Digital Pin Problems


A quick question.

I am writing a sketch, and am starting to run some test on it, but it is giving me issues.

To check what I have done, I downloaded this small sketch:

int ledPin = 13;                 // LED connected to digital pin 13

void setup()
  pinMode(ledPin, OUTPUT);      // sets the digital pin as output

void loop()
  digitalWrite(ledPin, HIGH);   // sets the LED on
  delay(500);                  // waits for a second
  digitalWrite(ledPin, LOW);    // sets the LED off
  delay(2000);                  // waits for a second

This works and flashes the onboard LED.

If I attach a LED and series resistor to PD7 it does not flash. Even if I move it to another pin, and change change the pin allocation, it still does not give any O/P. I have checked the pins with a DMM and all I get:

Vcc - 0v 5v
PD7 - 5v 0v
PD7 - 0v 0v

It is almost as if the Dig pins are tri-stated

Any ideas?


If I attach a LED and series resistor to PD7 it does not flash.

Can you please explain what you mean by PD7 ? What value of resistor are you using ?

Did you make this change ?
int ledPin = 7;

What resistor did you use?


No schematic and an inadequate verbal circuit description. Try again, a bit more thoroughly.

Here's a hint: LEDs and resistors have two wires sticking out of them, meaning that each of them will be connected to two different things, not one.

A schematic drawing is best, but if you must use a verbal description then explain it to us like we're 5 years old.

You also post two measurements in each of the rows, without mentioning what the left and the right one mean.

GFuys and gals

I appear to have made an erroneous assumption (again). Your reply, LarryD, pointed me directly to my error

Thank a lots guys