ST HDMI Out

[SainT]

I've finally got something vaguely working on my HDMI out project! Its just displaying a single bit of blue, but I now have something I can recognise as the ST desktop. Hurrah!

Now to redesign the level converter board into something which is less of a mess and can plug directly into the FPGA board for the second prototype and get the scan doubling sorted. The nice thing is, this will also handle hi-res as well. All the joys of proper ST hardware right on your LCD flat screen with pixel perfect accuracy!

[Dal]

Put me down for 2 of these when they go into production. Nice project.

[DarkLord]

What are the reqs going to be for this, as in power supply, size, etc? Does the ST
have to have a modulator already, etc,...

Most importantly, will it fit inside a STacy?

[SainT]

The final board should be pretty small. It just needs to have a small FPGA and a level converter chip on-board plus a few other bits and pieces and an HDMI connector. Power requirements will be low. I don't have the STacy schematics to hand, but I think it will work. It just requires connections into the resistor ladder which outputs the RGB / mono to the monitor port. This output could also be used to drive a colour LCD panel quite easily... The FPGA is outputting HDMI format signals over LVDS, so it wouldn't be a huge deal to output LVDS direct to the flat panel.

I don't actually have a whole STE at the moment to figure out where the board is going to fit -- although I've just bought one from eBay. So once I have a case again I'll see where it will fit. It will work in the STFM or STE fine, will just need two different connector boards which fit over the resistor ladder output from the shifter with the correct number of lines out.

Messing with the STacy will be another project for the future. I have a couple of STacy motherboards I want to get working, but will need to make up the daughter cards on FPGA as I only have the main board.

Sadly HDMI out wont work on the TT as Atari put the DAC inside the shifter in the TT, which is a real shame. The video out on my TT through the analogue VGA is total poo!

However it will work on the Jaguar!

I have many things I want to add an HDMI port to...

[Scarlettkitten]

Sounds like a nice project

[nerotik]

I am very interested in this project. So you are using an FGPA to be able to make this all possible, nice. So I hope that it is going to be low cost solution to be able to get our Atari ST/e Computers on the big screen over HDMI. Awesome. I would love to know some more about the fundamentals of this...

[DarkLord]

Wow, this sounds good - not pressing or anything, but do you have a "rough"
timetable for this?

A "guesstimate" would be fine.

PS well, in retrospect I guess that's pretty inane - hard to guess on something
like this.

[SainT]

The timeline is completely unknown, sadly! I'm fitting in doing this board in-between work and having two young kids, so I really don't get a lot of time to work on it. Although now I have *something* working, it should speed up a bit. I've spent many weeks arsing about in the evenings just trying to get RGB signals level converted into the FPGA and stable, all of which is just down to the fact I'm learning everything as I go along. I've got no background in electronics, and there's a whole lot about electrics I had no concept of until I started this. However I'm a techy coder type by trade, so once I've got a load of signals coming into the FPGA all nice, then the VHDL coding part is something that I'm a lot happier with...

I'm not sure about cost yet. I'm using a little £14 FPGA board from China and will need a couple of level converters (one for video and one for STE digital audio), an ADC for the YM audio, an HDMI repeater to turn the LVDS lines into something a little more universally friendly for HDMI TV's and monitors and an HDMI connector. So probably not more than about £10-15 worth of bits. But then there's getting PCB's made (which actually looks reasonably cheap from China) and populating them.

As I said I'm learning all this as I go along, so we'll find out.

Once things are running on a more complete prototype, I'll see if anyone with more experience in this stuff is interested in helping make a batch of final boards.

The fundamentals of this project for video out are relatively simple, really. HDMI is just sending digital RGB and clock data to a monitor -- so if you can get digital RGB and a clock signal from the motherboard, it doesn't take much effort to squirt this data over HDMI. One issue is that you have to use a standard 50Hz mode to get the monitor to recognise it -- in this case 576p (720x576). All sync data is generated by the FPGA and the ST video data is inlayed into the sync signals.

Getting audio working will be a good challenge in itself. The audio packets are transmitted during blanking periods in the video data. I've not looked into this in any detail yet, but it looks like it'll be fun as I'll be writing the audio part from scratch based on some VHDL source I found on the web for the video out.

[BoNuS]

The timeline is completely unknown, sadly! I'm fitting in doing this board in-between work and having two young kids, so I really don't get a lot of time to work on it. .

Sounds like a good project but with the above "constrains" I know that it could take a while It's the same here, sometimes not even enough time to answers mails.
But good luck, if it works out put me down for one ! It's getting a bit crowded here with all the old SC1224's and SC1435 I have to keep just for he ST's.

[SainT]

Haha, yeah, old CRT's are a bit bulky and even RGB scart out is far from great. I'd not used a CRT for many years, and it was actually getting an SC1224 hooked up to my ST which made me realise I needed an HDMI port on the back!

I've got endless plans for modifying the ST... replacing the WD1772 (SUSKA project is great for this) to do floppy emulation and also raw floppy backup... adding an ACSI CF hard drive... reading the floppy images direct from the ST HD... replacing the SIMMs with FPGA controlled SRAM... adding a USB port for direct memory access to the running ST and then streaming the live video data over USB...... the list is fairly endless! Sadly my time isn't...

HDMI out is by far the most useful project though.

[DarkLord]

Well, I hope you don't run into many problems. If you've followed any of the
threads on this subject (and there are *many*), you'll see that there has been
a whole lot of discussion, a multitude of projects started, and to date, not even
-1- single universal product that works, across a variety of ST's and monitors/LCDs.

So we're all in your corner pulling for ya.

[BoNuS]

Haha, yeah, old CRT's are a bit bulky and even RGB scart out is far from great. I'd not used a CRT for many years, and it was actually getting an SC1224 hooked up to my ST which made me realise I needed an HDMI port on the back!

