ZX80 / ZX81 Emulator for the Raspberry Pi Pico

[Exile]

Hello, it's me again.
Can you implement a simple video out like our normal zeddies have?
I'm thinking about a simple board or with only SD card, original zeddy keyboard without USB and video out.
More like Sinclair made their computers.
I have no idea if it's possible to give color output without additional chips. Otherwise black and white would be enough.
With video out I mean no VGA or HDMI, just the single RCA jack (cvbs?)
I found this:
https://github.com/guruthree/pico-composite-PAL-colour

Hi Paul. By "normal Zeddie" I presume you mean one that has been modded to composite output, rather than the original UHF

If you want composite out from the existing picozx81 code, the easiest solution is to use an HDMI to composite converter. I tested one after a user requested composite output on TheBackShed forum. The adaptor I used was: https://www.amazon.co.uk/dp/B086BPVS7G also available in Germany as https://www.amazon.de/dp/B086BPVS7G. This generated a good colour composite signal from the HDMI output of a Olimex RP2040PC. It is small enough to mount inside a ZX81 case. It costs £5.99 / €6.71.

I did experiment with B/W composite output a couple of years ago. I already have the code to read the keyboard directly from GPIO. There are pictures in the thread of picozx81 reading the spectrum keyboard matrix. I would recommend keeping the SD Card, picozx81 uses meta data stored on the card to configure to the right set-up for a given program. The popularity of ZXPand shows that people like to load programs without a multi-minute wait!

If you would like to design a pico board with composite output and the connectors for a zx81 keyboard, then I would definitely try to implement the code. However, I will not design such a board myself, I prefer software

[Paul]

I will design a board for that purpose

[virtvic]

Thanks for the reply, Exile. I thought almost as much.
I'm thinking I could take the 13 pin keyboard output and turn it into a USB signal, then plug that into the Pico?
I'm presuming that's what the user on here did with their ZX80 build? I would need to get hold of that circuit / pcb to do that of course?

It's this one here I'm referring to (from Ikjordan / picozx81 GitHub)

[Exile]

I'm thinking I could take the 13 pin keyboard output and turn it into a USB signal, then plug that into the Pico?
I'm presuming that's what the user on here did with their ZX80 build? I would need to get hold of that circuit / pcb to do that of course?

That's correct, although I think in the image you show the user used a different micro to control the keyboard.

I've attached images from https://github.com/ikjordan/ZX81_USB_KBD/issues/1 where a user has used a second pico to control the keyboard. The veroboard circuit is described in the github. There are also more pictures of it in the issue I've linked.

[virtvic]

I have some spare pico clones that I can use for the keyboard ‘controller’

Just found a ready made pcb for the mechanical keyboard https://www.youtube.com/watch?v=BzbwQ3eUMNg