FPGA Spectrum Project

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

Post by ketmar »

eh. "release often, release early!" ;-)

just dump it as it is. everybody had to start somewhere, and we aren't here to make fun of your first attemps. in the worst case you'll get no feedback, which doesn't change the situation much from the current one, i guess. ;-) and in the best case you'll get some valuable hints and maybe some help. it is understandable that you're still learning, and i guess nobody expects the perfectly written and documented code from the beginner. ;-)

tl;dr: if the only thing that worries you is bad code quality, then go on, share the code! there is nothing to be ashamed of.

p.s.: i'm not trying to push you, of course. it is up to you to decide anyway, and whatever you decide will not be wrong.
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zxmicrojack
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Re: FPGA Spectrum Project

Post by zxmicrojack »

https://photos.app.goo.gl/UJf4Aw2q3bGpkF1K6

Some photos of the board - I'm using delta-sigma audio dacs, one single flash device for file system / roms, and one single SDRAM, which already comes on the Altera Cyclone IV eval board. Result is a very simple daughter board. VGA is done by simple resistor DAC, and of course PS2 keyboard. I wanted to have something that a complete novice could throw together. The ZX Spectrum core is nearing it's MVP (48k, 128k, turbo, hyper loading, opus discovery disk, multiface). SDcard has to be <= 2GB for now. File system is simple and proprietary for now. ROMs stored on same device as games / disks.
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zxmicrojack
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Re: FPGA Spectrum Project

Post by zxmicrojack »

Thankyou, @ketmar. I've decided on the strength of these conversations to do a full disclosure. I'll share on gitlab in the next few days. Also I'm creating a electronic form of the schematic - currently it's scribbled on a few sheets of A4 with a few coffee stains on. I had not expected to get anywhere with it - it was just a handy distraction from the lockdown, the empty shelves, the empty streets and the empty schools. The trajectory it took is a equal and opposite reaction to the way I was feeling at the time. Now it's just fun, and to share it will be even better.

Watch this space :)
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zxmicrojack
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Re: FPGA Spectrum Project

Post by zxmicrojack »

I'm working and making good progress on the cleanup. Of course, some horrid things will remain.

Circuit diagram here: hope it is allowed: https://drive.google.com/file/d/1QMU1GS ... sp=sharing.
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zxmicrojack
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Re: FPGA Spectrum Project

Post by zxmicrojack »

And as promised, I'm sharing the source here. I've borrowed bits from other projects from people kind enough to share.

https://gitlab.com/zxmicrojack/fpga-spec

All comments are welcome - try to keep it constructive. All modifications are allowed, but please contribute back to me if you find a bug. If you want to build the hardware yourself, then drop me a line I'll include more step by step info. Really, this board can be put together by people of limited soldering ability, and no fancy equipment other than a soldering iron, a craft knife and a glue gun.

Enjoy, and please get in touch. Also I've added a couple of extra photos showing the new menu screens. Nothing major, just made a bit more neat, and added a spectrum style rainbow in the corner.
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ketmar
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Re: FPGA Spectrum Project

Post by ketmar »

by the way, could you recommend some free textbooks for those who knows almost nothing about fpgas? or, let me be more specific: i can program in asm for various architectures, so i know what bits, registers and such are, and have some rough understanding of how CPUs are working on a lower level. what should i read to proceed to design my own fpga devices? ;-)
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zxmicrojack
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Re: FPGA Spectrum Project

Post by zxmicrojack »

Not sure if I can recommend. My degree was in computer systems engineering, 26 years ago - a mix of electronics and software, so lots of digital electronics and software, and I wrote some tiny amount of VHDL, but dreamed of picking this up in my career. This never happened due to lack of demand in this area at the time, so I went pure software, but with a good understanding of electronics, the hardware guys passed me schematics so I could write bring up code initially, moving onto bigger projects later on. I programmed embedded in many languages with 6-7 different assembly languages ranging from 32 bit down to 8 bit, and recently moved to Java web services 5 years ago. This is my attempt to fill the gap that was never filled in my career.

So, I'm not sure how much of my limited knowledge of HDLs is by osmosis and how much by self teaching. As a first jump - I read this free ebook:
https://www.amiq.com/consulting/misc/fr ... _ebook.pdf

After that I just tried and failed to do simple things for 2-3 months until I got the "hang" of it. Trial and error, but mostly error I would say is your greatest training tool for any thing. However, I'm more than happy to share what I've learned, please just DM, or even build my board, build my code and mess about with it. It's based on this board:

https://www.ebay.co.uk/itm/ALTERA-Cyclo ... SwpBdd5s3s

And if you are able to hold a soldering iron, the daughter board is simplicity itself. As for verilog, things started to go much better for me when I stopped thinking about this as a sequential program, and thought about it as an expression of the digital hardware. In summary, still very much a beginner, but happy to share.
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ketmar
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Re: FPGA Spectrum Project

Post by ketmar »

thank you alot! i know how hard it may be to give a proper list of things to start with when you collected various random knowledge over the years. ;-) i did various embedded programming too, but never touched the hardware side. i know some theory, and know which side of soldering iron is hot, but that's basically it. but i'm not scared to learn new things. ;-)

so thank you for the book! i'll prolly start (slowly) reading it, and we'll see how it will go from here.
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cmal
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Re: FPGA Spectrum Project

Post by cmal »

Very interesting project, although I know almost nothing about hardware and especially fpga. Thanks for posting. I've downloaded the book and will dig into it.
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azesmbog
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Re: FPGA Spectrum Project

Post by azesmbog »

zxmicrojack wrote:
Thu Aug 13, 2020 9:54 pm

https://gitlab.com/zxmicrojack/fpga-spec

All comments are welcome - try to keep it constructive.
I would like to be constructive, but I don't see the project itself ??
Does he already exist or will he only someday ??

Well, about the scheme, constructively)
The keyboard, of course, will work in this version, but it will still be correct to install protective diodes.
Desirable.
but this is a personal matter for everyone.
FPGA inputs are not very tolerant to 5 volts.
Image
Last edited by azesmbog on Fri Aug 14, 2020 9:39 am, edited 1 time in total.
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