ESP8266 Community Forum

- Sun Jun 10, 2018 6:48 am #76379 I programmed two ESP's (esp-7 and esp-12) for wifi interaction and deep sleep without connecting GPIO15 to GND. This worked fine. And they still do. A third module (esp-12) did not. Why?
Is it necessary to use a resistor or can GPIO15 directly be tied to GND, if not used.

- Sun Jun 10, 2018 3:56 pm #76386 Normally one puts a medium value pull down (~4k7) on GPIO15 to GND to ensure it is correct 0 state at boot to get normal run mode. Although it is possible to skip the resistor and tie direct to GND this is not very good practice as a program could set GPIO15 to output and set it high. I know people will say I won't do that but mistakes can be made.

- Sun Jun 10, 2018 6:41 pm #76391 Shorting 15 to and is not a good idea. On most of my boards I have an led on 15 and it will often be on when in bootloader. (don't know why)