P10 outdoor skipped lines and looped character

1

Hi all, I have a 320x160mm panel from LED-Card P10 Outdoor SMD LED Module - LED-CARD Shopping

I got the multiplexing to work by setting the value to 9, and then rows and columns to 16x32 but I’m seeing some graphical artifacting with skipped lines and it looks like a looped top row wrapped around to the bottom.

This is supposed to say “hello demo”:

My initial thought was that the font might be broken but I tried a few of them. None fit the exact correct dimensions and it seems like a lot of work to create a new font.

Any suggestions? Thank you!

2

This is what I have set in options:

options = RGBMatrixOptions()
options.rows = 16
options.cols = 32
options.chain_length = 1
options.multiplexing = 13
options.hardware_mapping = 'adafruit_hat'

And the text is THIS IS A DEMO! HELLO WORLD!.

Changing the chain length seems to fix some of the repeating lines, but it then gives me a sort of “stretched” version where the center of the display has the text alright except the top is cut off, and the top and bottom couple rows are bigger versions of the text. It’s as if it’s drawn multiple times.

3

looks like you’re missing one line out of two? If so, it looks like the LSB bit of the address line (I think it’s A, unless it’s D, I forget), isn’t going through. Maybe your adapter is bad, miswired, or a cable is bad.
I suppose you might also have a bad kernel option that is preventing the GPIO you need, from working.
It’s a bit easier if you use the electrodragon active-3 board since you have 3 channels and you can easily see if one channel if bad, or if your cabling is bad

4

Thanks for taking a look, @marcmerlin.

looks like you’re missing one line out of two? If so, it looks like the LSB bit of the address line (I think it’s A, unless it’s D, I forget), isn’t going through. Maybe your adapter is bad, miswired, or a cable is bad.

It seems to be both missing the line and then doubling on others, or seeing some rotation / modulo effect on lines. Other tests I did showed that it can address all lines (here’s another test writing a solid color to all panels: https://photos.app.goo.gl/QxSt82SwPZqvhP6K9, and here are a few showing similar “rotating” / offset behavior: https://photos.app.goo.gl/ogjGorRAZgPew8xd6, https://photos.app.goo.gl/tys78Yezu3L9UyTJ9).

It’s a bit easier if you use the electrodragon active-3 board

I have an Adafruit RGB Pi Hat - I can try to order one of these if you think it will help.

Is there a guide anywhere on how to diagnose these issues? I tried a bunch of different options with various different behavior, but I don’t understand the internals of the library enough to debug the issue.

Adam

5

I’m sorry, no, there is no guide. This is a project for hackers, and users may have to do some diagnosing in cases like this, including tracing lines to see a signal gets there at the rPi and/or gets lost along the wire, be able to swap for another panel or another working controller to help narrow down issues like this
Good luck