HDMI Woes

Lamaman1971 · Jan 1st 2022

Hi Folks,

I had some time over the holidays to take a look at a HDMI issue I experienced when I first got my MK3 - and before I begin note that my MK3 works faultlessly with the VGA output.

However, when using HDMI the output consistently blanks screens in a variety of ways:

1. Dell 2410 - Sends Monitor into Standby after a very short time

2. Asus PG279 - No Display

3. Dell S2721QS - Display but flashes on an offer every half second or so.

Not sure where to start looking - I assume that the MK3 should just work with HDMI "out of the box"?

My configuration is as follows:

A1200

TF1230

MK3

Internal GoTek

IDE CF Card

Measuring 4.82v on the AmigaKit Sensor Display.

Any help would be appreciated as my wife would "really" like to reduce the monitor count in the office! . Thanks & Happy New Year,

Mark

nuttie · Jan 1st 2022

Hi,

In case it helps, all of the problems you've listed I've also seen when I've tried to use thinner, not so well shielded HDMI cables in the past. I am not saying that's what your problem is but it might be worth checking the cable to rule it out first if you haven't already. You don't need a super-fancy expensive one, just a decent one that's not super thin or of the flex-ribbon type, as a lot of those are not shielded properly and the signals get messed up as it travels along it. For example, the HDMI cable I'm using at the moment cost about £4-5, is 2m long, and was meant for a raspberry pi. It works fine with the Mk3 at 1080p on my TV, with the output pixel clock running at 148.5MHz.

The display blinking on and off, or not displaying at all could be related to the front/back porch settings or other timings of the output video mode the Mk3 is set to, being slightly out from what the displays expect - What video mode are you running your Mk3 in? Some of my monitors and TVs are terribly picky about resolution and refresh rate settings over HDMI, so yours might be too. If you haven't already, try using the menu option "Settings"->"Re-Read Monitor Display Data..." in the Indivision settings tool, to detect the available screen modes your monitors are advertising when the HDMI cable is plugged in (you might need to have the Amiga connected via the original DB23 analogue video out -> a TV to see what you're doing).

The 1024x768 and 1280x1024 Mk3 presets worked okay for me but caused the screen to get scaled into the middle of my displays and the 1920x1080 60Hz did not work at all for my displays but again that's my displays being picky and not the Indivision's fault.

In case it's useful, these modes work for me...

1920x1080 @ 60Hz
Pixel clock: 148500000
Horizontal Timing:
Visible: 1920

F. Porch: 88

Sync Len: 44

B. Porch: 148

Polarity: Pos

Freq kHz: 67.5000

Vertical Timing:
Visible: 1080

F. Porch: 5

Sync Len: 5

B. Porch: 35

Polarity: Pos

Freq Hz: 60.0000

1920x1080 @ 50Hz

Pixel clock: 148500000

Horizontal Timing:

Visible: 1920

F. Porch: 528

Sync Len: 44

B. Porch: 148

Polarity: Pos

Freq kHz: 56.2500

Vertical Timing:

Visible: 1080

F. Porch: 4

Sync Len: 5

B. Porch: 36

Polarity: Pos

Freq Hz: 50.0000

1280x720 @ 60Hz

Pixel clock: 74250000

Horizontal Timing:

Visible: 1280

F. Porch: 110

Sync Len: 40

B. Porch: 220

Polarity: Pos

Freq kHz: 45.0000

Vertical Timing:

Visible: 720

F. Porch: 5

Sync Len: 5

B. Porch: 20

Polarity: Pos

Freq Hz: 60.0000

1280x720 @ 50Hz
Pixel clock: 74250000

Horizontal Timing:

Visible: 1280

F. Porch: 440

Sync Len: 40

B. Porch: 220

Polarity: Pos

Freq kHz: 37.5000

Vertical Timing:

Visible: 720

F. Porch: 5

Sync Len: 5

B. Porch: 20

Polarity: Pos

Freq Hz: 50.0000

Last thought, (which I should have asked at the top of the post)... have checked you are updated to the latest version of the firmware and tool?

Jens · Jan 3rd 2022

Quote from Lamaman1971

Measuring 4.82v on the AmigaKit Sensor Display.

Not sure how accurate that is, but it's already violating the Commodore spec, which requires the voltage in the computer to not fall below 4.95V on full load. What type of PSU are you using?

Is the shield of the A1200 installed? Is the monitor output PCB directly connected to that shield?

Lamaman1971 · Jan 3rd 2022

Thanks to both Nuttie and Jens.

So I got the indivision HDMI working and stable after some playing around with lower resolution settings in the software. On the U2410 its a nice, clean stable picture running at 1280 x 1024 60hz -> 800 x 600 PAL for standard PAL : Hi-Res Laced. When I get time Ill look to increase the resolution but for right now this is working fine.

Nuttie - your email drove me back to the software and challenged a few assumptions I had made. So thankyou.

Jens : The PSU is a not one of yours - and as far as I can ascertain your view is that all others are inferior? As such, until you get some in stock its irrelevant. As for the measurement, well, on a complex PCB the measurement is only as accurate as the point you take it off - and, for me, the AmigaKit sensor is identical to the measurement taken from the floppy connector - so good enough. Not sure what you are looking for in terms of "monitor output PCB directly connected to the shield? Obviously not because that would be silly and this Amiga was purchased without one. Even if I had one I wouldn't use it - there is far more likelihood of a short than any kind of RF interference. Besides, the symptoms of the HDMI issue I was having were not symptomatic of RF interference - had that been the case all three test monitors would have had similar display issues.

If we have any other U2410 users out there Id be interested to hear how they have it set up.

Cheers

Mark

Jens · Jan 3rd 2022

Quote from Lamaman1971

The PSU is a not one of yours - and as far as I can ascertain your view is that all others are inferior?

Unfortunately, the technical facts don't leave me any other choice. This may look like "bashing" to someone who doesn't take the time to work through the specs, but the nice thing is: The CA-PSU has convinced a lot of people.

Quote from Lamaman1971

As for the measurement, well, on a complex PCB the measurement is only as accurate as the point you take it off - and, for me, the AmigaKit sensor is identical to the measurement taken from the floppy connector - so good enough.

The A1200 is a multi-layer board, and the voltage deviation from point to point within the board is under 0.03V. However, noise can still be troublesome, hence my question about the shield - at least the lower shield should be installed and all screws in place.

Quote from Lamaman1971

there is far more likelihood of a short than any kind of RF interference.

Wow - your expertise in smelling EMI must be so good. So you're saying that shielding is not required, and higher pixel clocks not working on certain monitors have nothing to do with HF on the supply lines. According to that logic, supply voltage does not interfere with the PLLs of the FPGA. Wow. You should write a book and get rich, as generations of electrical engineers have something to learn from you.

Seriously - we should turn to less polemic and more technical methods, otherwise I see no point in attempting to provide support for you.

Lamaman1971 · Jan 3rd 2022

Hi Jens, it wasnt my intention to upset you and there is no need to be sarcastic or defensive. I am simply a customer asking for a little bit of help.

The lower shield is, of course, in place.

You are correct, I cannot smell EMI. However, I hope this is a safe space to disagree with your take on the upper shield - I do not want to loose your support for the MK3 simply because I disagree with you on this point.

I agree the power supply situation could be better and our previous email correspondence support this.

Anyway - since the Amiga is working fine with the MK3, I honestly regret responding at all this morning. Have a nice day.

Jens · Jan 3rd 2022

Quote from Lamaman1971

simply because I disagree with you on this point.

If you do, you probably have some measurements or other facts to back it up. I'm happy to check those, as I have another half a life of learning ahead of me.