ESP-01 strange behavior

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1

ESP-01 strange behavior
I am working on a project which uses pin interrupt attached to GPIO-2
The sketch is working well, if the level of GPIO-2 change ISR function is raised and it does what it should do.
But I have experienced a very strange start-up behavior:
if I push the GPIO level to LOW (e.g. with keeping a connected button ON) then I turn ON the power of ESP-01 then seems to be it goes crazy; the blue LED is lighting up and keep doing that, on GPIO-2 pin appears a continuous square signal with about 19 KHz frequency and same on Tx pin too. In the same time on GPIO-0 there is about a square signal too with about 26 KHz ! And of course nothing works.
This state remains until I set GPIO-2 to HIGH and I push the reset or switch OFF/ON the power. After that everything s are all right again and the module and the sketch on it is working well again even if GPIO-2 level is changing.
The above described behavior just happen if GPIO is LOW during startup.
Has somebody experienced same behavior?
To test if whether the sketch makes something wrong I uploaded a minimal sketch into the ESP-01 (Only Serial.begin(9600) and Serial.print("hello") is in the setup(). The behavior is same as described so no software problem is here.

Any help, suggestion is greatly appreciated.

2

Ahhh I just have found the info "during boot-up the device GPIO-2 MUST BE on HIGH otherwise unpredictable behavior can happen"

So in my project must make sure to keep GPIO-2 HIGH during boot-up.

Maybe this can be helpful for others too.

3

OR don't use that pin. If you do use it, define it as INPUT_PULLUP but first do a digitalWrite(pin2, HIGH); seems backwards I know.