Project: HDMI/DVI out for STFM

Progress on our FPGA cores.
User avatar
exxos
Site Admin
Site Admin
Posts: 24262
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: Project: HDMI/DVI out for STFM

Post by exxos »

Can you measure the voltage from the PSU 0v to 0v on the HDMI connector ( or somewhere as far up the board as possible) ?
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
Icky
Site Admin
Site Admin
Posts: 4014
Joined: Sun Sep 03, 2017 10:57 am
Location: UK

Re: Project: HDMI/DVI out for STFM

Post by Icky »

exxos wrote: Thu Dec 06, 2018 12:19 am Can you measure the voltage from the PSU 0v to 0v on the HDMI connector ( or somewhere as far up the board as possible) ?
I did not get to this last night. CPU failed on my PC. Am not doing well with several PSU issues last month and now CPU failure this month.

I should get time to look at this tonight.
User avatar
Smonson
Posts: 714
Joined: Sat Oct 28, 2017 10:21 am
Location: Canberra, Australia
Contact:

Re: Project: HDMI/DVI out for STFM

Post by Smonson »

Sorry to hear about your CPU Icky. That really sucks.

Also I ran my machine on an ATX PSU at 5.06v for over fifteen minutes, but unfortunately didn't experience a single bad read. Ah, well.
User avatar
Smonson
Posts: 714
Joined: Sat Oct 28, 2017 10:21 am
Location: Canberra, Australia
Contact:

Re: Project: HDMI/DVI out for STFM

Post by Smonson »

I measured a differential of around -4 millivolts between the FPGA board to the chassis ground (measured off the big electrolytic near the power supply). Not too bad considering the whole mod draws a lot of current (over 300mA).
czietz
Posts: 556
Joined: Sun Jan 14, 2018 1:02 pm

Re: Project: HDMI/DVI out for STFM

Post by czietz »

I think tuxie's comment was more meant to measure the dynamic ground offset (not the DC offset). I.e. he was saying the same as me in https://www.exxosforum.co.uk/forum/viewt ... 360#p15179.
User avatar
exxos
Site Admin
Site Admin
Posts: 24262
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: Project: HDMI/DVI out for STFM

Post by exxos »

Smonson wrote: Thu Dec 06, 2018 10:00 am I measured a differential of around -4 millivolts between the FPGA board to the chassis ground (measured off the big electrolytic near the power supply). Not too bad considering the whole mod draws a lot of current (over 300mA).
That doesn't sound right.. With a scope across grounds you should see ringing and all sorts of chaos likely going +/- 1V or so.

This is a example of VCC rail.. (images taken a couple years ago)

n2.png
n2.png (2.08 KiB) Viewed 4551 times

and a gnd spike..

n1.png
n1.png (1.53 KiB) Viewed 4551 times

This was across the CPU pretty much, so like 1cm of track. Once it gets to like a foot long trace, welcome to crazy town!

I don't know how immune FPGA are, put some inputs can "latch up" if the voltage is to high or low on a input.
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: 714
Joined: Sat Oct 28, 2017 10:21 am
Location: Canberra, Australia
Contact:

Re: Project: HDMI/DVI out for STFM

Post by Smonson »

Oh, right. That was a DC offset. On the scope I saw occasional noise on the HDMI board ground of up to about +/- 650mV relative to PSU ground. But that shouldn't affect the level shifting buffer direction signal, I think, as it's localised to the mod board only.
User avatar
exxos
Site Admin
Site Admin
Posts: 24262
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: Project: HDMI/DVI out for STFM

Post by exxos »

Smonson wrote: Thu Dec 06, 2018 11:19 am Oh, right. That was a DC offset. On the scope I saw occasional noise on the HDMI board ground of up to about +/- 650mV relative to PSU ground. But that shouldn't affect the level shifting buffer direction signal, I think, as it's localised to the mod board only.
As a mad idea, could you double the length of your ribbon cable on your board and try tests again ? Make sure PSU is at 5V or even 5.2V.
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: 714
Joined: Sat Oct 28, 2017 10:21 am
Location: Canberra, Australia
Contact:

Re: Project: HDMI/DVI out for STFM

Post by Smonson »

Will do! ...soon, but not for a couple of nights, I have my work Christmas party tomorrow.

I can't actually set the voltage - my bench power supply can only supply 1.5A and the ST is just a bit too much for it. So I just have the ATX power supply which is fixed.
User avatar
sandord
Posts: 678
Joined: Mon Aug 13, 2018 10:08 pm
Location: The Netherlands
Contact:

Re: Project: HDMI/DVI out for STFM

Post by sandord »

Smonson wrote: Thu Dec 06, 2018 12:20 pm Will do! ...soon, but not for a couple of nights, I have my work Christmas party tomorrow.
Ah, be sure to bring your ST then and run this:

Post Reply

Return to “FPGA DEVELOPMENT”