/*
 * scheduler.c
 *
 * Description:
 * This is a demonstartion of a simple scheduler for CCS PICC compiler.
 *
 * Author: Martin Dubuc
 * http://members.rogers.com/martin.dubuc/Robotics/Tips.html
 *
 * Creation date: November 18, 2003
 */

#include <16f877.h>

/* Microcontroller configuration bits */
#fuses HS,NOPROTECT,NOWDT,BROWNOUT,PUT,NOLVP

#ORG 0x1F00,0x1FFF {} /* Reserve memory for bootloader for the 8k 16F876/7 */

#device *=16 /* Allow RAM to expand beyond 256 bytes */

/* Set the clock speed to 20 MHz. */
#use delay(clock=20000000)

/* Directive for RS-232 interface */
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)

/* Pin definitions */
#define LED0 PIN_B4
#define LED1 PIN_B5
#define LED2 PIN_B6
#define LED3 PIN_B7

// Scheduler variables
unsigned char t1mS = 0,
  t10mS = 0,
  t100mS = 0;
             
unsigned char t1mS0 = 0,
  t10mS0 = 0, 			// Watchdog timer kicker
  t10mS1 = 0,                   // LED blinking (quarter second on/off)
  t100mS0 = 0,                  // LED blinking (half second on/off)
  tS0 = 0,                      // LED blinking (1 second on/off)
  tS1 = 0;                      // LED blinking (2 second on/off)

/* Function prototypes */
/* Public interface */
void main(void);
void init_pins(void);
void init_timers(void);
void init(void);
void timer1_isr(void);

/* Scheduler implementation */

/* Init hardware pins: Set up the TRIS and set the pins to their
 * default values.
 */
void
init_pins(void) {
  /* Set up the various pins in/out */
  set_tris_b(0b00000000); /* B4 to B7 are outputs. Rest are not used. */

  /* Set initial condition for servos */
  output_low(LED0);
  output_low(LED1);
  output_low(LED2);
  output_low(LED3);
} /* init_pins */

/* Module initialization. Initialize pins, global variables,
 * interrupts and timers.
 */
void
init(void) {
  init_pins();

  init_timers();

  // Enable Timer1 interrupts
  enable_interrupts(INT_TIMER1);
  enable_interrupts(GLOBAL);

  printf("Scheduler demo\r\n");
} /* init */

/* Initialize the Timer1 timer. */
void
init_timers(void) {
  // Configure Timer1
  // Timer1 used for fixed 1 ms clock interrupt
  // For 20 MHz, base/4, prescaler/8 here and ~/625 in ISR
  setup_timer_1(T1_INTERNAL | T1_DIV_BY_8);
} /* init_timers */

/* This is the main control loop. */
void
main(void) {
  init();
  
  for ( ; ; ) {
    if (t1mS0) { /* 1 ms have elapsed */
      t1mS0 = 0;
    }

    if (t10mS0) { /* 10 ms have elapsed */
      /* Kick the watchdog. */
      RESTART_WDT();
    }

    if (t10mS1 == 25) { /* 250 ms has elapsed. */
      t10mS1 = 0;

      /* Toggle LED */
      output_bit(LED0, !input(LED0));
    }

    if (t100mS0 == 5) { /* 500 ms has elapsed. */
      t100mS0 = 0;

      /* Toggle LED */
      output_bit(LED1, !input(LED1));
    }

    if (tS0) { /* 1 second has elapsed */
      tS0 = 0;

      /* Toggle LED */
      output_bit(LED2, !input(LED2));
    }

    if (tS1 == 2) { /* 2 seconds have elapsed */
      tS1 = 0;

      /* Toggle LED */
      output_bit(LED3, !input(LED3));
    }
  }
} /* main */

#int_timer1
void timer1_isr(void) {
  // Clock interrupt service routine. Invoked on Timer1 interrupt.
  set_timer1(-625);	// For 20 MHz/625 => 1 ms - latency

  t1mS0++;
  if (t1mS++ == 9) { // 10 ms
    t1mS = 0;
    t10mS0++;
    t10mS1++;
    if (t10mS++ == 9) {	// 100 ms
      t10mS = 0;
      t100mS0++;
      if (t100mS++ == 9) { // 1 s
        t100mS = 0;
        tS0++;
        tS1++;
      }
    }
  }
} /* timer1_isr */