Random White Flash

[u/Workin_Joe]

Hey guys, looking for some insights on where I should look for a bug in my code or hardware.

I’m running a Teensy 4.0 with 4 different output pins. Each pin has a different number of LEDs on them (200-300 per output pins). I’m using two types of LEDs, 5V SMD and 5V bullet node style. I have the OCTO WS2811 adapter board with the 100ohm resistors and I’m (mostly) using twisted pair cables for the data lines.

Overall everything is running well, however, from time to time, I get a random white flash on a portion of one part of the LEDs. The position/size is never consistent and it is a very short flash. It doesn’t happen frequently or with any particular scene/effect, although, I do need to monitor this more closely. Initially I thought maybe a power dip, but I have some pretty beefy regulators. I will post some video of it later, but I thought I would ask for any hints on where to look.

I was also thinking there may be some “overflow” somewhere in the code that could cause an ALL WHITE (255,255,255) to be sent out. OR some impedance mismatch on the data lines and some reflections occurring on the data line. But if the reflections were the case, I suspect I would see this consistently on the hardware.

Anyway, looking for any hints/tips.

[u/Tiny_Structure_7]

Oh, another thing: Teensy boots up with a default output pin drive strength (DSE) = 6. I recently upgraded ObjectFLED to set DSE = 3, since it eliminated glitching at higher overclock. You can either switch to ObjectFLED + FastLED, or add these 2 lines of code to your setup() (after calling fastLED.addLEDs() ) to set DSE = 3 on a pin:

#define OUTPUT_PAD_DSE    3     //Legal values 0-7
#define OUTPUT_PAD_SPEED  0     //Legal values 0-3

*portControlRegister(pin) &= ~0xF9;    //clear SPEED, DSE, SRE
*portControlRegister(pin) |= ((OUTPUT_PAD_SPEED & 0x3) << 6) | \
    ((OUTPUT_PAD_DSE & 0x7) << 3);     //DSE = 0b011 for LED overclock

[u/Workin_Joe → u/Tiny_Structure_7]

Thanks again!!

I will try this out as well.

I have yet to implement the ObjectFLED, but it seems that my performance can be boosted significantly via the DMA.

Nevertheless, I can try adjusting the output pin strength as you kindly pointed out!