The variant of connecting a ZX Spectrum keyboard as a matrix via 13 cables to the STECCY board has a serious disadvantage: the display together with the blackboard cannot be mounted far away from the ZX keyboard.
For this reason, there is an alternative: The ZX Spectrum keyboard is converted to a PS/2 keyboard. Then it can be connected to the BlackBoard via a longer thin PS/2 cable.
Here the rows/columns are connected to the STM32F103 on a BluePill board as follows:
Columns Lines
--- --- --- --- --- --- --- --- --- --- --- --- ---
Z80 D0 D1 D2 D3 D4 A11 A10 A9 A12 A13 A8 A14 A15
STM32F103 PB3 PB4 PB5 PB6 PB7 PA3 PA2 PA1 PA4 PA5 PA0 PA6 PA7
Pin PB8 serves as an additional column for extensions. Again, an additional button can be placed between PB8 and PA3 to start the STECCY menu.
The image on the right shows the PS/2 Female connector from the front.
Pins to be used on STM32F103 Bluepill board:
| PS/2 | STM32F103 | Remarks |
|---|---|---|
| CLOCK | PB12 | pulled up on STM32F407 |
| DATA | PB13 | pulled up on STM32F407 |
| GND | GND | |
| 5V | 5V |
Here you will find the documentation on how to connect a PS/2 keyboard to the STECCY BlackBoard.