Zerofrank

FRANK

FRANK is a hardware emulation platform built around the Raspberry Pi RP2350 (Pico 2 modules and RP2350A QFN). RP2040 / Pico still works in FRANK's socket, but in practice only a handful of firmware (mainly the older ZX Spectrum cores) still targets RP2040. Everything modern (IBM PC, NES, SNES, Genesis, the DOOM / id Tech 1 ports, FRANK OS, and so on) is RP2350-only.

It started as a fork of the Murmulator project by Alex Ekb. Over time it picked up extra video outputs, audio paths, USB and WiFi support, and several form factors.

The name comes from "Frankenstein". The board is stitched together from parts of different projects, so the name stuck.

Looking for an older board?

This repository now ships only the boards under hardware/ that are actively maintained. The accessories/ and archive/ directories are gone. Older revisions, retired boards, and accessory adapters such as HDMI2VGA and USB2PS2 live in rh1tech/frank-archive.

Experimental and work-in-progress designs live in rh1tech/frank-lab.

The boards in this repo

Ten maintained boards and one published prototype, each with its own KiCad project, gerbers, BOM and assembly drawings, plus two add-on modules (TurboSound and Hecate) and three retro-CPU boards.

Board	Render	PCB size	Compute	Best for
FRANK Next		99.0 × 53.98 mm	RP2350B + RP2350A, both on-board	Flagship. Two RP2350 dies, on-board ESP8266EX WiFi, CH343P console, three USB-A host ports.
MegaFRANK		149.9 × 99.5 mm	Pimoroni PGA2350 (RP2350B module)	Maximal board — every output plus on-board dual-AY TurboSound, DS3231 RTC and dual power input.
FRANK PGA		99.5 × 83.1 mm	Pimoroni PGA2350 (RP2350A module)	Every output on one PCB, native USB host with multiplexer, ESD-protected.
FRANK		99.5 × 83.1 mm	Raspberry Pi Pico / Pico 2 (socket) + RP2040-Zero	Socketed alternative. Easiest to solder, swap Pico modules at will, USB-to-PS/2 helper on board.
Old Skool FRANK		100.0 × 79.0 mm	Pimoroni PGA2350 (RP2350B module)	The retro-connector board: HDMI and VGA, hardware PS/2, DB9 gamepad. Only 2-layer design, easiest to hand-assemble.
MiniFRANK		85.6 × 53.98 mm	RP2350A QFN, on-board	Compact full-feature board with WiFi, VGA, HDMI and one gamepad port.
FRANK Core 2U		67.0 × 55.0 mm	RP2350B + RP2350A, both on-board	Smallest usable dual-die board. Video, sound, storage and USB only — no WiFi, no RTC.
FRANK Core 2 Proto		55.0 × 55.0 mm	RP2350B + RP2350A, both on-board	Prototype. Core 2U without the USB host side — the dual-die topology at its smallest.
MicroFRANK		32 × 74 mm	RP2350A QFN, on-board	Smallest single-die board. HDMI only, no hardware PS/2 or DB9 gamepad. Keyboards, mice and gamepads connect over the stacked USB host.
ZeroFRANK		65 × 25 mm	RP2350A QFN, on-board	Smallest RP2350A board. HDMI only, USB host for input, on-board flash + PSRAM + I²S audio.
Nyx		51 × 21 mm	RP2350B QFN, on-board	Open-source Pico 2 clone with built-in PSRAM. Drop-in replacement for Pico Plus 2 in the FRANK socket.

The full-size and compact boards use the M2 GPIO layout, so any firmware build for M2 runs on them (subject to the feature differences below). FRANK Next, Core 2U and Core 2 Proto are the exception: they carry two RP2350 dies and firmware must be built for that split, or the slave simply sits idle. Nyx is a compute module — it plugs into the FRANK socket and provides the RP2350B, flash and PSRAM; the FRANK motherboard provides all the I/O.

Comparison: full-size boards

On-board TurboSound (dual YM2149), a DS3231 real-time clock and a DS2401 silicon serial number are unique to MegaFRANK. Old Skool FRANK is the only 2-layer board in the repo, which makes it the friendliest to hand-assembly and rework.

