I am considering an application with moderate amount of SPI activity (mostly tx to LCD).
Also 2 async ports, both rather low density:
...1 @ 9600 doing mostly tx at 1 Hz, short msgs, with occasional burts.
...The other is RX only 9600 at 1Hz (GPS) and can be disabled for a minute or 2 as I only need time.
My preferred target is Arduino Nano 328.
I could configure things several ways, but I think the HW IO ought to go to the SPI because it will be the highest load.
The GPS can be disabled for relatively long periods, enabled to grab current time, then disabled.
Any thoughts from experienced system designers?