Hexadecimal keypad with LED display

[Tadeusz Pycio]

The hexadecimal keyboard is a throwback to the past, although built with modern components. The premise of the project was Arduino compatibility, so the processor used is not fully utilised, as the keyboard and display are handled by a special TM1638 chip. A serial port with TTL levels is used for communication (and programming), so it can be connected to any RCBus kit.

[Tadeusz Pycio]

I have uploaded the project on GitHub

[Mark Pruden]

Can I ask the purpose of the keyboard ? i.e. what do you intend using it for ?

[Tadeusz Pycio]

Hexadecimal keypad with display adapted to the serial port used in RCBus/RC2014. It will make it possible to turn such a kit into a Z80 trainer like the KIM-1, CA80, TEC-1D... and that is the purpose I intend to use it for. The redundant design, not making full use of the microcontroller for Arduino compatibility, allows this module to be used for other purposes.

[Mark Pruden]

Thanks for the reply. I had assumed that was the intended purpose. The reason for my query is that had you considered a design with more Key's, apart from the Hexadecimal Digits, you only have 4 keys, which is less than the computers you referenced. To design a UX (key sequences) with just the four keys is harder. I believe the controller has capability for total of 24 keys total, which would give you 8 keys to play with which would give you added flexibility

just my 2cents

[Tadeusz Pycio]

Yes, this project has some limitations related to the assumed size of the PCB, the size of the keys used and the prop between the size of the display relative to the keys. I started my adventure with the Z80 with the CA80 trainer, which in its first version used 20 keys (increased to 24 in later releases) and did not limit the monitor's capabilities. Of course, more keys means more possibilities. In order to increase the number of keys in my design, I would have to reduce the size of the keys while maintaining the assumptions of the low-cost PCB and the display used. I know there are also such 6x6mm buttons with similar caps and this could be a solution. It's worth remembering that in the current design I've used keyboard separation diodes, so you could sacrifice one of those 4 keys to call up alternative functions (similar to the Ctrl, Alt or Shift keys known from PC keyboards).

[Tadeusz Pycio]

The first prototype of a hexadecimal keyboard case.

The next version should already have a filter on the display (if I can find a company that will cut me transparent red Plexiglas with this shape of display hole).

I haven't got the idea of doing a description of the keys yet....

The 6x6x7.3 buttons have arrived so you can try to make another version of this keyboard already with 24 buttons. I'm also thinking of adding other connectors for communication, not only as a serial port, but also an I2C slave and as a simple protocol for the shift registers on the module.

[Tadeusz Pycio]

I have come across a cheap device (educational toy - diy calculator) on Chinese Aliexpress that can be used as a donor of a case, buttons, 7-segment display and TM1638 controller to build a hexadecimal keyboard with display. I think I know what the next version of my project will look like. ;)

[Mark T]

I think I prefer this one, I have a pcb laid out for a PIC14 in one of these, but not ordered yet
https://www.aliexpress.com/item/1005007281626004.html?