ESP8266 Community Forum

- Mon Apr 04, 2016 2:00 pm #44825 Yes, resistors value can be something like 10K or 4K7.

It is preferable to use resistors on all the pins, because you can still use them in your software, and having GPIOs permanently hook on VCC or GND can destroy them if by mistake you set them as output.

An good example of multiple purposes is to use GPIO2/GPIO0 as I2C bus, because I2C bus also requires pullups and therefore it is a perfect match with those GPIOs.

GPIO15 can still be use to blink an LED for example, as long as it has the pulldown required.

- Mon Apr 04, 2016 3:29 pm #44828

It is preferable to use resistors on all the pins, because you can still use them in your software

But if i would like to blink an LED at a GPIO pin i already connected a resistor to, i think that it just wouldn't blink at all? Because i get like 0.11mA with a 10K resistor and 3.3V output (if the LED runs with 2.2V)?

because you can still use them in your software, and having GPIOs permanently hook on VCC or GND can destroy them if by mistake you set them as output.

So they wouldn't get destroyed if i used a resistor in front of them?

- Mon Apr 04, 2016 4:50 pm #44830 For example, if the LED is connected to GPIO15, the LED itself have a current limiting resistor of about 470R or 1K, the LED can blink easily. The pulldown of 10K would be in parallel of the previous LED circuit, not in place of the previous 470R.

For the other pins, such GPIO2 with 10K pullup, if by mistake you turn GPIO2 as output with a LOW state, the 10K will simply act as a small load on GPIO, so no damage at all, but if this 10K was a wire instead, so 0R, it will completely short the GPIO to VCC and damaging it. This would be the same with GPIO15 if shorted to GND and by mistake turned to output with HIGH state.

- Sat Apr 09, 2016 8:45 am #45170 But for other pins like GPIO12, GPIO14, TX or RX i don't need an extra resistor because they are not connected to Vcc?

Is this correct now? I use a 10k resistor as a pullup or pulldown, depending on the pin.

You do not have the required permissions to view the files attached to this post.