Right usage of WS2812B LEDs

[FantomXR]

Hey people,

I have two questions regarding the WS2812. If you read through the internet you will find various articles that one should use a resistor between DIN of the LED and the output-pin of the microcontroller. Is that also right for the STM32F4? 

The second thing is, that the first (or sometimes an other) LED lights up short after a few seconds after powering the core (both share the same power supply). Any ideas how to prevent this?

Thanks,
Chris

[TK.]

Hi Chris,

adding a resistor (e.g. 470 Ohm) to between the core output pin and WS2812 is probably a good idea, see this posting for the arguments: https://electronics.stackexchange.com/questions/177019/why-does-a-resistor-in-my-neopixel-data-line-work-at-all

The LED should turn off once the Core starts to drive data into the chain.
Enable the "fastboot" option so that this happens as fast as possible

Best Regards, Thorsten.

[FantomXR]

Dear TK,

thanks for your reply. Alright, I'll add this resistor.

For the other "problem" I'll try to add a hardware delay with RC circuit to prevent the LED from flashing.