PI-TOP screen flickers

pi-top [4]
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#20

Thanks for any help you can give! The last update I got was they were sending the request over to somebody who would send the cable out and they would give me an update. I haven’t heard anything back and it’s been a while. I sent an update request about a week ago, and haven’t heard anything.

The cable I built isn’t production ready by any means, it was simply more a tool for troubleshooting my display issues, since I have been waiting for the cable to arrive. There is no shielding, or any type of real design. I believe you posted a pinout in another thread. I used that as a start (I think there may have been a typo or 2 on it, but nothing too serious). I then mapped out the video display adapter, to figure out how the HDMI and USB signals were split off in the Pi-Top cable. It’s a really cool cable you guys designed!

Slightly off-topic sidebar Speaking of that, I am not sure if you’re aware but the build quality of (at least my) video adapter board is super poor. A couple of the wires were barely being held on, part of the green plastic piece that holds the wires in place was melted (although, I will fully admit I have since added to that!) there were cold solder joints all throughout, and the one side of the board is rough copper, bad enough that you can cut yourself if not careful. I have since added another (currently non-working) cable to that board to futher my troubleshooting and tinkering, but before I did that I reflowed all the points on the adapter board and did see an increase in video quality.

I then used these nifty breakout boards https://www.amazon.com/gp/product/B08TH8S1J7/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1 to build the prototype cable. Unlike most other male USB-C connectors I found, this one breaks out all of the pins, so I was able to copy the custom cable. It works enough to reproduce the jittering the original cable has, but is also finicky, so another original cable would be hugely helpful in troubleshooting.

@Supernovali I will PM you my address! Thanks! The jittering only occurs when using the green cable/my cable directly. It occurs regardless of OS. I actually am using Ubuntu Mate on it now and see the same jittering that PiTop OS has. Although, the thought has occured to me that it could be a softeware/driver glitch. I have seen similar jittering on touchscreen laptops that has been fixed with a driver update.

I have never been able to get the Pi-Top to work with the video display adapter at all actually using the Pi-Top’s HDMI port. I either get a black screen, or heavy artifacting, similiar to a video card failure in a PC. Before my tinkering, the display adapter did work perfectly with other (non Pi-Top) devices connected to the Pi-Top display (no jittering in that case.) Also, I can connect the Pi-Top to another display using its HDMI port and that works perfectly.

My display adapter is no longer working at all, but it could be due to my tinkering. I see nothing wrong when I check everything with a multimeter though, so I am a bit stumped. I may undo all my custom work and see where I am at. However, since the Pi-Top never worked with the adapter even before my alterations, perhaps there is some underlying issue that I am not accounting for.

#21

By chance, does your jittering look like this? I got this the other day and unplugging and plugging it back it worked… but with all of the troubleshooting you’ve done, I dont think that will fix it.

20210301_230942

My adapter just needs some testing to make sure it works too. I’ll be designing a snap on case for it too to 3d print but I’m not quite to that point yet. I do know though that those breakout boards usually cant handle the full 1080@60 fps. The signal to transmit is 3GHz so it requires some careful design considerations and maths to get it figured out.

If you used another display though and it worked, that makes me suspect that it’s the screen. Have you talked to @duwudi about that as well? I know they’re pretty bush but he might have some additional insight as well.

And yeah, that was posted by @duwudi as well in the other post and I did find that typo and had to verify it with him. In that schematic that was sent, pin A11 is labeled as TMDS_D1- and should be TDMS_D0-

I have to get going but if that caused confusion, try adjusting your breakout accordingly :slight_smile:

I’ll be on in about an hour and see if I missed anything

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#22

An update regarding the display adapter. I plugged it into my laptop to see if I can get a better idea of what is happening. USB is working perfectly. I have bluetooth off on my laptop, and the Pi-Top keyboard and mouse work great. I also have some touchscreen capability. I can’t control the mouse with the touchscreen, but it is being registered (touching the screen stops the screensaver, or changes the active window.) It also can scroll webpages on Firefox. However, the screen doesn’t display at all. I have tried using both HDMI and HDMI to DP mini. The laptop DOES see the second screen, and unplugging the green cable from the display, or unplugging the USB-C power on the adapter causes Windows to disconnect the second display. I used another display I had to make sure it wasn’t Windows being Windows and that display came right up, with no configuration changes needed.

