ADC voltage limits

[phfbertoleti]

Hi there!

Please, would anyone inform Heltec LoRa Wifi (V2) ADC voltage limits?

Also, is there any restrictions to any ADC channels when using LoRa?

Thanks in advance

[Supporter]

@phfbertoleti
Please refer to this content:

Heltec esp32 wifi kit, example to read a voltage

Hi Bravos I think any analog pins can be used as ADC input (green label in pinout diagram). What’s the problem you have? Can you provide some more details? Anyway, two things you need attention: The ADC maximum input voltage ≤ 2.5V, don’t over that value, or the ADC converter will be broken. [image] If the input voltage is already bigger than 2.5V, you need to have such a voltage dividing circuit: [image] The value of R10 and R12 may need change to fit your needs. [image] :smile…

As the datasheet shown, the maximum input voltage on ADC(GPIO13) is 2.5V, so we can use the formula calculation the maximum VDD is 8V

[phfbertoleti]

@Supporter, considering module schematic, gpio 13 on the module is directly wired to esp32 gpio 13, right?

Also, official esp32 documentation says max voltage can be configured to 3.3V depending on gain condiguration. See: https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/peripherals/adc.html

Therefore, am I right in saying 3.3V can be allowed as max voltage in adc?

[Supporter]

Yes, that’s ESP32’s GPIO13

Can you please show me where says max input is 3,3V?

[phfbertoleti]

Sure. This refers to ADC2 channels. Please, see picture attached.

[Supporter]

Yes, that’s your answer