I’m a huge fan of modular hardware—clipping components together to create something new is a massive draw for me. Inspired by the Mecha Comet and Leandro Linares’s portable console, I’ve started building my own handheld.

The Concept: Unlike a dedicated gaming device, I want a modular architecture. By swapping the SD card or attaching peripherals, this device should shift from a retro game console to a web browser, an AI Agent, or a media player.

The Hardware (Prototype 1) I’m using the Raspberry Pi 5 for its form factor and port density.

• Compute: Raspberry Pi 5
• Controller: Razer Kishi Pro V2
• Display: MPI3508 3.5” LCD Touch Screen
• Connectivity:
• Controller connects via a mini USB-C to USB-A adapter.
• Screen connects via a short HDMI ribbon cable (intended to be hidden inside a future 3D printed case).
• Software: Recalbox on a 128GB Micro SD.

Current Status Connected to a 5V mains supply, it boots seamlessly into Recalbox. The concept works!

Design Goals

1. Modularity: Must accommodate add-ons.
2. Portability: Pocketable in its smallest form; rechargeable.
3. Stretch Goals: Steam Link/Game streaming and a custom media centre interface.

Current Challenges

• Screen Orientation: To align the USB ports with the Kishi controller, the Pi must be mounted upside down. Consequently, the screen image is inverted.
• Issue: Editing config.txt to flip the screen isn't taking effect in Recalbox.
• Trade-off: Using a cable extension corrects the orientation but wastes internal space needed for the case.
• Power Supply:
• Plan to use 18650 batteries via a 5V breakout board.
• Concern: A single 3300mAh cell likely offers poor battery life for a Pi 5. Might need a dual-cell setup or a hot-swap mechanism.
• Mechanical Design (SD Card):
• The planned bezel (housing buttons/battery) will physically block the SD card slot.
• Need to design a case with a removable back or slot extender to maintain the "swappable OS" feature.

Next Steps I'm sticking with the Kishi for now, as it proves that any USB-C/Bluetooth phone controller could work, making this accessible for other builders. I will focus on solving the screen rotation and finalising a battery solution in the next update.