I've got endless plans for modifying the ST... replacing the WD1772 (SUSKA project is great for this) to do floppy emulation and also raw floppy backup... adding an ACSI CF hard drive... reading the floppy images direct from the ST HD... replacing the SIMMs with FPGA controlled SRAM... adding a USB port for direct memory access to the running ST and then streaming the live video data over USB...... the list is fairly endless! Sadly my time isn't...

HDMI out is by far the most useful project though.

My advise: Finish 0ne after the other and don't start them all at the same time. Cause then none of the will see the finish, personal experience

[BoNuS]

Haha, yeah, old CRT's are a bit bulky and even RGB scart out is far from great. I'd not used a CRT for many years, and it was actually getting an SC1224 hooked up to my ST which made me realise I needed an HDMI port on the back!

I've got endless plans for modifying the ST... replacing the WD1772 (SUSKA project is great for this) to do floppy emulation and also raw floppy backup... adding an ACSI CF hard drive... reading the floppy images direct from the ST HD... replacing the SIMMs with FPGA controlled SRAM... adding a USB port for direct memory access to the running ST and then streaming the live video data over USB...... the list is fairly endless! Sadly my time isn't...

HDMI out is by far the most useful project though.

My advise: Finish 0ne after the other and don't start them all at the same time. Cause then none of the will see the finish, personal experience

[SainT]

My advise: Finish 0ne after the other and don't start them all at the same time. Cause then none of the will see the finish, personal experience

Hehe, yes, I only intend to concentrate on one hardware project at a time.

It's quite a nice change from the day job as it's a whole different set of problems to solve.

The only thing I'm not keen on is drilling dozens of tiny little sodding holes for through parts and headers! If only one-off commercial PCB prototyping was just a little cheaper...

[alanh]

Very nice indeed. Looking forward to your progress !

[SainT]

I don't suppose anyone knows where I can find an example HDMI data packet with parity bytes correctly set?

It seems to be easy enough to generate the CRC / parity byte for each section of the packet, but I've not been able to find any example data to see if what I am generating is actually correct...

[alexh]

We talking about an example with BCH ECC for the audio packets? I could capture some with the analyser at work and send you some screen grabs.

[SainT]

We talking about an example with BCH ECC for the audio packets? I could capture some with the analyser at work and send you some screen grabs.

You were next on my list of people to nag.

Funny you should mention an analyser -- I found some screen shots from an HDMI protocol analyser at lunch time which have some example data and BCH ECC bytes shown. So I'll see how my ECC generator works tonight.

I'll take you up on that offer and give you a shout for some specific audio packet grabs if I get stuck further down the line!

And in-case anyone randomly stumbles on this thread looking for sample HDMI data, then here's some data from an AVI Info Frame --

HB: 82 02 0d e4
SP0: 99 00 08 00 04 00 00 d4
SP1: 00 bf 05 00 00 01 05 41
SP2: 00 00 00 00 00 00 00 00

Edit: CRC generation IP written and tested!

[StickHead]

Wow! This is incredible, and exactly what I need! Great work sir, please put me on the list for a day one purchase whenever they are ready!

[SainT]

I got something quite cool working last night.

I can run my FPGA simulation which outputs the HDMI stream, take the resulting waveform file and run it through a custom converter program to convert it to a formatted binary dump of the stream. You can then read this with an HDMI protocol analyser and see precisely all the packets of data being output and whether they make any sense. So I can now write some HDL to output all the suitable HDMI packets and actually see where they are getting output to and if they are valid. Amazingly handy!

The only problem is that a simulation of one frame takes a few hours... heh.

[alexh]

What simulator are you using? Something as simple as this on say Modelsim should (on an i7) be taking minutes! Are you simulating real blanking delays etc?

[SainT]

I have an old web edition of quartus and I'm using the internal simulator on that. I'll have to update to the latest and give modelsim a go (they deprecated the internal simulator ages ago now). I know that modelsim is at least 1.5x quicker than the older version according to the website, which is something at least.

This is just running a functional simulation as well. I was quite surprised how slow it is...

[Poobah]

Sounds interesting.
How are you handling 50/60 Hz and the various overscan tricks?

[SainT]

Sounds interesting.
How are you handling 50/60 Hz and the various overscan tricks?

I'm currently just doing 50hz at the moment and overscan tricks are fine as they just change when the display enable is active.

The ST actually outputs 2048 cycles per line -- which is 1024 pixels in med res and 512 in low res. Although not all pixels are usable due to horizontal blanking period and just not being visible on screen.

Unfortunately hdmi doesn't have a standard video mode using a 32mhz pixel clock at 50hz, I have to use 720x576p which is a 27mhz pixel clock. This works out well, but means the ST image is actually larger on the screen due to there only being 864 cycles per line.

I am sampling the full 1024 pixels per line, then using the centre 720 pixels to map onto the active pixels of the hdmi output. This gives pixel perfect output.

60hz should be ok, but I've not tried setting up a video mode for it yet. The only difference on a real ST is that you have 2034 cycles per line instead of 2048. I'm hoping my monitor will be happy with this same change in hdmi...

Hi res will also fine! I plan to do a fixer program to enable hi res on the desktop change resolution dialog so you can just switch between any video mode.

I'm making good but slow progress.

[troed]

I am sampling the full 1024 pixels per line, then using the centre 720 pixels to map onto the active pixels of the hdmi output. This gives pixel perfect output.

If I'm reading this right it means you're seeing only tiny borders? That is, any demos or games that rely on fullscreen tricks will have content that's not visible.

(Which was true even on regular TV-sets, but we had some sort of idea of how much most did display)