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Forum Index : Microcontroller and PC projects : PICOZX81 - a ZX81 emulator for Raspberry Pi Pico
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| Frank N. Furter Guru  Joined: 28/05/2012 Location: GermanyPosts: 847 |
Dear all, Have any of you tried the "PICOZX81"? This is a ZX81 emulator that runs on the Raspberry Pi Pico: https://www.sinclairzxworld.com/viewtopic.php?f=3&t=5071 https://github.com/ikjordan/picozx81 Apparently it was developed by our member “Exile” - either i have overread that he has developed this emulator or he has kept it quiet until now...  I think this emulator is just great! Many thanks for that!  I was so enthusiastic about it that I developed a keyboard for it (based on this project: https://github.com/ikjordan/ZX81_USB_KBD , also from Exile):     You can find more information about my keyboard (unfortunately only in German) here: https://forum.classic-computing.de/forum/index.php?thread/34553-keyboard-projekt-f%C3%BCr-zx80-zx81-und-oder-emulator/&postID=513583#post513583 Frank |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4343 |
Hi Frank, First I thought the pico on the keyboard was the whole ZX81. But later realized it is the keyboard controller. And it needs a second pico to run the ZX emulator. Volhout PicomiteVGA PETSCII ROBOTS |
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| Frank N. Furter Guru Joined: 28/05/2012 Location: GermanyPosts: 847 |
Hi Volhout, you are right! The pico on the keyboard ist only the keyboard controller. You can use the keyboard on any device as a USB keyboard. But it works particularly well with the PICOZX81. In the picture below, it is connected to a "Waveshare Pico-ResTouch-LCD-2.8" on which the emulator is running. With this cable construction, our USB-Picomite can also be operated WITHOUT soldering. Frank |
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| mclout999 Guru Joined: 05/07/2020 Location: United StatesPosts: 472 |
If I'm gonna spend any time on a spectrum Sinclair. project. It would be on a specky like this. ZX |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6904 |
I still have a couple of real ZX81s. :) All that computing power to emulate a low speed ZX81 and ULA that did everything. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| gadgetjack Senior Member  Joined: 15/07/2016 Location: United StatesPosts: 148 |
I built this 3 or 4 months ago. It does work quit well. I just use the usb keyboard with it. I used the same waveshare board too. Neat little project. A sinclair zx81 was one of my first home computers. Bought the kit and assembled it to get it cheaper back then. Jack |
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| Frank N. Furter Guru Joined: 28/05/2012 Location: GermanyPosts: 847 |
This board runs PICOZX81. Better than running an emulator on a PC... I also have a real ZX81 - but I don't know if it still works. Usually the ULA is now defective or the keyboard is causing problems. Before I get a replacement for the ULA and change the keyboard and then can only load and save via cassette, I'd rather use the great PICOZX81. Frank Edited 2024-12-17 04:55 by Frank N. Furter |
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| cosmic frog Senior Member Joined: 09/02/2012 Location: United KingdomPosts: 289 |
I built this a few months back along with the spectrum version on some prototype strip board. They both work great and cost almost nothing to build. I like the idea of emulating old 8bit computers using the Pico instead of using a big PC. Dave. |
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| mclout999 Guru Joined: 05/07/2020 Location: United StatesPosts: 472 |
I like the project I listed at because it also runs other micros and consoles in different cores. So it's a nice flexible device you can run specky and a growing number of other emulated devices. This video is nice on this device. Video |
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| al18 Senior Member Joined: 06/07/2019 Location: United StatesPosts: 207 |
This has been available on Tindie.com for about 2 years. The GitHub link https://github.com/fruit-bat/pico-zxspectrum Edited 2024-12-17 12:17 by al18 |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9322 |
Does the emulator emulate the 16K RAM-pack? I would expect so. The ZX81 with 1K of RAM, was, basically, useless. The 16K RAM expansion pack was touchy as hell - BREATH near it, and it would cause an intermittent connection, totally crashing the machine. We used to call the ZX81 "The door-stop", cos that was about as useful as it got! I won't go into the HELL that was using a standard audio cassette recorder to attempt to save or load programs.... Despite those issues, it was remarkably popular, even though with just the base 1K of RAM, it was almost dumber then a dumb terminal.  I expect the machine would have been MUCH more usable, had Clive allowed 16K of on-board RAM, but Clive was well known to squeeze every penny - to the extent that the PCB for the ZX81, had no soldermask, only a solder-wave coating! Saves a few cents per unit!  Smoke makes things work. When the smoke gets out, it stops! |
