Project: HDMI/DVI out for STFM

General discussions or ideas about hardware.
troed
Posts: 333
Joined: Mon Aug 21, 2017 10:27 pm

Re: Project: HDMI/DVI out for STFM

Post by troed » Sun Sep 09, 2018 11:50 pm

exxos wrote:
Sun Sep 09, 2018 11:43 pm
Very odd...

What board exactly are you using ? I can try and find same board here to try out..
C070243 REV.I (520STM)

Even if there's something different with my FPGA prototype compared to yours I still don't understand how ...

User avatar
Smonson
Posts: 145
Joined: Sat Oct 28, 2017 10:21 am

Re: Project: HDMI/DVI out for STFM

Post by Smonson » Mon Sep 10, 2018 3:35 am

To eliminate the possibility of power supply issues, could you try running the machine with the stock shifter installed, but with the FPGA board connected to just +5, ground, and vysnc? If possible, from somewhere connected close to the shifter socket. Then it should run through video generation just by itself and possibly introduce power supply or ground noise.

User avatar
exxos
Site Admin
Posts: 3461
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: Project: HDMI/DVI out for STFM

Post by exxos » Mon Sep 10, 2018 10:12 am

Smonson wrote:
Mon Sep 10, 2018 3:35 am
To eliminate the possibility of power supply issues, could you try running the machine with the stock shifter installed, but with the FPGA board connected to just +5, ground, and vysnc? If possible, from somewhere connected close to the shifter socket. Then it should run through video generation just by itself and possibly introduce power supply or ground noise.
That is a good idea.

In fact, both shifter and FPGA could actually be soldered on top of each other ? If Troed solders a socket on top of the shifter, plugs the shifter into the MB, then the FPGA into the socket.. then he can run both at the same time ? If both outputs work, that would be interesting..

If troed has a diagnostic cart, might be worth running with that to see if any bad bits in RAM test show up before the reset.. I'm thinking bus loading issues when the FPGA is installed...

Might also be worth running VSYNC via a 100R resistor as well...
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

User avatar
Smonson
Posts: 145
Joined: Sat Oct 28, 2017 10:21 am

Re: Project: HDMI/DVI out for STFM

Post by Smonson » Mon Sep 10, 2018 10:27 am

Smonson wrote:
Mon Sep 10, 2018 3:35 am
In fact, both shifter and FPGA could actually be soldered on top of each other
Hmm, the problem with that is they'll both try to drive the outputs (data bus, 16mhz clock). Also I have tied the unused pins to ground on the shifter socket adapter PCB, so those would short out some of the shifter's pins, such as the RGB lines, if they're connected.

troed
Posts: 333
Joined: Mon Aug 21, 2017 10:27 pm

Re: Project: HDMI/DVI out for STFM

Post by troed » Mon Sep 10, 2018 10:28 am

exxos wrote:
Mon Sep 10, 2018 10:12 am
If troed has a diagnostic cart, might be worth running with that to see if any bad bits in RAM test show up before the reset.. I'm thinking bus loading issues when the FPGA is installed...

Might also be worth running VSYNC via a 100R resistor as well...
Yeah I have. Although if that was the problem I cannot see how it would always be a reset - should be bombs and corruption. VSYNC issues would also just cause the display to flicker/blank out - not reset.

I only checked with the LA that VCC didn't short out before RESET - I'll do the dual load as well as scope it also.

(The 520 runs off a picoPSU and the doubleST a recapped regular Atari PSU running at 5.11V - so they're not similar in that aspect)

User avatar
exxos
Site Admin
Posts: 3461
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: Project: HDMI/DVI out for STFM

Post by exxos » Mon Sep 10, 2018 10:34 am

troed wrote:
Mon Sep 10, 2018 10:28 am
Yeah I have. Although if that was the problem I cannot see how it would always be a reset - should be bombs and corruption. VSYNC issues would also just cause the display to flicker/blank out - not reset.
Yeah it should yes, but knowing how screwy these machines are, whos to say the extra load on VSYNC isn't causing ringing on the GLUE, causing GND bounce or something and causing the GLUE to malfunction causing the reset.

That's the kinda of screwy problems I am fighting all the time with these machines, also why its long term easier just to create a new motherboard ;)

Its easy things to try.. may not help, but never know, and it rules some things out :)
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

User avatar
Smonson
Posts: 145
Joined: Sat Oct 28, 2017 10:21 am

Re: Project: HDMI/DVI out for STFM

Post by Smonson » Mon Sep 10, 2018 10:50 am

exxos wrote:
Mon Sep 10, 2018 10:34 am
but knowing how screwy these machines are, whos to say the extra load on VSYNC isn't causing ringing on the GLUE
Yeah, I agree. It could also be bad grounding since my entire board is powered and grounded through a single pin each in an IC socket, which is probably not the best if it's going to draw hundreds of milliamps of current.

The fact that my machine is incredibly stable makes me think that whatever the problem is, it must be near some threshold where I'm just under it and you guys are just over it. It feels like an analogue problem.

User avatar
exxos
Site Admin
Posts: 3461
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: Project: HDMI/DVI out for STFM

Post by exxos » Mon Sep 10, 2018 10:56 am

Smonson wrote:
Mon Sep 10, 2018 10:50 am
Yeah, I agree. It could also be bad grounding since my entire board is powered and grounded through a single pin each in an IC socket, which is probably not the best if it's going to draw hundreds of milliamps of current.

The fact that my machine is incredibly stable makes me think that whatever the problem is, it must be near some threshold where I'm just under it and you guys are just over it. It feels like an analogue problem.
Yeah, I see that type of issue all the time. Like with my boosters, can work perfect for days on one machine, then identical other MB and nothing but trouble :( It could be literally anything..

I mean if the ribbon cable is half the length that could make or break something for example. Running gnd through a thin cable isn't likely helping issues.. Might be something else Troed could try, is making the cable as short as possible..
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

troed
Posts: 333
Joined: Mon Aug 21, 2017 10:27 pm

Re: Project: HDMI/DVI out for STFM

Post by troed » Mon Sep 10, 2018 1:07 pm

Yeah analogue is where I'm lacking all knowledge. Adding a fat ground wire is an immediate thing I can check of course.

Ringing backwards on VSYNC causing GLUE to trip up is actually the best explanation so far as to what can happen that causes _resets_ always ;)

alienkidmj12
Posts: 20
Joined: Tue Aug 22, 2017 1:39 pm

Re: Project: HDMI/DVI out for STFM

Post by alienkidmj12 » Fri Sep 14, 2018 9:09 pm

this is awesome stuff :) keep up the good work, id buy one for each ste/stfm :)

Post Reply