implementation combining a similar concept (Pi1541 + RAM expansion) in one VIC-20 cartridge, which could serve as an interesting reference or source of inspiration for your product line development.

Project:
https://www.pcbway.com/project/shareproject/COMMODORE_VIC_20_Pi1541_35KB_27_8_RAM_EXPANSION_CARTRIDGE_0c9e08a6.html