ZX PicoIF2Lite Discussion

[pollito]

@TomD I hope you don’t mind, but I thought it would be good to open a separate thread for your PicoIF2Lite as I’ve had a chance to have a play around with it now, and have some questions. And, I guess others may have too.

First of all I’ll link to the project in case anyone reading this is looking for it: https://github.com/TomDDG/ZXPicoIF2Lite

The first question I have is regarding compatibility. Does the device also work with +2A/B and +3 Speccies? The reason I ask is because I believe they have more ROMs than the +2 and below.

Secondly, regarding bugs and enhancement requests, would you prefer to discuss them here, or create Issues on the Github project page?

[TomD]

@TomD I hope you don’t mind, but I thought it would be good to open a separate thread for your PicoIF2Lite as I’ve had a chance to have a play around with it now, and have some questions. And, I guess others may have too.

First of all I’ll link to the project in case anyone reading this is looking for it: https://github.com/TomDDG/ZXPicoIF2Lite

The first question I have is regarding compatibility. Does the device also work with +2A/B and +3 Speccies? The reason I ask is because I believe they have more ROMs than the +2 and below.

Secondly, regarding bugs and enhancement requests, would you prefer to discuss them here, or create Issues on the Github project page?

I've not actually tried it on a +2A/B or +3 only 48k and 128k toastrack. It should in theory be ok but maybe the edge connector differences will cause issues. I'll have a look.

On the enhancement/bugs please use either as I will check both regularly, I'm probably on here more than GitHub though, so this forum maybe better.

I've also created a new version of the interface, one that removes the need to load up the Pico firmware with ROMs. Instead it uses a micro SD Card reader. Only downside is the joystick connector has gone, however, my ultimate aim is to use the interface with USB or Bluetooth controllers with a Pico W. Very early days on development and I may well add the 9pin joystick port back in if I can't get it working

TomD

[pollito]

If you could let me know of any potential dangers to my +2A before I plug it in, that would be greatly appreciated! If it works, maybe it could be a way of playing incompatible games on the machine?

I'm absolutely loving having the 128K menu on my 48K Speccy. I'm now considering changing the internal ROM to make it permanent!

The SD card is a really cool idea, but it's a shame you had to sacrifice the joystick port, as I really need one. I think it's the curse of the 48K owner! I didn't think it was attached to the Pico, though, I was under the impression it bypassed it, and went straight to the edge connector?

Recently microcontroller boards like the Pico have really proven themselves in the retro computing world. Ingenious devices like your PicoIF2Lite, the SidecarT for the Atari ST, and the PicoMEM for vintage PCs are great examples of this.

In the other thread, the potential of wifi was discussed that could work with a Pico W, and the RP2040's second core. I'm not sure if it would be possible, but I was thinking the wifi could be used in conjunction with a small web server. As well as providing a TCP/IP stack to the Speccy, much in the way that the M4 board does for the Amstrad CPC, Z80s and SNA files could be uploaded via a web browser. The web server could convert/compress them on the fly, storing them either on the SD card, or in the internal flash.

I also thought that maybe the button on the top of the device, rather than going straight into the ROM explorer, could bring up a top-level menu which could have items like a hack tool for entering Multiface-type cheats, a configuration tool for the wifi stack, an option to enter the ROM explorer (of course!), and maybe even a tool for taking, and loading snapshots to/from the Speccy.

Anyway, this is just me brainstorming, and I'm not even sure if it these things would be technically possible. I am looking forward to building the next version of your board once you release the designs, and I really hope you can find it in your heart to try and squeeze the joystick port back on at some point. I will log a few (realistic) enhancement request on Github over the next few days, and let you know here if I run into any difficulties.

Nick

[TomD]

The SD card is a really cool idea, but it's a shame you had to sacrifice the joystick port, as I really need one. I think it's the curse of the 48K owner! I didn't think it was attached to the Pico, though, I was under the impression it bypassed it, and went straight to the edge connector?

It does (via some diodes) go straight to the edge, I just ran out of space on the board I can rearrange or just make it larger to accommodate though. The other issue with the way I wired up the joystick (using the Shadow of the Unicorn set-up) was it will never work with autofire joysticks, although that might not be a massive issue. I wanted to try getting USB & Bluetooth working as that would open up the use of the latest controllers with loads of buttons.

Recently microcontroller boards like the Pico have really proven themselves in the retro computing world. Ingenious devices like your PicoIF2Lite, the SidecarT for the Atari ST, and the PicoMEM for vintage PCs are great examples of this.

