Opta variant I/O pins vs analog pins

[vmsh0]

Hi,
Sorry for opening an issue; this is not an issue per se but I wasn't sure where else to ask these very specific questions about the Opta core (the Arduino forums don't look like a place where this would be very on topic).

I'm trying to understand how the pins for the Opta I1-I8 ports are mapped. From my understanding, ports I1-I8 can be set up as either ADC ports or I/O ports. This latter option, just for input.

From here, I gather that only I1 (A0) and I2 (A1) are using direct analog channels when used as I/O ports. This is empirically confirmed by measuring the HIGH output of all the pins: the first two sit at a different voltage (just below 3V), suggesting that they have slightly different electrical characteristics. (I know the experiment I have performed is unsupported; I made sure to use appropriate current limit to avoid burning the ADC pins.)

First, I don't understand is how this relates to g_AAnalogPinDescription array in the same file. In particular:

1. Why does that array map the same names A0-A7 to different processor pins? Are the physical ports of the Opta electrically connected to more than one pin on the package?
2. How is port PC_2C connected to both I2 (A1) as an I/O and I3 (A2) as an ADC? Does this mean that it is not possible to use I3 as an analog input while I2 is used as a digital input? Also, if this is the case, wouldn't using I2 as a digital input risk sinking too much current to PC_2C?

Second, I was trying to find an explanation to the manual's claim that you can't use I1 (PA_0C) and I4 (PB_0) as interrupt ports. I couldn't explain it from what I read here in the core source code, so I was hoping you could help me shed some light on that as well.

Again, sorry if this is not the correct channel to ask. I thank you in advance for your time and consideration :)

[manchoz]

Hey @vmsh0,
Please check the Pinout at https://docs.arduino.cc/tutorials/opta/user-manual/#pinout and the Programmable Inputs at https://docs.arduino.cc/tutorials/opta/user-manual/#programmable-inputs section of the User Manual.

More details regarding the multiplexed pins are available in the same document at https://docs.arduino.cc/tutorials/opta/user-manual/#interrupts