EPIC DIY 3D Printed Laser Trip Alarm

#include <avr/io.h>              //Files we need to turn the pins on and off
#include <util/delay.h>          //Files we need to make the chip wait some time
#include <avr/interrupt.h>    //Files we need to make an interrupt trigger ( ISR )

#define noteDuration  8000          //How long we want the note to play for

​

//First We Set up the Rules for the Trigger

void interruptEnable(void)  {
   EIMSK |= (1 << INT0);        //ISR enabled on INT0 pin which is PB0
    EICRA |= (1 << ISC00);        //triggers on any change in voltage
    sei();                        //enables global interrupts
    
}

​

/*Next we set up a Function to scan the amount of analog voltage coming in on our
pins connected to the analog to digital converter*/

uint16_t readADC(uint8_t channel) {      /*ADC value will be a 10 bit number made of 2x 8 bit numbers                                                                                   from each ADC pin we can call "channel" */
    ADMUX = (0xf0 & ADMUX) | channel;    //Conversion process
    ADCSRA |= (1 << ADSC);                 //Signal that it is busy doing conversion
    loop_until_bit_is_clear(ADCSRA, ADSC); //Keep at it until the job is done and all clear is given
    return(ADC);                           //give us that new digital value from that pin we scanned
}

​

/*The playNote function is confusing but you will better understand it if you play around with one value at a time*/

​

void playNote(uint16_t wavelength, uint16_t duration) {              /*this is a function that will vibrate the

                                                                                            piezo speaker based on wavelength and duration*/
  uint16_t elapsed;                                             //to remember how much time has passed during each note
  uint16_t i;                                                            //a counter
  for (elapsed = 0; elapsed < duration; elapsed += wavelength) {        

                 //This For Loop puts limits on the duration in order to create a wavelength
                                                                        
    for (i = 0; i < wavelength; i++) {                                    //This For loop with delay selects the pitch
      _delay_us(1);
    }
    PORTB ^= (1 << PB1);                                     //We alternate the pin on and off each loop to make it vibrate
  }
}

uint8_t x;                //Container for a value in our loop later

​

/*MAIN Staging Part of our code*/

int main(void) {
   
   uint16_t adcValue0;        //Like a container to hold our adcValue for later
    interruptEnable();      //Tell the interrupt to get ready
    DDRB |= (1 << PB1);     //The speaker is connected to pin PB1 and it's negative leg to a capacitor which connects to the Ground of the chip
    DDRC |= (1 << PC5);        //Turns on the pin connected to one leg of the LDR sensor, it's other leg connects to the positive voltage of the chip
    

/*This is the loop of code the chip runs over and over and over*/
while(1) {                        //while the chip is running...

    
   adcValue0 = readADC(5);        /*set that adcValue container to hold the value that pops out from the 

                                                       readADC function on ADC pin 5 (PC5) */
    _delay_us(10);                //wait 10 microseconds for it to complete
    
   if (adcValue0 < 20) {        //if the adc voltage value for the LDR is less than 20 then do...
                            //20 seems like a nice piercing pitch on our 8mhz chip (timing and speed changes sound)
         for (x = 0; x < 50; x++) {    //count up to 50 total but only add 1 each time through this loop    
       playNote(30, noteDuration);    //using our playNote function for the wavelength and duration
        PORTB ^= (1 << PB1);       // Alternate the speaker pin on and off to make it vibrate during this process
                                        
           }
                                   
         }
       
    else {                         //Otherwise...
        PORTB &= ~(1 << PB1);  //we keep the speak pin PB1 OFF and quiet
    }
}
   
return (0);                //This is just here, don't worry about it
}