Extremely noisy image issue on 7" TFT (two of them!)

[maxj]

Hello,

I recently purchased two of this item: https://www.adafruit.com/product/1933

I have previously used https://www.adafruit.com/product/1928, which I have had no issues with.

The images I'm getting on the display when using HDMI are super noisy and colorful. I've tried the following debugging steps:

- Using a different HDMI cable
- Using a different power supply
- Trying both driver boards/LCDs
- Seating the display connector as deeply/solidly as I can
- Driving HDMI from a windows PC instead of my linux laptop

Interestingly, changing the brightness setting on the driver by even 1 completely changes the color of the image.

Here is a video: https://youtu.be/ujvnwQ_1Fso

Also worth noting is that the UI elements for the driver board (used to change color settings etc.) do not show up with any noise. So I think the link between the driver board and the display is OK.

I am very confused.

Thanks for your help!

[mikeysklar]

Hello maxj,

On your linux machine did you customize your config.txt?

https://learn.adafruit.com/hdmi-ubergui ... 0x480-hdmi

Code: Select all

# uncomment if hdmi display is not detected and composite is being output
hdmi_force_hotplug=1
 
# uncomment to force a specific HDMI mode (here we are forcing 800x480!)
hdmi_group=2
hdmi_mode=1
hdmi_mode=87
hdmi_cvt 800 480 60 6 0 0 0
 

Also there are some details about the driver board you might want to review. Including setting the max usb current in the config.txt

https://learn.adafruit.com/hdmi-ubergui ... iver-board

max_usb_current=1

[maxj]

Hello maxj,

On your linux machine did you customize your config.txt?

https://learn.adafruit.com/hdmi-ubergui ... 0x480-hdmi

Hi,

I went ahead and tried that exact configuration, and I'm still experiencing this issue. See the second image for my exact setup:

https://imgur.com/a/ohjfp8F

The first image shows the noise on the background image but not the driver board's UI. You can see the noise in the menu bar.

The noise flickers at a pretty constant rate of 2Hz or so. Also, I just tried powering the display from the raspberry pi, and the results are the same.

[mikeysklar]

There is a comment in the guide for the rtd2660 driver about the USB cable needing to be good enough. I just want to make sure you added the max_usb_current=1 and are driving your Pi from a 2A or higher source.

Code: Select all

max_usb_current=1

If you're getting wierd reboots, its likely the power supply and/or power USB cable is not good enough. A powered hub will also solve this problem

[maxj]

For reference, here is a picture of me driving a https://www.adafruit.com/product/1928 using the exact same setup as in the above picture (taken moments later):

https://imgur.com/a/rn8YpZ0

Please excuse the fact that I have ripped the backlight out -- just notice that the colors make sense and there's no noticeable noise in the image :)

[maxj]

There is a comment in the guide for the rtd2660 driver about the USB cable needing to be good enough. I just want to make sure you added the max_usb_current=1 and are driving your Pi from a 2A or higher source.

Code: Select all

max_usb_current=1

I just went ahead and powered the display driver from my external power supply at 5v. It is drawing 521mA and is still displaying the noise.

[maxj]

Here is a better video of the noise:

https://youtu.be/jmTBZuBKVt0

[maxj]

I dumped the firmware from the display driver, attached. Are you able to confirm that this is the expected firmware?

[maxj]

lol, I fixed it!

https://imgur.com/a/90zryG9

I flashed a firmware for a similar driver board, the PCB800099, and for a similar LCD, the AT080TN92. I found the firmware on this random github repo: https://github.com/riftbit/RTD2660_PCB8 ... ey-IR2.bin

The only side effect is my driver board thinks it has a VGA port :)

So, the problem is solved for me, but I'm pretty sure I was shipped two driver boards with incorrect firmware!

[mikeysklar]

Hi maxj,

Nice job uploading a custom github firmware onto your TFT. I'll be on the lookout for for similar 7" TFT issues. What setup did you use to download the firmware from the display and upload the github code?

[maxj]

What setup did you use to download the firmware from the display and upload the github code?

I used a Raspberry Pi 4 and this project: https://github.com/klirichek/RTD-2660-Programmer. I just hooked up the i2c pins on the Raspberry Pi to the labeled i2c pins on the driver, enabled the i2c peripheral with `raspi-config`, and ran the python script in the repo.

I had to modify `pyprog.py` slightly in two ways:

- It didn't know about the flash chips my driver was using, so I just added a dummy entry to the `FlashDevices` list to make it work (just a dummy entry with the jedec ID that it scanned, I don't remember what it was unfortunately. I think the size was 512k.).
- The `SetupChipCommands` check seemed like it was broken, so I just bypassed it (I made it so that it always ran the extra commands, but in retrospect it would have been safer to just delete the call to that function entirely... I bet it would've still worked fine).

[mikeysklar]

Very nice. Thank you for sharing your technique. I'm sure this will come in handy for others.