I just watched Adrian's PicoMEM video and was amazed how much FreddyVRetro got out of a single Pico. This definitely inspired me to get my new board working. I've already created the Microdrive replacement (https://github.com/TomDDG/ZXPicoMD) and a joystick interface (https://github.com/TomDDG/ZXPicoJoy) and love this little board.

In the other thread, the potential of wifi was discussed that could work with a Pico W, and the RP2040's second core. I'm not sure if it would be possible, but I was thinking the wifi could be used in conjunction with a small web server. As well as providing a TCP/IP stack to the Speccy, much in the way that the M4 board does for the Amstrad CPC, Z80s and SNA files could be uploaded via a web browser. The web server could convert/compress them on the fly, storing them either on the SD card, or in the internal flash.

Definitely on the to-do list, I also want to add this to my Microdrive emulator.

I also thought that maybe the button on the top of the device, rather than going straight into the ROM explorer, could bring up a top-level menu which could have items like a hack tool for entering Multiface-type cheats, a configuration tool for the wifi stack, an option to enter the ROM explorer (of course!), and maybe even a tool for taking, and loading snapshots to/from the Speccy.

This would need the NMI wiring up which it isn't at the moment. With my other interfaces I went with an OLED screen on the actual board rather than use the Spectrum. I just find this easier and enables changing of settings, cartridges etc... independently. Probably not great for cheats though, so another thing for the list.

[pollito]

Hi @TomD,

I hope you are well. I have been doing a lot of testing, and have had a lot of fun along the way! Most snapshots I download from various sources around the internet work fine with the PicoIF2Lite, but I have trouble getting the ones that I create with FUSE to work (even though the machine is set up to be a 48K model). Also, some of the downloaded ones have strange behaviour, for example Jet Set Willy keeps jumping and jumping once the game has started. All of those problematic snapshots seem to work fine under FUSE.

Would you like me to upload the problematic snapshots somewhere to see if you get the same behaviour, and maybe can work out what is happening? If so, where would be a good place?

I had another idea - how about a Pico-based device that offers mass storage, and is compatible with the DivMMC / DivIDE devices, so that it can be used with the +3e ROMs? Those mass storage devices are very cool, but are quite expensive because they use CPLDs. CPLDs also seem to reach their EOLs after only a few years, and those devices then need to be redesigned for new CPLDs. The Pico, on the other hand, is very cheap by comparison, and shows no signs of becoming obsolete anytime soon.

Cheers,
Nick

[TomD]

Hi @TomD,

I hope you are well. I have been doing a lot of testing, and have had a lot of fun along the way! Most snapshots I download from various sources around the internet work fine with the PicoIF2Lite, but I have trouble getting the ones that I create with FUSE to work (even though the machine is set up to be a 48K model). Also, some of the downloaded ones have strange behaviour, for example Jet Set Willy keeps jumping and jumping once the game has started. All of those problematic snapshots seem to work fine under FUSE.

Would you like me to upload the problematic snapshots somewhere to see if you get the same behaviour, and maybe can work out what is happening? If so, where would be a good place?

I had another idea - how about a Pico-based device that offers mass storage, and is compatible with the DivMMC / DivIDE devices, so that it can be used with the +3e ROMs? Those mass storage devices are very cool, but are quite expensive because they use CPLDs. CPLDs also seem to reach their EOLs after only a few years, and those devices then need to be redesigned for new CPLDs. The Pico, on the other hand, is very cheap by comparison, and shows no signs of becoming obsolete anytime soon.

Cheers,
Nick

The issues you are facing are likely to be Kempston joystick related. A lot of snapshots created had Kempston interface selected so when you load them on a real machine which doesn’t have that interface you get strange results, such as Miner Willy jumping around like fire button is being pressed.

Try and take some snapshots with kempston disabled in Fuse and if they still don’t work then let me know and I’ll figure out what is the best way to get these to me for testing.

I think a Pico based divmmc is the ultimate aim or even an Interface 1 type device giving access to SD Cards or real Microdrives. Biggest issue is the number of pins available on the 2040, meaning you need more than one which adds cost. I’m experimenting with using pins for multiple I/O to see if I can get around that.

TomD

[pollito]

Thanks, Tom, I will try what you said regarding the Kempston, and let you know the result.

I'm still very much an electronics newbie, but I'm starting to work on a backplane as I've realised that I need more than one expansion for both my Speccies in order to achieve what I want to do with them. I've seen existing solutions, but have not been happy with any of them for one reason or another. Of course, if and when I have made progress, I will upload the results to Github. I may start a thread here too after I've done some prototyping.

Given that, I don't see any problem with having one card that does ROMs/snapshots and MicroDrive emulation, another one that does mass storage and maybe floppy emulation, etc. I agree, however, that it is good to squeeze every ounce out of the Picos involved