The keyboard is the part you touch every time you use the machine, so keeping it matters as much as keeping the shell. A replacement keyboard might be easier, but it would immediately make the result feel less like a VAIO P.

Our goal is to make the original keyboard appear to the CM5 as an ordinary USB device.

Original Japanese Sony VAIO P keyboard and pointing stick removed from the laptop
The Japanese keyboard, pointing stick, palm rest, and front buttons form one tightly packaged assembly. Keeping the whole deck preserves both the look and the typing position of the original machine.
Sony VAIO P keyboard deck underside and lower chassis showing the original ribbon cable path
The keyboard deck is thin, rigid, and shaped around the VAIO P shell. Keeping it means the new controller has to respect the original ribbon path and connector location.

Connector problem

The keyboard cable ends in a 50-pin, 0.4 mm pitch connector that mates with a Panasonic AXK750147G-style socket. It is far too fine for jumper wires or a breadboard.

So the first PCB is deliberately simple: a breakout that will

  • hold the original connector securely
  • fan all 50 lines out to test points or 0.1-inch headers
  • let us trace the matrix with a multimeter
  • protect the original cable while we probe it

It is not the final controller. It is the tool that makes the keyboard understandable.

Matrix scanning

The current controller plan is an RP2040 running CircuitPython and KMK. It will scan the VAIO P matrix and report the keys as standard USB HID input.

That keeps the CM5 side simple and lets the original keyboard behave like a normal peripheral.

Keyboard matrix PCB laid into a blue Sony VAIO P keyboard shell for USB HID controller planning
The matrix is the useful map. Once rows and columns are identified, the RP2040 firmware can turn the original VAIO P keyboard into a standard USB HID device.

Bring-up checklist

Before connecting the keyboard controller to the CM5, the keyboard side should be tested by itself:

  • inspect the connector under magnification
  • check for solder bridges
  • map rows and columns with a multimeter
  • confirm every key closes the expected matrix connection
  • test a minimal KMK firmware build
  • verify USB HID output on another computer

Pointing stick

The pointing stick deserves its own bring-up step. It is part of the VAIO P experience, but mixing it into the first keyboard test would make debugging both systems harder.

We will prove the key matrix first, then decide whether the pointing stick belongs on the same RP2040 or on a separate interface.