I have a second cable I built attached to the display adapter to rule out the green cable as being the issue, and it does the same exact thing. I have confirmed continuity on both cables, and all pins on the adpater board, specifically the HDMI port and everything is fine. Could all my issues be due to the logic that is on the hot plug detect pin?

#23

The jittering I normally get looks exactly like the video posted by @TonyZ in the first post. It looks more like the touchscreen isn’t calibrated. The whole screen bounces up and down uniformly. There normally isn’t any artifacting, however I have seen that sometimes when the plug isn’t in all the way, or sometimes the cable needs to be wiggled.

Yes, that was the typo. I assumed it was a typo, and connected the cable the correct way. Plus, I checked continuity on the original green cable and the adapter and confirmed both were wired the same way.

#24

I should also note that wiggling the cable, plugging it in and out doesn’t change the jittering. The jitter doesn’t always happen, I have had sessions of up to an hour without jitter. But, most times it is present. It ranges from barely noticable, to completely unusable.

#25

I have that exact issue when using the pi-top using the hdmi out with the display adapter and posted about it here

https://forum.pi-top.com/t/android-tv-on-pi-top-4/343

I still need to contact support about it

#26

Ok ok, I have an idea. Can you open /boot/config.txt, find and comment the line that talks something about signal??? Let me boot up my pi and find the exact line and I’ll get back to you.

Sorry it took a minute, work got crazy

#27

Ok, do

sudo nano /boot/config.txt

and find the line that says

#hdmi_config_boost=4

Uncomment it, save, then reboot and see what happens. If it doesn’t work right away, try increasing the values up to 11 and let me know what happens. Use the lowest number that gets you up and going. :slight_smile:

Also, make sure you have another monitor handy to use in case it gets worse or if you make a mistake.

1 Like
#28

@cavedude nice work on the custom cable, those USB-C breakout boards are tasty! :+1:

I’m going to ask support to send you an entirely new FHD display and display cable - if you could get the display, display adapter and display cable returned to us for debugging that would be excellent. It doesn’t matter than you’ve tinkered with it, it seems the problem has always been there so we’ll be able to figure out the root cause if we have the entire system in our hands.

2 Likes
#29

I completely messed up above too. :man_facepalming:t2: I meant to say the bandwidth is over 3 Gbps haha. As in bits per second. The actual clock rate is 600 MHz I think?

#30

I am giving that a go now, and I’ll let you know the results. I always ssh in, so mistakes are no biggy :slight_smile:

@duwudi I will revert my changes to the adapter and send all 3 your way! I assume I’ll be getting an email from support to start the process?

#31

I made the changes and didn’t see any difference in the flickering. I actually started at 0 and went to 11 (like our amps!)

I did a quick search, and found on https://www.raspberrypi.org/documentation/configuration/config-txt/video.md that hdmi_config_boost is ignored on Pi4. However, I am going through these other options now, and am seeing if any of them changes the flickering at all!

#32

Ok, darn. Was worth a shot I guess. When you say you’re SSH in to it, do you mean you are using another device besides the pi-top to access it? Or just SSH with the issues with the screen?

Yeah, if it doesn’t work with the adapter on either of the raspberry pi’s mini-hdmi connectors and it doesn’t work in the pi-top with the display adapter cable, but it works with other displays, I’d say it it points to a display issue :confused: It’s not 100% but is is up there in the probabilities.

#33

@cavedude yeah I’ve told them to get in touch to get things arranged! Might be worth sending an email in your reply and referencing this forum post though since I’m not sure if your forum email matches your email in the support system

#34

I just checked and confirmed the email address I have in these forums match my Kickstarter account, so hopefully they will be able to track it properly.

I was going to reference this thread when they email me. If they don’t email me within a few days, should I open a ticket?

#35

Yeah, I SSH over the network to a bash prompt bypassing any display issues :slight_smile:

1 Like
#36

Kk, hey, there is another display issue that popped up. Maybe check it out and see if you can follow along to see if you have any of the same results when your display is attatched. I’ll send a link to the thread in a second.

1 Like
#37

Thanks! I already saw that thread and am following it. I definately think in my case, I just have a bad display. It’s hit or miss if it wants to work at all now, so hopefully, support can get me sorted with a new display!

@duwudi I still haven’t heard from support. Should I contact them?

#38

I have a few changes I need to make before I can send out a prototype. I need to make it’s construction more reliable. Eta is another couple of weeks :confused:

#39

Yes, please send an email to support@pi-top.com