//
// hello.speaker.45.c
//
// speaker PWM hello-world
//    square wave, pseudo-random frequency
//
// Neil Gershenfeld
// 11/14/10
//
// (c) Massachusetts Institute of Technology 2010
// This work may be reproduced, modified, distributed,
// performed, and displayed for any purpose. Copyright is
// retained and must be preserved. The work is provided
// as is; no warranty is provided, and users accept all 
// liability.
//

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

#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 cycle_delay() _delay_us(20000) // cycle delay
#define current 150 // PWM current
#define off 255 // PWM off
#define PWM_delay() _delay_us(25) // PWM delay

#define MOSFET_pin (1 << PB1)
#define MOSFET_port PORTB
#define MOSFET_direction DDRB

int main(void) {
   //
   // main
   //
   unsigned char count, pwm;
   //
   // set clock divider to /1
   //
   CLKPR = (1 << CLKPCE);
   CLKPR = (0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0);
   //
   // initialize MOSFET_pin
   //
   set(led_port, red);
   output(led_direction, red);
 
   //
   // main loop
   //
   while (1) {
      //
      // off -> red
      //
      for (count = 0; count < 255; ++count) {
         clear(led_port,red);
         for (pwm = count; pwm < 255; ++pwm)
            PWM_delay();
         set(led_port,red);
         for (pwm = 0; pwm < count; ++pwm)
            PWM_delay();
         }
}