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javavi Senior Member Joined: 01/10/2023 Location: UkrainePosts: 296 |
I once posted a port of this ZX-Spectrm project for the PicoMite VGA board here, but few people were interested in it at the time. Can I ask the author to make a configuration for the PicoMiteHDMI board!? |
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| Frank N. Furter Guru Joined: 28/05/2012 Location: GermanyPosts: 847 |
Yes, the ZX81 is terrible and yes, the PICOZX81 also emulates the memory up to 48K! Nevertheless, it is a piece of contemporary history and I find it very interesting! Can anyone tell me how to stop this program? It comes from the manual - I haven't found a way yet... 10 PLOT INT (RND*64),INT (RND*44) 20 INPUT A$ 30 GOTO 10 Frank |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6904 |
Perhaps I've been lucky. Although I've had both ZX81 and Speccy, and used all sorts of things plugged into their expansion ports, I've rarely had problems with either. Obviously, I had to be careful with them and not let the system wobble too much, but neither were really bad. Likewise, if I couldn't load a tape it was very likely that none of my friends could either. Some cassettes were duplicated badly or just used poor quality tape. My final episode was the Speccy, with three microdrives, running a Teletext-style bulletin board called MIXTEL (Mick's TELephone). :) I think I only ever had two microdrive cartridges die, which wasn't a disastrous failure rate considering the reports from others. If I want to play on old machines now I always use emulators. I've no interest in most of them now as, to be honest, I find every one to be so limiting that I either get bored or give up entering line numbers. The only one that I really miss though is the original keyboard Speccy as IMHO the compromises made were all in the right places. I could actually program on that without going nuts. The worst, which I was glad to get rid of, was the Commodore 64. I didn't like that at all and I wouldn't even consider it worth loading an emulator. For some cool stuff look at Grant Searle's pages for his Multicomp design that runs on a FPGA. It's a building-blocks computer. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9322 |
"SHIFT+BREAK" seems to come into my head to stop a running program, but this is going A LONG way back in my memory. I'm guessing everyone on this forum has seen the "Micro-men" movie? It's well worth a watch if you haven't, as it documents Sinclair computers and Acorn etc. One thing I DID really like about the ZX81, was the whole keyword idea, where you could just press one "Key" on the membrane keyboard, and it would insert the entire BASIC command with the touch of just one key. That was a nice idea, and did make experimenting with the base 1K model, easy. Programs could be written quite quickly using that idea. Smoke makes things work. When the smoke gets out, it stops! |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4343 |
Grogster, I owned a ZX81 once, as part of a heritage. And yes, it was too limitted. But now adays I might find it a challenge to work with such limitations. That is why I alsway take part of the MMBasic programming challenge. Limitted resources, and see what you can do with them... One thing I remember seeing was a way to safely control external devices with a ZX81. They glued (yes!) LDR's (light dependent resistors) to the monitor screen (blue-tak). And by lighting sections of the screen they controlled relays. I found that so ingenious I remebered. Nothing with edge connectors, and 74LS374 latches, address selectors, opto couplers...not...via the monitor itself. Volhout Edited 2024-12-18 17:38 by Volhout PicomiteVGA PETSCII ROBOTS |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2176 |
A 2D opto-coupler array. Clever! |
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| Frank N. Furter Guru Joined: 28/05/2012 Location: GermanyPosts: 847 |
Thanks for your reply! Unfortunately, this only generates the “£” sign.  Without SHIFT, unfortunately only SPACE. You can try this out online very nicely with https://www.zx81stuff.org.uk/zx81/jtyone.html. Yes, but I often have to search for several minutes for the right button...  @Grogster: You are an admin - can you perhaps draw Exile's attention to this thread with an e-mail? I have sent him a PM - so far he has not responded. I would like to provide him with the Gerber files for the keyboard... THANK YOU!!! Frank |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9322 |
Re: Screen and LDR concept, yes, very clever indeed!  @ Frank - OK, I will flick him an email and link him to this thread. EDIT: Done. Hopefully, he will pop up on this thread. Edited 2024-12-19 08:38 by Grogster Smoke makes things work. When the smoke gets out, it stops! |
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| Frank N. Furter Guru Joined: 28/05/2012 Location: GermanyPosts: 847 |
@Grogster: Thank you very much!!! That's a very clever concept! I have an old TAN generator who works in a similar way... Frank |
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