FPGA Spectrum Project

For experts to discuss very technical stuff and newbies to ask why the Spectrum they bought off ebay doesn't work.
zxmicrojack
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FPGA Spectrum Project

Post by zxmicrojack »

Moved by PJ

Hi all,

Wondered if this was the right place, but during lockdown in the UK, I thought I would have a try at FPGA programming which is something I've always wanted to have a go at - saw all the projects around, so thought, I can make some simple and cheap hardware based on a cheaper FPGA eval board, and then try to use some of the MiSTer sources available. The board I brought up, was all fine, but the existing codebases wouldn't work for me as I had based the whole idea on a single SDRAM device, and a single SD card for BIOS.

I've ended up re-engineering a ZX-Spectrum 48/128 with Multiface 1 / 128, and with Opus Discovery single disk drive, and a menu system to load tapes and disks from SDcard. Also I've patched loaders to give us turbo (4x loading tape speed) and recently almost instant loading by patching the ROM and adding a direct read IO port. This has been tremendous fun, and I intend to continue improving ZX spectrum or maybe moving to other old devices, maybe BBC etc.

The thing is then, I've based my hardware on a sub 35 GBP board and a simple home made hardware daughter board I made for less than 10 GBP, and it mostly works - I have a few issues, not every game works yet, some oddities, some bugs etc, but then I thought maybe someone else could get a kick out of it, maybe if I clean up and share the hardware design, verilog source, and bootstrap source code then others could make their own device, run either my microcode or make their own and share it. Maybe we could make between us a cheap board, case, or other developments.

What do people think? Would someone be interested in sharing my project, perhaps developing it further in the spirit of open source/hardware?

Cheers,
M.
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azesmbog
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Re: FPGA Spectrum Project

Post by azesmbog »

Lay out the sources, why pull the cat by the tail.
If anyone is interested, they will compile and try.
But better than MiSTer, or cheaper than Uno - no longer do. The "Next" one is a separate song, for which I will not say anything.
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zxmicrojack
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Re: FPGA Spectrum Project

Post by zxmicrojack »

Trying to gauge if it's worth the effort of documenting and sharing properly - something I will not gain anything from. Pulling the cat by the tail, not even sure what that means. But thanks for your reply.
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ketmar
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Re: FPGA Spectrum Project

Post by ketmar »

zxmicrojack wrote:
Wed Aug 05, 2020 4:51 pm
Pulling the cat by the tail, not even sure what that means.
google translate. ;-) that first line roughly means "oh, just publish the sources as they are, why not?"

@azesmbog try to avoid proverbs and such, it's usually hard to properly translate 'em. ;-)
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azesmbog
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Re: FPGA Spectrum Project

Post by azesmbog »

This is an idiom about a cat :)
Something like - Don't keep me in suspense!
If your project is for Altera or Xilinx - then you can lay out without documentation, as it is, if under Latice - then it would be necessary with a description :)
And of course, how to boot from an SD card.
If it's not too confused and tricky, then what problems can you repeat on other devboards? A lot of them.
And I wonder what you expect to get :) Besides the fun.
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zxmicrojack
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Re: FPGA Spectrum Project

Post by zxmicrojack »

I must admit I'm not familiar with that one. Problem is I've been a software engineer for 23 years, what I consider good to share is definitely not what I have at the moment. Documentation, I wouldn't dream of sharing stuff without. But I see your point. I'll do a bit of clean up then start to share. I'll share some photos and stuff in due course, thanks!
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azesmbog
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Re: FPGA Spectrum Project

Post by azesmbog »

zxmicrojack wrote:
Wed Aug 05, 2020 6:36 pm
Problem is I've been a software engineer for 23 years
The problem is that I'm not a programmer at all, ketmar won't let you lie,
but I will distinguish VHDL from Verilog, but I don't like modules on SystemVerilog, it's hard for me to translate them back to Verilog :)
Let's wait.
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ketmar
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Re: FPGA Spectrum Project

Post by ketmar »

azesmbog wrote:
Wed Aug 05, 2020 7:29 pm
ketmar won't let you lie,
i.e. "ketmar knows that". all hail automatic translators! ;-)

(as written, it means "ketmar won't let zxmicrojack to lie". this is definitely not what expected. ;-)
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akeley
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Re: FPGA Spectrum Project

Post by akeley »

@zxmicrojack what you did sounds very interesting and impressive, skills wise.

But to be honest, I'd much rather see talented FPGA devs join forces and concentrate on one platform. At the moment this already very niche retro zone is quite fragmented - there are many different boards and projects (MiST, MiSTEer, Sidica, ZX Uno/ZXDoS/ ZX ???, some others I don't rememebr names of.) Sure, lots of the code is shared but there are also a lot of unfinished cores.

MiSTer is the second priciest of the aforementioned FPGAs but also has the biggest potential and community. Why not jump on its repos and try to contribute there? The microcomputer cores are pretty good already but could still benefit from and attention of a skilled dev.
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zxmicrojack
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Re: FPGA Spectrum Project

Post by zxmicrojack »

@ketmar I understood perfectly what @azesmbog meant - even the pulling of the cats tail I should have guessed at. Maybe western hemisphere arrogance or stupidity in me. I see your work already in the community and it makes me even more nervous about sharing. Though you will be happy to know other than the code I borrowed, it's almost entirely in verilog. Only started verilog in March, and it shows - some of the earlier code is quite terrible.
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