picoZ80 Gives Vintage Z80 Machines a Raspberry Pi RP2350B Brain

Drop-In Z80 Replacement Uses RP2350B PIO for Cycle Accuracy

The picoZ80 surfaced on Hackaday on March 23, 2026 — and for anyone who has spent time with vintage computer hardware or followed the Raspberry Pi RP2350B since its launch, it is a genuinely impressive piece of embedded engineering. The project is exactly what its name suggests: a DIP-40 circuit board designed to drop directly into the Z80 processor socket of a vintage machine, replacing the original Zilog Z80 with Raspberry Pi RP2350B silicon while maintaining full electrical and timing compatibility with the host system.

The Technical Challenge: Cycle-Accurate Bus Emulation

The hard part of a Z80 drop-in replacement is not the instruction set emulation itself — that is well-understood territory — but the real-time electrical interface to the host machine's address, data, and control buses. The original Z80 drives and samples these buses with cycle-level timing, and any replacement that deviates from that timing will fail to work correctly with the surrounding logic.

The picoZ80 solves this with the RP2350B's programmable I/O (PIO) state machines — a defining feature of the RP2040 and RP2350 silicon families that has become a recurring tool for exactly this class of problem. PIO state machines run independently of the main CPU cores at deterministic clock speeds, making them ideal for cycle-accurate bus interface emulation. The RP2350B's dual Cortex-M33 cores handle the Z80 instruction execution itself while the PIO blocks manage the timing-sensitive bus transactions that keep the host system happy.

The result is a replacement that, from the perspective of the vintage machine's supporting chips, looks and behaves exactly like a real Z80. The Sharp MZ and Amstrad PCW systems the project specifically targets are known to be sensitive to Z80 timing — passing both is a strong validation of the architecture.

Wi-Fi and Bluetooth via Resident ESP32

The RP2350B handles compute and bus interfacing, but connectivity comes from a co-resident ESP32 on the picoZ80 board. The ESP32 adds Wi-Fi 802.11 b/g/n and Bluetooth 4.2, communicating with the RP2350B via SPI. The practical applications are significant: network storage access, remote debugging, software loading from modern network resources, and Bluetooth peripheral support are all now within reach for machines that originally relied on cassette tape and 8-inch floppy disks.

The board is designed to fit within the physical constraints of the original Z80 DIP-40 package, meaning installation requires nothing more than removing the original Z80 and seating the picoZ80 — no soldering, no hardware modifications to the host system.

Open Source for Personal and Educational Use

All hardware design files — KiCad schematics and PCB layouts — plus the firmware will be released under a personal and educational use license. This is exactly the right call for a project like this: the maker and retrocomputing communities that will use picoZ80 most are precisely the communities that will improve it, port it to additional target machines, and document use cases the original designers haven't considered.

For the growing category of RP2350B-based vintage computing projects, picoZ80 joins a strong open-source ecosystem. The RP2350B's PIO architecture has proven itself the right tool for timing-sensitive hardware emulation work, and the open-source release means the community can build on it directly.

Sources: [Hackaday](https://hackaday.com) (March 23, 2026), [CNX Software](https://www.cnx-software.com) (March 26, 2026), [Adafruit Blog](https://blog.adafruit.com) (March 24, 2026)