Using same number fora analog and digital pin

Forum 2005-2010 (read only) Hardware Interfacing
1

Hi guys,
i have the following problem.
An analog input on analogic pin 2 and a digital output on the digital pin 2.
Now if i read analog value from the pin 2 the value is corrupted. If i exclude the digital pin 2 the value is correct.
How it works?

2

Analogue pin 2 is a different physical from digital input / output pin 2. So doing an analogue read to pin 2 will not be affected by anything that is on digital pin 2.

Read: http://arduino.cc/en/Tutorial/HomePage

3

Yes i think so, but how can the system know that pin 2 is different?

I cant't do:
pinMode(2,INPUT); //for analog input
pinMode(2,OUTPUT) //for digital out

analogRead(2);
digitalWrite(2,HIGH);

4

You can't do analogRead() on a digital pin - as soon as you use this function the arduino assumes you mean the analog pin is what you mean.

You don't need to use pinMode() for the analog pins - it's handled automatically be the arduino. Although it doesn't really affect anything if you do include it, it can only confuse you later, so make it a habit not to include it.

The small snippet of code you included (by the way - use the '#' button when including code, makes everything look nicer), you are actually setting digital pin 2 to be an input, then straight away making it an output.

5

So just to make it clear:-

// pinMode(2,INPUT); // no need for this for analog input
pinMode(2,OUTPUT) //for digital out

analogRead(2);
digitalWrite(2,HIGH);

WILL use different pins on the Arduino.

If you want to use the analogue pins as digital input / output you refer to them as Pin 14, 15, 16, 17, & 18.

So:-

pinMode(16,OUTPUT) //for digital out

analogRead(2);
digitalWrite(16,HIGH);

WILL confuse the system because here you are asking the same pin to be an analogue input and a digital output.

When all else fails read the link I posted.