ESP8266 Community Forum

I'm feeding my ESP8266-01 using 2x1.5V battery and have connected GPIO0 to Vcc. When using AnalogRead, I get the value 214 and not 1023 as I would expect.
What should I do to get the correct value on this pin?

Thanks in advance

Lars Bo Wassini

there is no analog read on gpio0 or any other gpio of esp8266.
the only pin you can read any analog value is TOUT/ADC0/A0 whatever naming convention you are using.

AND since this pin is not accessible on ESP-01, the only value you can read is VCC

The ESP-01 doesn't have the TOUT port connected to the outside, so when reading, you're measuring the power supply (relative to 0V..1V I believe).
Though you should first turn off WiFi when performing a read and the ESP actually works at 3.3V, not 3V so your milage may vary.

As mentioned, TOUT isn't available on ESP-01 ...
What you can do is to use GPIO0/GPIO2 as an I2C bus and attach I2C ADC such MCP3431.