Project: HDMI/DVI out for STFM

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tuxie
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Re: Project: HDMI/DVI out for STFM

Post by tuxie » Wed Aug 29, 2018 9:45 am

Some improvement planned like higher Resolutions? Acceleration ?

Cyprian
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Re: Project: HDMI/DVI out for STFM

Post by Cyprian » Wed Aug 29, 2018 9:58 am

Would be possible to connect it to the ST main ram, or add ram to FPGA, in order to provide additional extended video modes?
Jaugar / TT030 / Mega STe / 800 XL / 1040 STe / Falcon030 / 65 XE / 520 STm / SM124 / SC1435
SDrive / PAK68/3 / CosmosEx / SatanDisk / UltraSatan / USB Floppy Drive Emulator / Eiffel / SIO2PC / Crazy Dots / PAM Net
Hatari / Steem SSE / Aranym / Saint
http://260ste.appspot.com/

troed
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Re: Project: HDMI/DVI out for STFM

Post by troed » Wed Aug 29, 2018 10:14 am

I have a prototype of this and have run it in a 520ST as well as currently trying to interface it in my accelerated doubleST. I do have issues with the latter, I'm currently delaying /DTACK but there are still some weird issues I'm figuring out atm.

The image quality is truly amazing.

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Smonson
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Re: Project: HDMI/DVI out for STFM

Post by Smonson » Wed Aug 29, 2018 10:22 am

Hi guys! :)
tuxie wrote:
Wed Aug 29, 2018 9:26 am
Is this project still in progress ?

What is working ? What is not Working ? Will this project be open ? Or closed ?
It's in progress. It would be "finished" now except that I've been unhappy that scanline tricks commonly used by demos aren't working properly. However, for the three ST video modes, it's working perfectly for me*.

Right now the design of the PCB and the HDMI video generation part of the FPGA are closed, but the Verilog shifter model (a copy of the real shifter reverse-engineered by Ijor) is an open collaboration. https://github.com/smonson78/st-shifter-verilog.

* - I do have one bug left to find: sometimes the screen is shifted right by one pixel (or half a pixel in low-res) which is only noticeable if you're running full-screen with no borders.
tuxie wrote:
Wed Aug 29, 2018 9:45 am
Some improvement planned like higher Resolutions? Acceleration ?
The only impediment to adding more video modes to the shifter is that the ST only supplies 32000 bytes of video data per frame. To implement a 320x200x256-colour mode for example, the speed of the ST would have to be doubled to 16MHz. And as we all know, that's totally impossible.

To be specific: the way this mod works is that it reads each scanline into a buffer, then at the end of that scanline it outputs it to the HDMI port (doubled for low-res and medium-res) while the next line is being read. But it CAN'T store an entire screen frame, it just doesn't have enough memory for that.
Cyprian wrote:
Wed Aug 29, 2018 9:58 am
Would be possible to connect it to the ST main ram, or add ram to FPGA, in order to provide additional extended video modes?
It's connected to the ST main RAM via the same pathway the original shifter connects. In fact it plugs into the shifter socket. It's only designed to replace the shifter with an HDMI/DVI-compatible output method.

That said, only about 8% of the FPGA is used, if there's anything useful that could be chucked in without needing more than a few extra IO pins and 5v-to-3.3v buffers. The FPGA is a Cyclone-II and has about 10KB of ram available in it.

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Smonson
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Re: Project: HDMI/DVI out for STFM

Post by Smonson » Wed Aug 29, 2018 10:43 am

BTW, this is how it's situated inside the ST.
Image
(those wires poking out the right-hand side are just my debug wires)
  • It plugs into the shifter socket, you have to remove the original shifter
  • It also needs one extra wire attached which must be connected to the VSYNC signal
I do want to start building these as soon as possible, but that's countered by wanting it to be as good as it can be.

I'm expecting them to cost about 90 EUR plus postage.

Cyprian
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Re: Project: HDMI/DVI out for STFM

Post by Cyprian » Wed Aug 29, 2018 11:21 am

I would like to buy one.
Jaugar / TT030 / Mega STe / 800 XL / 1040 STe / Falcon030 / 65 XE / 520 STm / SM124 / SC1435
SDrive / PAK68/3 / CosmosEx / SatanDisk / UltraSatan / USB Floppy Drive Emulator / Eiffel / SIO2PC / Crazy Dots / PAM Net
Hatari / Steem SSE / Aranym / Saint
http://260ste.appspot.com/

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sandord
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Re: Project: HDMI/DVI out for STFM

Post by sandord » Wed Aug 29, 2018 11:56 am

Smonson wrote:
Wed Aug 29, 2018 10:43 am
BTW, this is how it's situated inside the ST.
Image
The picture is broken :(

Cyprian
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Re: Project: HDMI/DVI out for STFM

Post by Cyprian » Wed Aug 29, 2018 11:57 am

sandord wrote:
Wed Aug 29, 2018 11:56 am
The picture is broken :(
What do you mean? You can see no picuter?
I see it correctly
Jaugar / TT030 / Mega STe / 800 XL / 1040 STe / Falcon030 / 65 XE / 520 STm / SM124 / SC1435
SDrive / PAK68/3 / CosmosEx / SatanDisk / UltraSatan / USB Floppy Drive Emulator / Eiffel / SIO2PC / Crazy Dots / PAM Net
Hatari / Steem SSE / Aranym / Saint
http://260ste.appspot.com/

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sandord
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Re: Project: HDMI/DVI out for STFM

Post by sandord » Wed Aug 29, 2018 11:59 am

Cyprian wrote:
Wed Aug 29, 2018 11:57 am
sandord wrote:
Wed Aug 29, 2018 11:56 am
The picture is broken :(
What do you mean? You can see no picuter?
I see it correctly
Apparently, it's my browser (I see only a small black icon with a cross). If I open the picture URL (http://smonson.com/unmanaged/atari/20171107_210215.jpg) on a separate tab, it works.

troed
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Re: Project: HDMI/DVI out for STFM

Post by troed » Wed Aug 29, 2018 12:23 pm

So, since I have one (thanks Smonson for letting me beta test and play around with what it can do!) there's one thing I'd like to point out though. It runs off its own 32MHz clock, which means the ST CPU is running at 8.00MHz. That's no problem - most things will work just fine.

However, a real ST runs at 8.01MHz (old STF), 8.02MHz (PAL STFM, PAL STE) or 8.05MHz (NTSC STE). Since the motherboard has a separate clock for the MFP (the "timer chip") in the ST demo coders have for a long time known that they need to compensate for the difference between the timer clock and the CPU clock. This mostly affects the opening of the lower (and maybe top) border in demos.

A CPU clock of 8.00MHz is "unknown" and some demos will simply not work perfectly. I don't want to exaggerate this as an issue, just pointing it out for purists (like myself ;))

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