Hi!
I'm trying to design a shield for the Leonardo and I need access to 14 output pins. Can I use Pins 0 and 1 if I want to maintain a Serial connection to a computer constantly, I need to know if I can use both pins. I am wondering because the Atmega32u4 is a very different chip than the Atmega328p.
You can use pins 0 and 1 as regular digital pins and they won't interfere with your use of the serial connection to the computer. On the Leo, the USB serial connection does not use those pins at all.
You have 23 digital pins on the Leo and most other ATmega32U4-based Arduinos. Pins 0 through 13 are on the digital pin headers, pins 18 through 23 are on the analog header so if you aren't using analog inputs you can just use those as digital pins. A0 is pin 18, A1 is pin 19, and so on. And you also have pins 14, 15, and 16 on the ICSP header.
D14 MISO 1 . . 2 VCC
D15 SCK 3 . . 4 MOSI D16
RST 5 . . 6 GND
Thanks Very much