ESP8266 Community Forum

- Wed Sep 18, 2019 12:06 pm #83832 Hi, I have a relay module for ESP-01 and when I power it the relay close and open (because IO0 state is high at startup for short time)....

Is any way to do that no high output for IO0 at startup?



Thanks!!

- Fri Sep 20, 2019 2:14 am #83856

Is any way to do that no high output for IO0 at startup?

No, GPIO0 has to be pulled high at boot to enable running-mode: a low-state would set the ESP into upload-mode.

ESPModes.png

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Assumption is the mother of all f*ckups. At least: that's what I'm assuming.

- Mon Oct 14, 2019 8:57 am #84157 Hi, but... I have this board, the board of the pic in the main post.... when power on the board the relays turn on and off.... this is the "trouble that I have".... the IO0 for a while, when power up ESP8266 it get high state for a short time.... enough to energize the relay....

- Thu Oct 17, 2019 2:42 am #84198 Read this post: GPIO Pin states after reset/during startup:

Hey,
GPIOs 4 and 5 are the only ones that are always high impedance. All others do have internal pull-ups or are even driven low/high during boot.

GPIOs 3, 12, 13 and 14 pulled HIGH during boot. Their actual state does not influence the boot process.

GPIOs 0, 1, 2 and 15 are pulled HIGH during boot and also driven LOW for short periods.
The device will not boot if 0, 1 or 2 is driven LOW during start-up.

GPIO 16 is driven HIGH during boot, don't short to GND.

Or this one: On powerup, GPIO state, relay drive problem
Or even this one: Prevent GPIO 2 keep in High voltage when reboot ESP8266
This topic as well: ESP8266-01 Boot up GPIO spike

And there are many, many more topics about this subject...

Assumption is the mother of all f*ckups. At least: that's what I'm assuming.