Pin 6, TOUT
ADC pin. It can be used to test the power-supply voltage of
VDD3P3 (Pin3 and Pin4) and the input power voltage of TOUT
(Pin 6). However, these two functions cannot be used
The ADC for external signals is limited to 1v MAX; therefore there must be an internal voltage divider when sampling it's own power supply.
Also, it appears that micropython supports sampling of the power supply thru scaling:
pot.atten(ADC.ATTN_11DB) #Full range: 3.3v [Where "pot" is the pin object of the ADC.
Can anyone confirm that the information I've found regarding sampling the ESP8266 supply power is correct?