Issues with two panels and a Teensy 4.1

Hello friends! I am having a bit of trouble getting two panels working together with a Teensy. They are 2 32x64 panels that will be arranged as a 64x64 square. I’m not picky about the stacking arrangement because the length of my ribbon cable allows me to rotate a panel if I need to.

Behavior is as expected when using either panel alone but when I try to daisy chain them together, there are issues:
1) the panel directly connected to the Teensy is missing every other row
2) the daisy chained panel is showing random bars of color


  • Teensy 4.1
  • SmartLED Shield V5
  • 2x LED matrices: P4-2020-32*64-16S-S2-RMG (standard 32x64 HUB75 panels)
  • 5V supply with 10A, split into each panel

Two panels broken:
(Feature Demo)

What I’ve tried:

  • Every PanelType listed in the .h file
  • All the different matrix and layer options
  • Adjusting the width and height to be 64, and 64
  • Adjusting refresh rate and dma buffer rows
  • Connecting the ribbon cable to the output port of the second panel (just in case)

What I’m hoping to accomplish for now is just to run the FeatureDemo on a 64x64 square using my two panels. Any ideas? I’m happy to provide more info or post more pics. Thanks!

Can you take a picture of your wiring on the back? Chaining a panel shouldn’t change anything on the first panel so this seems like a hardware issue

There is no such type as “standard panel”, almost every panel is different. Please indicate an ID of the chips on the rear side of the panel.

By the way. pay attention to the reliability of the A B C D connections - the picture on the first matrix looks as if there is no contact on one of these pins.

Here is the wiring

I can identify three ICs on the back:
6124C - YCM0042
DP245D - 3H2804
TC7262FJ - NGM772000

b707, I can confirm that all connections are good on the inputs of each panel as I am able to connect each one solo and run the FeatureDemo and my code. I have not been able to confirm the outputs on either panel are functioning, but I have swapped the order and always the same results. First panel looks ok but missing every other row, second panel is more or less random output.

This is the FeatureDemo when the second panel is NOT connected. Works fine. This is what either panel looks like when not chained to the other.

My code, working on one panel:

Broken when the second is connected:

Thanks for the info.
I’m sorry, but then I have no other ideas. Based on the chips, I can say that these are just the most ordinary led-driver and multiplexer, such a matrix should work like a charm.
The only advice is to try with some other library and board.

Your ribbon cable is faulty, you can see how the red conductor (corresponding to pin 1) is on the top on one side and the bottom on the other


oooo wwwww good catch :slight_smile:

I would be forced to add meaningless letters because the forum has an unreasonable message limit of at least 20 characters. By the way, on there are only 5 characters

Yep, that was it! Thanks for pointing that out.

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