ESP8266 Community Forum

- Thu Jun 04, 2015 3:34 am #19433 Just saw what GPIO15 is about, from:
https://github.com/esp8266/esp8266-wiki/wiki/Boot-Process

GPIO15 being HIGH on startup selects boot from SD card, so it should be connected to GND normally (on startup):
https://drive.google.com/file/d/0ByLNRzaQc0jPV0xaektpdFFoMGs/edit

Hermann.

- Thu Jun 04, 2015 3:50 am #19434 If GPIO15 should be used after startup, direct connection to GND would not be good, right?

So shouldn't GPIO15 be pulled LOW via a resistor as GPIO0 is pulled HIGH?
(from http://internetofhomethings.com/homethings/?p=286):


Hermann.

- Thu Jun 04, 2015 8:25 am #19436 Yes, you are correct, you should use a resistor to pull GPIO15 to GND. Depending on what you are doing with the LED on GPIO2 you might want to adjust that resistor value. I don't recall the drive strength of the ESP8266 but putting 10mA through the LED is usually more than enough to make it bright. Just use Ohms law (V=IR), where V in this case is 3.3-Vf and Vf is the forward voltage of the LED you're using.

- Thu Jun 04, 2015 12:13 pm #19447 Doesn't that LED plus resistor on GPIO02 cause the unit to boot in the wrong mode?