#240 DigitalInputWithAnalogPins

Demonstrate how analog pins can also be used as a digital GPIO

Notes

This is a simple demonstration of a tip shared by peter@txplore.com in the Arduino Tips and Tricks email newsletter

On the Arduino Uno, there are 6 analog pins. While we’d normally use AnalogRead to read A/D values and AnalogWrite to write PWM, they can also be used as GPIO digital pins.

The conventional analog pin mnemonics can be used:

pinmode(A0, INPUT);
int in = digitalRead(A0);

If desired it’s also possible to use the raw pin number (if driving pins algorithmically for example). Pin definitions are found in the pins_arduino.h. For the Uno, the

To use them as digital inputs, just use this reference table:

Using the pin number explicitly:

pinmode(14, INPUT);
int in = digitalRead(14);

Example

The DigitalInputWithAnalogPins.ino sketch is a simple exercise of analog pins A0..A5 using both digital input and output.

Five pins A0..A4 are set to sequentially drive corresponding LEDs at about 5mA.

A push-button is read on A5. Pressing the button reverse the LED sequence.

Construction

Credits and References

• Arduino Tips and Tricks email newsletter
• AnalogInputPins - arduino.cc tutorial
• DigitalRead - arduino.cc reference
• ..as mentioned on my blog