Corrupt display on VIM

Technical Support
1

From time to time, the HDMI display gets disturbed, but not always in the same way. Most of the time, the pattern is a blinking pinkish display with pixel noise, but other times it is only pixel noise (swarm of white dots), as if the HDMI signal were disturbed or as if the EDID were misinterpreted. This lasts a few minutes, then everything goes back to normal. This is random, but it seems to mostly occur when the board is cold.

Issue observed with:
1080p60
4K60 HDR
VIM_Nougat_170901.7z
buildroot_openlinux_kernel_4.9_wayland_20170814.tar.gz (mesongxl_p212_32)
several VIM boards
Panasonic TX-40DX700F

Since this occurs for 1080p60, I am certain this is not caused by the HDMI cable. I don’t know if this is caused by the VIM or by the TV, possibly not supporting some EMC stress. Has anyone already observed this?

2

Hi, Ben:
Have you tried with another HDMI output device with the same HDMI cable & TV monitor?

And how many VIM boards you tested? I’m not sure whether HDMI compatiable issue for some monitors, but Amlogic SoCs should be good compatiable for this, is it possiable for you to take a simple video include the VIM board, HDMI cable, Monitor, Adapter and the issues, so our team and I can better understand the issues better.

I will keep follow up the issues, kindly keep update.

Thanks!

3

Hi @Gouwa,

Yes, and it seems to work, but the issue occurs randomly only about 2 or 3 times a week during a few minutes, so it’s hard to know for sure whether or not a given configuration has this issue because a very long test time is required.

I have observed this issue with at least 3 boards.

I will try, but the issue is rare and it lasts only a few minutes, so it may take a while before I can shoot a video.

Thanks!

4

Hi @Gouwa,

You can see the issue in this video (available only 1 week for download):
https://we.tl/veCKW1MbRT

In this video, the ExoPlayer demo application is displaying a paused video, so the image is supposed to be still. However, it blinks between the normal image, green, and black, as if the HDMI signal were periodically lost then recovered. And when the normal image is displayed, there are many whitish dots of different sizes blinking over it (visible from time to time between 0:00:04 and 0:00:06 in the video; much easier to discern on the screen with your eyes than in this video), as if the HDMI signal were disturbed.

The issue recorded in this video started randomly and lasted a few tens of minutes. Displaying something else or switching to another application had no effect on the issue.

Video context:

  • FW: VIM_Nougat_V171028.7z
  • TV: Panasonic TX-40DX700F
  • HDMI: 4Kp60 HDR
  • things connected to the VIM: Khadas power supply on USB Type-C, TV on HDMI, Ethernet, USB flash drive
5

Hi, BenTh.WS:
Does your Sony monitor support MHL(no full HDMI Standard)? And you connected to the MHL port?

I saw similar issue on Sony monitor before, change to HDMI port got the issue resolved. Kindly confirm again!

Thanks!

6

Hi @Gouwa,

It’s a Sony video being played on a Panasonic monitor. This monitor only supports standard HDMI, not MHL.

7

Sorry for the late response.

Yep, I double check the video you posted, I think we need move forward by:

  • Provide us the video to us (or all videos have same issue)
  • Tell us the ROM version you installed
  • Tell us the APP you were playing the issue video.

We can test and confirm here. In additional, do you know how to catch the printing log? A printing log when you play the video will be helpful.

Thanks!

8

Hi @Gouwa,

It was this video:

But it happens with all videos, and even when not playing a video and doing anything else on the VIM. It may even happen when the VIM is idle, only showing the wallpaper.

VIM_Nougat_V171028.7z

This video was played by the ExoPlayer demo:

This app was launched with this intent from an adb shell:

am start -a com.google.android.exoplayer.demo.action.VIEW -d file:///storage/<path-to-the-video>

I can send you a logcat, and also a serial log.

Thanks!

9

I checked the comment you posted before: you’ve tested 3 more VIM board both with same issues, right?

If this issues happens on all videos and all ROMs, and 3+ boards, this might be following:

  • The HDMI resolutions you setup? Can you try with another output resolution?
  • HDMI Cable, can you kindly try with another HDMI cable?
  • DC Adapter: can you tell me the specs and model you were using?
  • HDMI compatible with specified HDMI monitors, if you have another HDMI monitor, also kindly do a test

I might ask too much questions :wink:

Thanks!

10

Correct.

Currently using 4Kp60 HDR. Will do.

Will do.

It’s the AC/DC adapter sold with the VIM:

  • model: JHD-AP012E-050200AB
  • input: 100-240 V AC, 50/60 Hz, 0.35 A
  • output: 5 V, 2 A

I have also already observed this issue with another power supply.

Will do.

11

One more testing:
Change the HDMI output setup and test with current monitor.

Thanks!

12

Hi @Gouwa,

We got several VIM1s experiencing this issue in the last batch that we purchased. So it happens with several VIMs, but not all. For the affected VIMs, it happens with many HDMI cables and monitors.

Slightly moving the HDMI plug inside the receptacle makes the issue appear or disappear. Therefore, it looks more like an HDMI connector issue. There is sometimes too much mechanical play, so the electrical contacts may become loose by barely touching or moving the cable, which corrupts the HDMI signals.

13

How many VIM1 units you found with this issue so for? If necssary, is it possiable for you to ship one of these to us for test and confirmation?

Thanks!

14

So far, we have 3 VIMs having this issue (corrupt display) quite often, and 3 other VIMs, which may cause a black display if we really insist.

We will ship some of these boards to you for analysis.

Thanks.

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