How many digital output are really available on Arduino Uno?

Projects General Guidance
1

Hello,

I'm new in Arduino world and trying to develop a MIDI interface for playing vintage electronic musical instruments.

My question is: how many digital output are available at maximum on the Arduino Uno? I've read 14 in the specs, but I see they are physically more:

0,1 are used for RX/TX
2 to 13 are digital I/O, right? -> then 12 digital I/O (not 14)
I see 2 pins at the end which are not referenced on the board (just after AREF), are they digital I/O?
Analog in A0 to A5: can they be used as digital I/O, or are they fixed as analog inputs?

In fact, at best I need 17 digital outputs, is it possible with Arduino Uno?

Thank you for any advices,

Patrick

2

Quoting Pololu - Arduino Uno DIP Edition,

The Arduino Uno is a microcontroller board based on the ATmega328. It has 20 digital input/output pins (of which 6 can be used as PWM outputs and 6 can be used as analog inputs)

I've read that in the past elsewhere.
Basically, there's 20 IO pins.

  • 6 will work with PWM - AnalogWrite - D3, D5, D6, D9, D10, D11
  • 6 will work with anaolg input - AnalogRead - A0, A1, A2, A3, A4, A5
  • 20 of them will work with DigitalRead/Write. D0, D1, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12, D13, A0, A1, A2, A3, A4, A5

More here:
http://arduino.cc/en/Hacking/PinMapping168 (applies to Atmega328 too)

3

tuchap:
Hello,

I'm new in Arduino world and trying to develop a MIDI interface for playing vintage electronic musical instruments.

My question is: how many digital output are available at maximum on the Arduino Uno? I've read 14 in the specs, but I see they are physically more:

0,1 are used for RX/TX
Yes, but if your not using serial commands in your sketch you can use pins 0 and 1 as regular digital pins
2 to 13 are digital I/O, right? -> then 12 digital I/O (not 14)
Again pins 0 and 1 are available if you don't require serial in your sketch.
I see 2 pins at the end which are not referenced on the board (just after AREF), are they digital I/O?
Analog in A0 to A5: can they be used as digital I/O, or are they fixed as analog inputs?
Yes they can be used as digital pins.
pinMode(A0, OUTPUT);
digitalWrite(A0, HIGH);

In fact, at best I need 17 digital outputs, is it possible with Arduino Uno?
Yes, even without using pins 0 and 1, D2 to D13 and A0 to A5
Lefty

Thank you for any advices,

Patrick

4

Thank you for your useful answers, appreciated!

It's clear now.

Patrick