zum Abschluß und Einsicht für alle die vielleicht auch mal diese Info brauchen.
Das hatte ich gefunden...: ( ESP8266 )
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.