MiSTer FPGA Forum

Hello,
I have been trying to diagnose a rather strange issue i have started to have with my mister setup, I use the mister in a LAI arcade cabinet running directly off the analogue board VGA into the CRT chassis, All works well apart from when the mister boots and im presented with the static background, the pattern of the white noise seems to flicker between two different styles. Its a bit hard to explain, so I have uploaded a short video of the issue here: https://youtu.be/q-xHx-nBlHg

i have been doing a fair bit of digging through these forums to find out if anyone has experienced anything similar but with no luck.

Recently i pulled the mister out of my arcade cab and in an attempt to find out what is causing the issues i have done the following,
Rebuilt the mister software on a new SD card using the recent mrfusion install, then updated the system using the update script.
booted the DE10 board on its own - i.e eliminated the issue being to do with the analogue I/0 board, USB expansion board and the 128mb SDRAM board.
The strange flickering is present on both the VGA and HDMI outputs.

So my question is, Have i somehow damaged the DE10? i cant think of any other way to try and isolate the fault.
I am at a loss as to what to try next, Apart from the flickering the mister seems to work fine, its just distracting when im running it on the arcade CRT.

Any ideas on whats possibly causing it?

Cheers,
Allan

I think i have found out whats causing it, I have just downloaded the previous version of the menu core https://github.com/MiSTer-devel/Menu_Mi ... r/releases
When i run Release 20210315 the issue clears.
is this possibly a issue in the current release of menu.rbf?

Some information from Sorgelig about how the white noise on the menu screen is generated.

Sorgelig Wed Nov 06, 2019 7:37 pm
Noise screen comes from true noise produced by FPGA. It's NOT pseudo random generator using some calculations.
So it depends on temperature of chip and initial state.

Sorgelig Wed Nov 06, 2019 11:20 pm
Basically it's cyclic connection of several CELLs of FPGA without any clock. So they start to transfer the data by circle at maximum speed they can including failed transfers. This produces the chaos in the chain depending on temperature and some other factors.

At some point i've tried to abandon this random generator in favour of traditional "software" generation, but result wasn't as good as true HW random generator.

Source: TV Static Background Changes at Random?

It's an interesting read, but I do think Agentbarry might be onto something here. I've been thinking about this for quite some time - pehaps indeed since that last 20210315 menu version - but haven't asked about it because I wasn't quite sure it's an actual thing, and also it's of course not that important.

But now looking at the pattern generated on that older rbf it is indeed much different from the new one. Much more tranquil and uniform, but most importantly lacking the spasmodic jerkiness of the new one. That's the biggest issue - no the pattern itself (which is more coarse in the new one), but the fact that in the new one the it kinda flickers/jerks/switches quite often (yes, hard to find the right word for it, or even see that well in the video). Not sure if it manifests itself on HDMI, or only on CRTs, but it's definitely not as pleasant as the old one.

Like I said, I do realize this is about as unimportant as things get but, hey, this is MiSTer, home of the obsessives Perhaps worth an explanation or fix, if possible.

A way around the problem is not to display the static at all. The F1 key will cycle between the static and some existing, static background images. You can add your own, either as menu.png, or by creating a 'wallpapers' directory and populating that.

The center of your image is rock solid, so I'd just avoid the problem entirely.

Hi all,
Cheers for the discussion around this, it is nice to know that its not necessarily something I have done to the de10, I do use the static background wallpapers when I take the Mister out of the arcade machine and run it via HDMI, but once I have it back running on my arcade CRT I'm using the direct 15khz output from the VGA port. I have found it really hard to get the CRT to setup properly with VGA scaler enabled.
Plus the static screen is great I did not realize it was truly random and based off environmental factors, thanks for the link to the discussion around that.
as @akeley said, I totally understand that this is very low priority, initially I wasn't sure if something was failing in my hardware was all as I have had a few issues the the CRT chassis.