Sinclair ZX80 / ZX81 / Z88 Forums

I've been reading a few things, and some conversations that were had in 2017 about nuclear power station control.... but hey ho.

As I have a number of zeddys in different configurations and I'm not keen on swapping the ZXpand+ constantly on edge connectors, I was wondering if there is a modern Atari interface for the ZX81. Especially ones that didn't require taking over the on-board ROM.

There were some interesting plugboard versions which seemed to emulate the keyboard, but they look like I'd have to go back in time to get one Also the Spectrum Kempston variants, some of which will work on the 81.

Grateful for thoughts and pointers please.

I remember modding my Timex Sinclair 1000 in the mid 80's with a 8255 General Purpose IO chip and memory mapped it to the computer and attaching a DB9 connector to it. I then hacked CornSoft's Frogger and got a digital joystick to work with the game. Google Wilf Wrigter. He had many articles on how to interface to the ZX81 including how to use a joystick. Sadly I don't think his website exists anymore but I did archived it on my home computer. I'll have to see if I have it. If so I'll post it.

Thanks. Anything you could find would be much appreciated.

I'm currently trying to find the PCB for a Spectrum Kempston joystick but I'm having problems interpreting the German. Have downloaded a copy of LibrePCB in the hope that I can learn enough to alter someone elses PCB layout.

I'm fairly certain I have a Kempston interface for the 81 somewhere, which I acquired in a job lot. I have no use for it so if I can dig it out you are more than welcome to it.

Moggy wrote: ↑Thu Mar 14, 2024 2:28 pm I'm fairly certain I have a Kempston interface for the 81 somewhere, which I acquired in a job lot. I have no use for it so if I can dig it out you are more than welcome to it.

Thanks very much. No rush, give me a nudge as and when and we'll sort out postage.

There was no particular joystick interface that was popular for the ZX81, hence there is no real "standard". Just various interfaces that don't have much in the way of software support, most of which were forgotten about long ago.

Kempston produced joystick interfaces for the ZX Spectrum, but used the smaller, hence cheaper ZX81 sized edge-connector socket. As it happens, because Sinclair kept the signals needed for the ZX Printer in the same positions on the ZX Spectrum edge-connector as that on the ZX81 edge-connector, all the required signals for a Kempston joystick interface are present in the correct positions on a ZX81.

Further, because a Kempston joystick interface uses a I/O address, there are no (practical) conflicts to worry about. Hence they "just work". This applies whether you are using a real Kempston joystick interface or a clone / compatible.

However, there is not a great deal of software that was programmed to work with the Kempston joystick interface.

Some software uses the curser keys. Hence some DIY joystick arrangements exist. That is, the joystick is wired to the keyboard matrix.

I can point you to the schematic for my Kempston compatible joystick interface. It's in this similar topic

Mark

JOY81 - Programmable Joystick Interface for ZX81
Can be found in this forum.
https://www.sinclairzxworld.com/viewtop ... ilit=Joy81

@Michelle.

I have found two interfaces for the Zeddy one a Cheetah the other unknown. I do Have a Kempston but this I seem to remember, unlike what Mark describes, has the extra tangs as used on a Spectrum interface.

Anyhow just PM where you want them sending and I'll do the rest.

No charge.

Paul wrote: ↑Thu Mar 14, 2024 3:49 pm JOY81 - Programmable Joystick Interface for ZX81
Can be found in this forum.
https://www.sinclairzxworld.com/viewtop ... ilit=Joy81

Thanks Paul. I had read that, but Kelly's, "last active" came up with just a dash, so I concluded hadn't been around for a while.

Moggy wrote: ↑Thu Mar 14, 2024 4:36 pm Anyhow just PM where you want them sending and I'll do the rest.

That's very, very kind of you. PM sent.