Debutton.c

/////////////////////////////////////////////////////////////////////////////
// Basic HC9S12 Output Compare Timer Functionality
/////////////////////////////////////////////////////////////////////////////

#include <hidef.h>      /* common defines and macros */
#include "derivative.h" /* derivative-specific definitions */

#include "pll.h"
#include "swled.h"

void Wait10ms();  //Wait for 10 ms
int DebouncedButtonState(eSWLSwitch butt); // return the current debounced state of the button

/////////////////////////////////////////////////////////////////////////////
// Main Entry
/////////////////////////////////////////////////////////////////////////////
void main(void)
{
  int LastState = 0;  //Previous button state
  int CurrState = 0; //The current button state 
  // main entry point - these two lines must appear first
  _DISABLE_COP();
  EnableInterrupts;
  
  /////////////////////////////////////////////////////////////////////////////
  // one-time initializations
  /////////////////////////////////////////////////////////////////////////////
  PLL_To20MHz();
  (void) SWLInit();

  //Initialize Timer.  OC0
  // Turn the thing on
  TSCR1 = 0b10000000; //TSCR1_TEN is bit 7.  Turn it on. 7.3.2.6
  // Set Prescale of 128
  TSCR2 = 7; //0b00000111;  //Timer rate = BUSSPD/2^7 = 20 MHz/128 = 156.25 KHz (6.4 us tick) 
  // Use channel 0 OC
  TIOS |= 0b00000001; //1
  // Toggle the pin for channel 0 (pin 9)
  TCTL2 = 0b0000001;
  //Main loop
  for (;;)
  {
    CurrState = DebouncedButtonState(SWLMiddle);
    if(CurrState != LastState) //Button has changed
    {
      //Either button was pressed or button was released
      if(CurrState)//Pressed!
        SWLSet(SWLAll);
       else
          SWLClear(SWLAll);
      //else //Released!
      //Do nothing
    }
    LastState = CurrState;
  } 
}

/////////////////////////////////////////////////////////////////////////////
// Functions
/////////////////////////////////////////////////////////////////////////////
void Wait10ms()  //Wait for 10 ms
{
  //Timer for OC0 is currently set up. Let's use it.
  // 1 - Clear any pending flags
  TFLG1 |= 0x00000001; // Yes, 1 clears.  Not 0

  //Arm for an event in 100 ms
  TC0 = TCNT + 1563;// 10 ms / 6.4 us = 1563

  while(!(TFLG1 & 0x00000001));
}
int DebouncedButtonState(eSWLSwitch butt) // return the current debounced state of the button
{
  int firstButtonState = 0;
  int secondButtonState = 0;
  do
  {
    firstButtonState = SWLRead(butt);
    Wait10ms();
    secondButtonState = SWLRead(butt);
  } while (firstButtonState != secondButtonState);
  return firstButtonState;
}
/////////////////////////////////////////////////////////////////////////////
// Interrupt Service Routines
/////////////////////////////////////////////////////////////////////////////