ESP8266 Community Forum

- Tue Jul 21, 2015 5:27 pm #23872 Using a different board than the ESP8266-01 fix the problem?

- Tue Jul 21, 2015 5:53 pm #23874 All the Source/Sink explanations above not only apply to any kind of ESP, but to any MCU or plain logic chip in general.
Also, as a side note, some IC can provide much higher SINK current than SOURCE.

- Wed Jul 22, 2015 9:24 am #23926

Here are some images from the Web.

Sourcing a LED has the effect of pull-down, not good it the current case :


Sinking is acting like a pull-up, but the side effect is that logic is reversed, software setting GPIO to "1" turn off the LED while "0" make it glowing :

This is great. It works for me with this setup.
The problem I have now is that when it boots up, the led is ON, even though I set the pin to HIGH at void setup.
I am using Blynk and I cannot find a basic guidance how to invert the pin logic.
Is there another way to make the LED off after it boots up?
Thanks !

Do you feed the LED from 5V or 3,3V? If the Led is feed from 3.3V and the GPIO is HI it can't be on.

- Wed Jul 22, 2015 9:50 am #23928 If I recall correctly, I used 3V and 220 Ohm resistor and it was working fine.
Anyway, I have given up on the esp8266 as I am more interested in the esp12 with more GPIOs.
I no longer have this issue with esp12 since I am no longer using GPIO2.