the wiki here says http://www.esp8266.com/wiki/doku.php?id=esp8266_gpio_pin_allocations

0 Low
1 High
x floating
MODE                   GPIO15   GPIO0   GPIO2
SDIO (BootSDCard)       1       x        x
UART (UploadCode)       0       0        x or 1
FLASH (NormalRunning)   0       1        x or 1 

Can connecting my GPIO 2 to a servo Signal Wire cause it to go LOW? because some how my ESP8266 doen't boot when I have a servo hooked up to it. I tried to change it to RX (which is GPIO3 on ESP8266) and everything seems to work fine. But I wanna know the reason why GPIO2 didn't work.

Thank you.

p/s:http://www.goodluckbuy.com/ld-1501mg-metal-gear-digital-servo-17kg-for-rc-robot.html this is the servo, if it matters. Also GPIO-2 works when I use another servo of different type instead (I don't know its name though)

  • 2
    only one conclusion: the servo pulls the input down
    – Juraj
    Mar 8, 2018 at 11:23
  • 1
    add external pull-up to io 2
    – Juraj
    Mar 8, 2018 at 13:26

1 Answer 1


It's what Juraj said.

add external pull-up to io 2 -Juraj

sovled it

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