/*******************************************************************************************
* alarm.c
*
* based on hello.ftdi.c and hello.H-bridge.44.DC.c by Neil Gershenfeld
*      and button44 by Rob Hart
* set lfuse to 0x5E for 20 MHz xtal
*
* Recieves data as 1/0 and sounds alarm when active
*
* Brian Plancher
* 12/7/16
*
********************************************************************************************/

#include <avr/io.h>
#include <util/delay.h>
#include <avr/pgmspace.h>
#include <avr/interrupt.h>

// helper defs
#define input(directions,pin) (directions &= (~pin)) // set port direction for input
#define output(directions,pin) (directions |= pin) // set port direction for output
#define set(port,pin) (port |= pin) // set port pin
#define clear(port,pin) (port &= (~pin)) // clear port pin
#define pin_test(pins,pin) (pins & pin) // test for port pin
#define bit_test(byte,bit) (byte & (1 << bit)) // test for bit set
#define on_delay() _delay_us(3) // PWM on time
#define fast_off_delay() _delay_us(1) // PWM fast off time
#define medium_off_delay() _delay_us(3) // PWM medium off time
#define slow_off_delay() _delay_us(5) // PWM slow off time
#define cycle_delay() _delay_us(2) // cycle delay
#define PWM_count 20000 // number of PWM cycles
#define cycle_count 5 // number of speed cycles

// hbridge outputs for speakers
#define speaker_port PORTB // speaker port
#define speaker_direction DDRB // speaker direction
#define MOSFET (1 << PB2)
#define SPEAKER_HZ 520 // want to cycle at 520 HZ because google says that is ideal alarm sound
#define XTAL 20000000 // 20 mHz
#define SPEAKER_PERIOD (XTAL / 1024 / SPEAKER_HZ) // prescaler of 1024
#define SPEAKER_HALF_PERIOD (SPEAKER_PERIOD / 2)

// input for control
#define input_port PORTA
#define input_direction DDRA
#define input_pins PINA
#define input_in (1 << PA3)

uint8_t off(){
   clear(speaker_port, MOSFET);
   return 0;
}

uint8_t on(){
   set(speaker_port, MOSFET);
   return 1;
}

int main(void) {
   // set clock divider to /1
   CLKPR = (1 << CLKPCE);
   CLKPR = (0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0);

   // initialize input pin
   input(input_direction, input_in);
   volatile uint8_t active = 0;

   // set speaker for output and timers
   output(speaker_direction, MOSFET);
   clear(speaker_port,MOSFET);
   volatile uint8_t state = 0;
   
   // start timer1 with /1024 prescaler -- means count to 19531.25 for one second
   // and set the initial value to 0
   TCCR1B = (1<<CS12) | (1<<CS10);
   TCNT1 = 0x00;

   // main loop
   while (1) {
      active = pin_test(input_pins,input_in);
      // if not active re-set everything and clear outputs
      if (!active){
         state = off();
      }
      // else if we have done a half period switch the on off for the signal frequecny
      else if (TCNT1 >= SPEAKER_HALF_PERIOD){
         if (state){
            state = off();
            TCNT1 = 0x00;
         }
         else{
            state = on();
            TCNT1 = 0x00;
         }
      }
   }
}