PS/2 keyboard to keyboard matrix

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Many vintage computers use a keyboard matrix for input. This solution replaces a missing keyboard with a cheap PS/2 keyboard.

fjkraan

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Simple test for correct operation
11/29/2022 at 17:55 • 0 comments
The board and firmware can be tested from the Arduino IDE, right after programming, requiring only a multi-meter:
- Open the Serial Monitor and set the Baud rate to 115200. The prompt "PS2Keyboard to Aster CT-80 matrix V0.6" should appear.
- Type ? <Enter>. The help text should appear.
- Find pin 1 and 2 from the flat-cable header. These are at the top of the header, next to the text "J3".
- Measure the resistance between the pins with an multi-meter. This should be very high, out of reach of most devices.
- Type C00 <Enter> (One letter, two numbers)
- Measure the resistance between the pins. This should in the range of 100 ohm.
- Type O00 <Enter> (One letter, two numbers)
- Measure the resistance between the pins. This should be very high, out of reach of most devices.
The first number is the column, the second the row. The former ranges from 0 to 7, the latter from 0 to F (entry in hex), but only the first eight are wired to the header.