ESP8266 Community Forum

A voltage divider is the only option to read higher voltages, but If you want reliable readings then OPT for another A>D connected via the I2C bus or similar that has multiple inputs, lets face it nowadays we need more than one analog channel.

I believe the ESP8266 A>D is used for RSSI readings from the RF stage when Scan AP mode is operative! and ReadVCC.

Dans

Dan I'm not following what you mean here . Do you have any references that you have seen on it . I would like to put it in the Wiki

martinayotte I have put your graph there for starters Thanks

@tytower,
Let me see if I could shed some light on the ESP's ADC pin.

1) The Arduino reports a range of 0 to 1023 to correspond with 0V to 5V. The ESP reports 0-1023 to correspond with 0V to 3.3V. This is just the way the chip was designed, no way to change it.
2) However, by using a voltage divider, we can adjust any higher voltage to get around that limitation.
Here's a diagram I found on Instructables.

On my circuit, I did not wire my potentiometer like the pictured breadboard, instead I used a 10K potentiometer for R2 (the bottom resistor that is connected to ground), and a 23K fixed resistor for R1 (the side that is connected to 3.3V). Doing so, the voltage at the Vout junction ranges from 0V to 1V which corresponds to 0 to 1000 or so upon analogRead(A0). I did not get 1023, I suspect that's due to lack of precision on my resistors.

hwiguna wrote:@tytower,
Let me see if I could shed some light on the ESP's ADC pin.

1) The Arduino reports a range of 0 to 1023 to correspond with 0V to 5V. The ESP reports 0-1023 to correspond with 0V to 3.3V. This is just the way the chip was designed, no way to change it.
.

You are not making this any clearer unfortunately ....which is it
"The ESP reports 0-1023 to correspond with 0V to 3.3V." or
"The ESP reports 0-1023 to correspond with 0V to 1.0.