change open drain to pp

[mahmoud boroumand]

Posted on February 12, 2018 at 14:26

hello 

i use this configuration for send for ws2812.

GPIO_InitStructure.GPIO_Pin = WS2812B_PINS;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_OD;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(WS2812B_PORT, &GPIO_InitStructure);

I because i need 5v i use this configuration (use 2.2K for pull up). but i now i want chage port to pp and 3.3 v and do this configuration 

GPIO_InitStructure.GPIO_Pin = WS2812B_PINS;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(WS2812B_PORT, &GPIO_InitStructure);

but i have a problem if the mcu use to open drain if i change to pp i have noise on it but if it is new i don't have any problem what can i  do?

[T J]

Posted on February 12, 2018 at 14:42

are you discussing the serial LED driver ?

its likely to work with 3V data in,. did you try it ?

you can use a transistor or FET to translate the voltage, but some configurations invert the data, some don't.

easiest is:  2 resistors, 1 npn transistor but returns an inverted output.

[AvaTar]

Posted on February 12, 2018 at 14:55

but i have a problem if the mcu use to open drain if i change to pp i have noise on it but if it is new i don't have any problem what can i  do?

If I understand this convoluted and careless punctuated sentence correctly:  Have you tried a proper de-init of the pin ?

Un-set the old pin configuration first, then set the new one.

... if i change to pp i have noise on it...

This suggests you did not really change to PP, I view 'noise' as symptom of OD without a load resistor.

[Andrew Neil]

Posted on February 12, 2018 at 15:37

if i change to pp i have noise on it

on what, exactly?

And what sort of 'noise', exactly, is it?

Post a proper schematic of your two setups, and oscilloscope traces of the signals.

Instead of changing to PP, what happens if you just set PP from the outset ... ?