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[on:]

Hi,

I have wrote a simple program that tests external interrupts.

tx is connected to the gate of a mosfet and pin2 is the input of a square wave that goes up and down twice on each loop.

Here is the code:

int tx = 12;     
volatile int x = 0;

void setup()
{
  Serial.begin(9600);
  pinMode(tx, OUTPUT);
  attachInterrupt(0, increment, RISING);
}

void loop()
{
  digitalWrite(tx, HIGH);   
  delay(10);
  digitalWrite(tx, LOW);

  Serial.println(x, DEC);
  delay(1000);
}

void increment()
{
    x++;
}



When i dont turn my circuits battery on, the output is:

1
2
3
4
5
6
7.....

When it is on it is

1
345
346
600
623
689
1100...

Why am i getting such weirdness?

Surely when my external battery off and the external circut recieves no power, the input pin (2) should always be low and the output should be:
0
0
0
0
0
0

when it is on it should be
2
4
6
8
10...

I am totally confused by this.

Any tips or suggestions would be appreciated.

Thanks

[Reply #1 on:]

It sounds to me that you don't have some grounds connected. Post a schematic.