Panel doesn't display - But works

Hi there, Firstly, thank you for your help. I have a bit of a mystery I need some help with.

A little back story: I bought a few panels off Alibaba, thinking that this should be a fairly easy project having some experience building my own led - matrix. It’s now been 3 weeks and I haven’t gotten the panel to display anything at all … at least not in any expected way. My first thought was that it’s broken. Tested every panel, and all the panels are all the same.

After trying this repo first with no success, I built a really basic (and slow) example in arduino to test the panels. No luck there either. Still a black panel.

Finally I got the panel to display something when I “Glitched” out the power on the arduino (plug and unplugged, causing intermittent EMF on the lines). Suddenly the panel was alive, with random colours, but not behaving at all. Any normal/expected code for a panel like this didn’t work or change the behaviour in a way I thought it would. eg.

  • The panel displayed leds regardless of OE high or OE low (keep in mind there is NO clock signal or changing lines)
  • Latch (or strobe) did nothing, in sync or not in sync with the clock
  • All input data was being ignored (leaving RGB 1 and 2 all high or low, still showed random colours)
  • Putting OE on a clock did change the data being displayed and even repeated the data every few cycles, but it was not respecting the data being sent.

At this point I complete reverse engineered the board to see if I could figure out the issue. There isn’t any surprises there

  • 3 x MW245B Transceiver
  • 1 x TM74HC04 Inverter (for the driver rows)
  • 8 x SM5166P LED Driver
  • 24 x SM16259 Constant current shift registers

I’ve probed the panel and everything seems correct (the right voltages , and within spec of the datasheets I could find). The only issue is that the SM16259 is not dropping the output pins low when it should be displaying a pixel.

I did discover the SM16259 is not a normal shift register (at least to me) as it has “Scattered PWM” and “Sweep frequency multiplication Technology”

Here are datasheets I could find (can’t post all the links due to account resitrictions)
SM16259 Current drivers:
Chinese Datasheet (partial)
SM5166P Chinese

Any help would be magic. Even guesses at this point or things to try would be amazing.

The panel is 64x64 P3
Model number L3-B 32S 64x64 2121-V2.3

1 Like