Project: HDMI/DVI out for STFM

Progress on our FPGA cores.
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: Project: HDMI/DVI out for STFM

Post by exxos »

Smonson wrote: Fri Oct 26, 2018 10:35 am Do you know of a schmitt buffer that can also do 3.3 -> 5v level translation though? That's the thing.
Any buffer will do that pretty much... The buffers are use on my STE booster are basically being driven with about 3V input... Because the rise and fall times of the GAL are pretty slow so it never reaches the full 5V...

The buffer chip runs on 5V.. And outputs a nice 5V to the CPU. As it is a schmitt buffer, its hysteresis extremely good and it filters out any tiny noise or glitches in the signals.

I did actually try regular buffers and they were frankly terrible in comparison.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
Smonson
Posts: 708
Joined: Sat Oct 28, 2017 10:21 am
Location: Canberra, Australia
Contact:

Re: Project: HDMI/DVI out for STFM

Post by Smonson »

This is a comparison between the original (regular logic) buffer, and the clock fanout buffer at 16MHz. It's clear that the new one is a more forceful driver. The clock on the 68k pin is quite rounded still, I think 100 ohms in series is a bit on the high side to get any benefit from the squarer signal coming out of the buffer. The signal going into the buffer is also pretty sine-y after passing through the series resistor and the ribbon cable, I can experiment more with lower resistor values at some point.
old-clock.png
old-clock.png (6.3 KiB) Viewed 4054 times
new-clock.png
new-clock.png (5.52 KiB) Viewed 4054 times
Speaking of Schmitt triggers, do you mean something like SN74LVC1G17? I'll add a few to my next mouser order and can test one out and see how it goes.
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: Project: HDMI/DVI out for STFM

Post by exxos »

Smonson wrote: Fri Oct 26, 2018 2:23 pm This is a comparison between the original (regular logic) buffer, and the clock fanout buffer at 16MHz. It's clear that the new one is a more forceful driver. The clock on the 68k pin is quite rounded still, I think 100 ohms in series is a bit on the high side to get any benefit from the squarer signal coming out of the buffer. The signal going into the buffer is also pretty sine-y after passing through the series resistor and the ribbon cable, I can experiment more with lower resistor values at some point.
The resistor value just be there to stop the ringing.. You're not far off with your bottom image anyway.. Somewhere around 33R is normally a good value.
Smonson wrote: Fri Oct 26, 2018 2:23 pm Speaking of Schmitt triggers, do you mean something like SN74LVC1G17? I'll add a few to my next mouser order and can test one out and see how it goes.
Yeah I think that is the one I am using on my booster....

It gets driven by something like a 1.5V - 3.5V sinewave on its input (from my GAL) and it cleans it up to a really nice square wave at 40MHz to the 68K CPU.

I normally take scope readings of things like this, but I cannot see it in my thread :(
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
Smonson
Posts: 708
Joined: Sat Oct 28, 2017 10:21 am
Location: Canberra, Australia
Contact:

Re: Project: HDMI/DVI out for STFM

Post by Smonson »

I'd like to take an informal poll, if anyone who has an opinion would care to respond -

Which video connector would you prefer to see on this mod: HDMI or DVI?

HDMI connectors are cheaper and use less board space (and need a smaller hole in the back of the ST). But the DVI connector seems a lot more physically sturdy.

Both types of connector carry the same signals and both are compatible with DVI and HDMI monitors and TVs.

In either case, audio would not be transmitted through the connector - just to be clear.
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: Project: HDMI/DVI out for STFM

Post by exxos »

Didn't you say one connector was under licencing or something a while back ?
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
Smonson
Posts: 708
Joined: Sat Oct 28, 2017 10:21 am
Location: Canberra, Australia
Contact:

Re: Project: HDMI/DVI out for STFM

Post by Smonson »

Yes but I don't think anyone is really going to care, since I'm not a company.

...Right?
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: Project: HDMI/DVI out for STFM

Post by exxos »

Smonson wrote: Tue Oct 30, 2018 10:57 am Yes but I don't think anyone is really going to care, since I'm not a company.
Yeah.. true.. only the flack I get off companies for doing nothing is unreal :roll: There was a company to verify the quality of some goods I use.. I mentioned that on my website.. then they sent me a letter last week saying I didn't have permission to do that unless I paid them.. no thanks.. Bit pointless having a company to verify products then not being able to mention them! Just greedy companies as usual..


Anyway..

I see the advantages of the larger connector with it being more robust.. But in case of connections on monitors, I'm not even sure what my it is used a larger connector any more...? My cheap TV uses a smaller HDMI connector.. So I end up doing this..

IMG_3399.JPG
IMG_3399.JPG (35.68 KiB) Viewed 4002 times

So I think having the smaller connector probably more of a advantage.. Of course it may not be as strong, but we can look into options or different manufacturers of connectors to see which is the strongest one..

Of course the workaround for licensing issues, will be to not supply the connector with the board.. I don't think it is a problem to buy and sell the connectors themselves... But using that connector on a actual product would be a licensing infringement.. It may be worth looking at their licensing terms, see if there is a workaround like low-volume or prototypes can be used without licensing...

But yes, nobody should really care, but I thought that about my web shop when someone reported me got me shut down.. Only takes one person looking to cause trouble.. And I have had many over the years :(
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
rpineau
Posts: 534
Joined: Thu Aug 17, 2017 6:08 pm
Location: USA
Contact:

Re: Project: HDMI/DVI out for STFM

Post by rpineau »

I'll also go HDMI for convenience.
Working ones : MegaSTE (68020) / TT030 / Falcon with AB040 & Eclipse / 1040STF
Need testing : Falcon with CT2
User avatar
IngoQ
Site Admin
Site Admin
Posts: 1066
Joined: Tue Aug 22, 2017 8:38 am
Location: Germany

Re: Project: HDMI/DVI out for STFM

Post by IngoQ »

I'd say stick with the DVI, just to make sure. If size is a matter you can always go with MiniDVI or MicroDVI. In addition, DVI-I would allow you to output both analog and digital RGB on the same connector.

DVI to HDMI Adaptors are cheap as chips, and could even be included, in my mind not worth the risk of a costly cease and desist letter.
Ingo :geek:

| Atari 1040STE@32MHz | Amiga 1200 (ACA1220) | Atari 800XL (U1MB, SIDE2) | Atari 130XL (Sophia DVI) | C64 (1541 Ultimate II, Rev3 RFMod Replacement) | TI 99/4A (F18A, 32k, FlashROM 99) | Sinclair ZX Spectrum 128 (Stereo, DivMMC) | Amstrad CPC664 (512k, M4 Wifi) | ... |
User avatar
PaulJ
Posts: 1568
Joined: Sun Apr 08, 2018 1:14 am
Location: USA

Re: Project: HDMI/DVI out for STFM

Post by PaulJ »

Smonson wrote: Tue Oct 30, 2018 10:14 am I'd like to take an informal poll, if anyone who has an opinion would care to respond -

Which video connector would you prefer to see on this mod: HDMI or DVI?

HDMI connectors are cheaper and use less board space (and need a smaller hole in the back of the ST). But the DVI connector seems a lot more physically sturdy.

Both types of connector carry the same signals and both are compatible with DVI and HDMI monitors and TVs.

In either case, audio would not be transmitted through the connector - just to be clear.
Personally I'd like to see an HDMI connector. Most things today have an HDMI input and if not there are plenty of HDMI to DVI cables available.
Post Reply

Return to “FPGA DEVELOPMENT”