Comparison: compact boards

FRANK Next, Core 2U and Core 2 Proto share the dual-RP2350 architecture: an RP2350B master for emulation and an RP2350A slave for USB host, audio and housekeeping. Core 2U and Core 2 Proto come from a different subsystem generation than FRANK Next — ESP-PSRAM64H memory, a discrete TDA1387T audio chain instead of the TLV320DAC3100 codec, an AMS1117 LDO instead of a switching buck, and no WiFi or RTC. Core 2 Proto is Core 2U minus its host side: same two dies, no hub, no USB-A, no tape input and no power switch.

Retro CPU boards

These are not emulation boards. Each carries a real vintage CPU in a DIP-40 socket, with an RP2350B acting as the chipset — memory, video, storage and I/O. They do not run the FRANK emulation firmware; each has its own chipset firmware.

Board	Render	PCB size	CPU	Notes
XT8086 Alpha		99.9 × 78.0 mm	Intel 8086 (minimum mode)	The earlier 8086 design: PGA2350 module, VGA and composite outputs. Superseded by XT8086 Beta, now in frank-lab.

Modules

Two add-on modules ship alongside the boards:

Module	Render	PCB size	What it is
TurboSound		42 × 79.5 mm	Dual YM2149 / AY-3-8910 sound expansion (socketed DIP-40). Currently supported only by MiniFRANK via its expansion header.
Hecate		53 × 29 mm	Standalone RP2040 USB-to-PS/2 bridge board. Runs the Hecate firmware; presents USB keyboards and mice as PS/2 devices.

Supported software

Over thirty emulators and native ports run on FRANK boards.

Console emulators

PC emulation

Game engine ports

OS and utilities

Murmulator firmware

The original Murmulator project provides additional firmware that runs on FRANK boards as well:

ZX Spectrum cores: ZX Spectrum 48K / 128K / +3e (tecnocat, pico-spec, frut-bat, ZX Speccy P, murmulator), ZX Elf (pico-alf).

Other cross-platform emulators: MS-DOS IBM PC XT 8088, BK-0010 / BK-0011M, Radio 86RK, Macintosh, Atari 800, NES / Famicom / Dendy, Sega Master System / Game Gear, NEC PC Engine / TurboGrafx-16, Nintendo GameBoy / GameBoy Color, Watara Supervision, Atari Lynx, Bandai Wonderswan / Wonderswan Color, NeoGeo Pocket Color, Gamate, Game & Watch / Elektronika.

Tools and applications: MurmulatorOS, Picomite MMBasic, VersaTerm, the original Murmulator bootloader.

Other compatible boards

Most firmware also runs on:

• Murmulator (M1 and M2)
• Olimex PICO-PC (some firmware)
• Waveshare RP2350-PiZero (some firmware)

Getting started

1. Order or fab the PCB (gerbers are in each board's gerbers/ directory).
2. Source the components using the BOM (hardware/<board>/docs/<rev>/bom.html).
3. Solder following the board-specific guide, starting with the smallest passives and working outwards.
4. Flash firmware: hold BOOTSEL on the RP chip, plug USB, release, copy a .uf2 file to the drive that appears (or use picotool load).
5. Insert an SD card with ROMs, WADs or disk images.
6. Plug in a display (HDMI or VGA), keyboard (PS/2 or USB) and gamepad.

For quick switching between firmware, flash frank-kickstart first. It gives you a graphical launcher that re-flashes from SD without touching BOOTSEL again.

PSRAM

Most modern firmware (frank-os, frank-quest, frank-386, frank-genesis, frank-snes, frank-msx, frank-idtech1, frank-doom and so on) needs 8 MB of PSRAM. Some firmware refuses to boot without it: frank-quest installs a custom dlmalloc backed entirely by external PSRAM (drivers/psram_init.c, drivers/dlmalloc.c), because the runtime (heap-allocated game state, decoded resources, mixer ring buffers, font caches) does not fit in the RP2350's 520 KB of SRAM.

