Using P9 as ADC input when using PyTrack

[tholden]

Hello

I dont understand the documentation regarding the ADC. Right now I am looking at the LoPy datasheet and it clearly indicates that P9 is useable as ADC in.

However, in the docs about the ADC, it says P13-P20

What is correct here?

And... I find it a bit strange that you dont have access to a single adc input from the external header on the pytrack if what is in the documentation is correct, and not the lopy datasheet.

[livius]

@tholden
To see some info about problems with ADC which @jmarcelino pointed
here is the link to issue report
https://github.com/espressif/esp-idf/issues/164
and also interesting
https://github.com/espressif/arduino-esp32/issues/92

[jmarcelino]

@tholden
P9 - as the data sheet shows - is part of ADC2 but this isn't available yet due to missing low level software support. It's planned to come to ESP-IDF later I the year.

For now you need to use ADC1 ports, i.e. P13 - P20

That said I'd recommend an external ADC connected via I2C or SPI which should plug into the available pins. The internal ADC suffers from calibration issues so, at least for my purposes, was never really useful.