[solved] Analog pin configuration outside of setup()

[polystyrene]

@BDub

@polystyrene

nMode() altogether for that pin. The weird thing is getPinMode() returned AN_INPUT even 500ms after the last analogRead(), but only

I just looked at the code again:

The first time analogRead() is called for a particular pin, the ADC is initialized, it will save the current pinMode() and set the new pinMode() to AN_INPUT, take 10 samples and average them, and leave the pinMode() set to AN_INPUT. Every time it's called successively it will not attempt to set the pinMode() to AN_INPUT so it is imperative not to change the pinMode() after calling analogRead() for a particular pin.

If you called digitalRead() on this pin, because you never set the pinMode() explicitly to INPUT, digitalRead() will just return 0;

If you set pinMode() to INPUT, analogRead() will do it's same sequence but now it saves the current pinMode() as INPUT. When digitalRead() is called, it knows that you originally set the pinMode() as INPUT so it changes the pinMode() from AN_INPUT to INPUT and returns the value of the pin's input register. If you called analogRead() again on the same pin, it will not switch it back to AN_INPUT.

If you set pinMode() to OUTPUT, analogRead() will do it's same sequence but now it's saving the current pinMode() as OUTPUT. When digitalRead() is called, it knows that you originally set the pinMode() as OUTPUT so it changes the pinMode() from AN_INPUT to OUTPUT and returns the value of the pin's output register. If you called analogRead() again on the same pin, it will not switch it back to AN_INPUT.

So it's only attempts to set the analog pin back to AN_INPUT mode the first time you call analogRead for a given pin.

If you explicitly set a pin to INPUT or OUTPUT after that first analogRead() call, it will not attempt to switch it back to AN_INPUT.

This sounds like exactly what you are experiencing.

Best advice I can give is don't use pinMode() with analogRead(). EDIT: just pushed a change to the docs about this.

That definitely is consistent with what I'm seeing. That clears things up greatly. Thanks again!