How you get PSRAM depends on the board:

• FRANK Next, Core 2U and Core 2 Proto: 8 MB PSRAM per die, both dies on-board. Nothing to do.
• MiniFRANK, MicroFRANK and ZeroFRANK: PSRAM is already on-board (8 MB). Nothing to do.
• FRANK PGA, MegaFRANK and Old Skool FRANK: the Pimoroni PGA2350 module already includes 8 MB PSRAM. Nothing to do.
• FRANK: the socketed Pico 2 has no PSRAM by default. Three ways to fix this:
  1. Pimoroni Pico Plus 2 (recommended). A ready-made Pico 2 with 8 MB PSRAM. Drop it into the socket and you are done.
  2. Build a Nyx, an open-source RP2350B board with integrated 16 MB flash and 8 MB PSRAM. Same form factor as Pico 2, drops straight into the socket.
  3. Solder a PSRAM chip on top of the flash chip of an RP2350 clone. SOP-8 flash chips are mostly only on clones (typically the black boards), not on a genuine Pico 2.

Repo layout

hardware/      Board KiCad projects (frank_next, megafrank, frank_pga, frank,
               oldskool, minifrank, frank_core2u, frank_core2_proto, microfrank,
               zerofrank, nyx), the retro-CPU board xt8086_alpha, plus the turbosound and hecate modules
docs/          Shared component datasheets and assembly notes
software/      Pre-built UF2s. Currently ships Hecate, the USB-to-PS/2 bridge
               firmware for FRANK's on-board RP2040-Zero. Once flashed, a USB
               keyboard or mouse appears on the hardware PS/2 lines.
               Source: https://github.com/rh1tech/hecate

Documentation

Each board and module has its own assembly and usage guide:

• FRANK Next assembly and usage guide
• MegaFRANK assembly and usage guide
• FRANK PGA assembly and usage guide
• FRANK assembly and usage guide
• Old Skool FRANK assembly and usage guide
• MiniFRANK assembly and usage guide
• FRANK Core 2U assembly and usage guide
• FRANK Core 2 Proto assembly and usage guide
• MicroFRANK assembly and usage guide
• ZeroFRANK assembly and usage guide
• Nyx assembly and usage guide
• TurboSound module guide
• Hecate (USB-to-PS/2 bridge) guide

The hardware/<board>/docs/ directories also contain auto-generated BOMs (bom.html) and assembly drawings (assembly.pdf, schematics.pdf) for each PCB revision.

Links

• rh1.tech/projects/frank — project website
• rh1tech/frank-archive — older boards and accessories
• rh1tech/frank-lab — experimental designs

Firmware repositories

Console emulators:

• frank-nes — NES / Famicom (Dendy)
• frank-snes — SNES / Super Famicom
• frank-genesis — Sega Genesis / Mega Drive
• frank-c64 — Commodore 64
• frank-apple — Apple IIe
• frank-msx — MSX / MSX2 / MSX2+

PC emulation:

• frank-386 — IBM PC i386 (DOS, Windows 3.x/95, Linux)

Game engine ports:

• frank-idtech1 — DOOM, Heretic, Hexen, Strife (all-in-one)
• frank-doom — DOOM (standalone)
• frank-heretic — Heretic
• frank-wolf3d — Wolfenstein 3D
• frank-duke3d — Duke Nukem 3D
• frank-prince — Prince of Persia
• frank-digger — Digger Remastered
• frank-quest — ScummVM (AGI, SCI, SCUMM, GOB, KYRA)

OS and utilities:

• frank-os — Full desktop OS with built-in emulators
• frank-kickstart — UF2 firmware launcher
• frank-manul — Text-mode web browser
• frank-netcard — AT modem firmware for ESP-01
• hecate — USB-to-PS/2 bridge for the RP2040-Zero

Author

Mikhail Matveev — software engineer and hardware developer based in Thessaloniki, Greece. Background in software architecture, QA and open-source development. Builds retro computing hardware and writes firmware for fun. More projects at rh1.tech.

License

© 2026 Mikhail Matveev, xtreme@rh1.tech

GPL v3. See LICENSE.