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Topic: Interrupt Issues, Interrupt 5 not working (Read 438 times) previous topic - next topic


Hello. I am new to Arduino, but very excited to be using it. It has been very simple in all other aspects until I tried to use the interrupts. I have a PIR motion sensor (http://www.robotshop.com/productinfo.aspx?pc=RB-See-194&lang=en-US) attached to the arduino mega 2560 ADK R3 board (http://arduino.cc/en/uploads/Main/ArduinoADKFront.jpg). I have connected the motion sense pin of the sensor to pin 18 (interrupt 5) of the board. Have confirmed the pin out and I have confirmed that the pin does in fact go high for about 3 seconds when motion is detected. I have confirmed this with a volt meter and I have connected the pin to the analog A1 input to read the voltage. So it is fully functioning. However when I connect it to pin 18 and set up the pin for the interrupt I cannot get it to detect the rising edge of the motion sense pin and call the ISR. I have tried to move the pin to interrupt 0 and interrupt 1. I cannot use these pins in my design because I intend to use those ports for communication with other devices. The following is my code that I am trying to use.

Can anyone give me an idea of what I am doing wrong?

Motion Sensor Code

int motionPin = 18;
volatile int motionSensorState = LOW;

void setup(){
// Open serial 0 communications and wait for port to open:
//Serial port 0 will be used to send debugger messages to the PC
//that is connected via the USB port.

pinMode(motionPin, INPUT);
attachInterrupt(5, pin5isr, RISING);
Serial.println("Motion Sensor Pin configured");

void loop() {
Serial.println("Motion Detected");
motionSensorState = LOW;

void pin5isr()
  motionSensorState = HIGH;


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Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.


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