ESP8266 Community Forum

- Fri Dec 02, 2016 5:42 am #58998 Hello All,
I need wire Gpio2 with echo pin on hc-sr04 (ultrassonic sensor) but every time I go to download mode on power up, if i power esp without connect echo pin all works well (connecting pin after boot process)
Any hint?

Thks and sorry about bad english

- Fri Dec 02, 2016 9:10 am #59008 See if this :- http://www.instructables.com/id/How-to-use-the-ESP8266-01-pins/?ALLSTEPS
or this :- http://www.instructables.com/id/ESP8266-Using-GPIO0-GPIO2-as-inputs/?ALLSTEPS
is of any help.

- Fri Dec 02, 2016 10:19 am #59010 GPIO2 and GPIO0 need to be both HIGH to boot in normal execution mode.
If the HC-SR04 provide LOW in idle state, I would recommend to use a MOSFET as an Inverter, so in the way the idle state will becomes HIGH.