GPIO matrix keyboard

[bobricius]

Hi, would it be possible to connect a standard matrix keyboard to unused GPIO?
need 5+8 IO and 5 more GPIO for arrows+ fire as joystick dsub9 maybe one more button to enter MENU.
I can make a colored PCB that will work separately but can be built into the original ZX.
https://www.tindie.com/products/6521/

[RetroSilicon]

Hi,
Wow, this is indeed a great piece of hardware — especially the versions with a built-in LCD, which could be very useful for development and debugging.
There aren’t many unused GPIOs on the Tang Nano, but for a configuration without external FPGA Companion pins enabled, there should be enough for the keyboard matrix, DB9 joystick, reset, and NMI:
keyboard matrix: 5 + 8 pins
DB9 joystick: 5 pins
reset
NMI

I’ll come back to this topic as soon as I’m done with the current instability issues.

Could you please send me some more technical details about your boards? For example, how is the LCD connected? The Tang Nano has a 40-pin LCD connector, so that could potentially be used, although it would greatly reduce the number of available GPIOs.
Does your board include, or could it include, any I/O expanders or shift registers to reduce the number of FPGA pins required? Otherwise, a Pi Pico could potentially be used as an interface between the FPGA and the keyboard/joystick.

[bobricius]

Thanks for reply,
my philosophy is to avoid shift registers and any other chips. I would like to consult with you about the connection, then I would make a prototype and send it to you so that you can better debug the software, I would be interested in Next, MSX and A800, maybe C64 but for now I am most interested in NEXT and MSX. Even though it is very demanding, it can be completely encapsulated like this https://www.tindie.com/products/6998/

If it were possible, the keyboard would go via GPIO (maybe extra rows for menu and arrows), pwm speaker, maybe SPI display st7789 and USB would be reserved for joystick or external keyboard. You can also write to us directly at bobricius@gmail.com

Thanks for your time