Switched from Pi 3B+ to Pi 4 - random lights at boot

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Today I replaced my Raspberry Pi 3B+ with a Raspberry Pi 4B. My matrix display is connected to the first chain (the Smiley :smile: configuration on the wiring howto) - same as it was on the 3B+.

When I boot my Raspberry Pi 4, a row of LEDs lights up on boot and it stays on until I actually start displaying something. The same also happens on every reboot. This did not happen with the older Pi.

This is not a showstopper in my case, but if anyone knows an easy solution (or can give me hints on how to further debug this), I’d be all ears!

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yes, I’ve seen that if you have a floating line. Probably one of the data lines goes to an rPi pin that is not initialized and sending data that causes this.
I would make sure you have all your rPI drivers on those pins, turned off.
You could also try connecting to the 2nd chain instead to use other pins.

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thank you for your reply! It is not bothering me much, but I might try using the second (:boom:) set of ports at some point. I was just curious if i broke something :smiley: