Sinclair ZX80 / ZX81 / Z88 Forums

BOOM! Big thanks to mark and those that suggested the diode substitution was the issue with my homemade interface. Spot on. The postie delivered 50x 1n4148's today and we're in business. The prototype wiring is the first time in 35 years and somewhat hilarious. I'm tempted to make the PCB now I know...

Whilst waiting for my interface parts to arrive i spent a bit of time on this. Dr Beep will be horrified that it's compiled with mcoder 2 but I'm still at the point of crashing my machine just trying to print simple characters on the screen in machine code 🙄😂 D7CFD77E-FFD1-43FA-96AA-A9E98AF1EDEB.jpe...

Hi Mark, Perfect. I did wonder and I'd already ordered some 1n4148's just in case so hopefully that will solve my problem. I'm using the zx81 memory mapped version so just the link A to B I hadn't picked up on the switching time difference and the fault feels timing related because both the inputs a...

During my latest testing I wrote a simple basic program to poke 8192 starting at 0 Then increment by 1 (using a let statement) Pause for 30 then poke the new number. Repeat forever. Now I'm getting to 224 everytime before it hangs. I'd be inclined to suspect my wiring if it wasn't for the fact I've ...

So today has been a game of several stages. 🙄 Whilst tidying up the wespi and composite mod wiring I broke the composite mod board. 🤬 I've gone back to the transistor mod temporarily but my TV isn't a big fan. On the upside the new membrane keyboard with the embedded switches arrived from Germany an...

The one I'm starting work on first is the one that seems the easiest for me to understand from both an electrical and programmable perspective which will be a full ttl memory mapped version. It'll have 8 outputs and eight inputs.
We'll see how I go from there.

Initially I'm looking at simply being able to interact with some simple external items such as switches, leds and potentiometers although that may progress if I get the hang of it😂 Initially using basic as I'm still only just starting out with machine code which I understand limits me to a memory ma...

Thanks, unfortunately to the UK that's £70
I don't mind buying it but not at that price

Online sources have failed me.
I'd like to grab a copy of the Downey / Rindsburgh book Timex Sinclair interfacing if anyone can help me out.

So caveated by the fact I'm only a couple of weeks back into the zx81 so I may be well off, my thought was if you're purely talking about making a picture there is probably little difference however if you're showing the outcome of mathematical calculations like a circle or a graph you have 4 possib...