timer.c

/*! \file timer.c \brief Timer Support Library for AT91SAM7S. */
//*****************************************************************************
//
// File Name    : 'timer.c'
// Title        : Timer Support Library for AT91SAM7S
// Author       : Pascal Stang - Copyright (C) 2005-2006
// Created      : 2005.05.26
// Revised      : 2006.07.27
// Version      : 0.1
// Target MCU   : Atmel ARM AT91SAM7S Series
// Editor Tabs  : 4
//
// NOTE: This code is currently below version 1.0, and therefore is considered
// to be lacking in some functionality or documentation, or may not be fully
// tested.  Nonetheless, you can expect most functions to work.
//
// This code is distributed under the GNU Public License
//      which can be found at http://www.gnu.org/licenses/gpl.txt
//
//*****************************************************************************

// system includes
#include "at91sam7s64.h"
// local includes
#include "processor.h"
#include "timer.h"
// project includes
#include "global.h"

typedef void (*voidFuncPtr)(void);
volatile static voidFuncPtr TimerIntFunc[TIMER_NUM_INTERRUPTS];

// counter/timer registers
volatile DWORD TimerPauseReg;
volatile DWORD PitCounter;


// functions
void delay_us(unsigned long t)
{
    // this function is not yet calibrated
    while(t--)
    {
        asm volatile ("nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n");
        asm volatile ("nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n");
        asm volatile ("nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n");
        asm volatile ("nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n");
        asm volatile ("nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n");
        asm volatile ("nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n nop\r\n");
    }
}

void timerInit(void)
{
    int i;
    // initialize interrupt handlers
    for(i=0; i<TIMER_NUM_INTERRUPTS; i++)
        timerAttach(i,0);

    // initialize various timers

    // default PIT setup is 1000Hz or 1ms interval
    // This default is for code compatibility,
    // simply call timerInitPit() yourself if you need a different rate.
    timerInitPit(1000);
}

void timerInitPit(int rate)
{
    // PIT is the Periodic Interval Timer
    
    // PIT is part of system peripherals so no need to enable clock

    // enable and setup the PIT  for specified interval
    AT91C_BASE_PITC->PITC_PIMR = AT91C_PITC_PITEN|AT91C_PITC_PITIEN|(F_CPU/(16*rate)-1);
    // reset the div counter by reading PIVR
    AT91C_BASE_PITC->PITC_PIVR;

    // init global variables
    TimerPauseReg = 0;
    PitCounter = 0;

    // attach interrupt handlers
    processorAicAttachSys(SYSPID_PITC, timerServicePit);
}

void timerAttach(u08 interruptNum, void (*userFunc)(void) )
{
    // make sure the interrupt number is within bounds
    if(interruptNum < TIMER_NUM_INTERRUPTS)
    {
        // set the interrupt function to run
        // the supplied user's function
        TimerIntFunc[interruptNum] = userFunc;
    }
}

void timerPause(int pause)
{
    // wait until [pause] number of pit overflows goes by
    TimerPauseReg = pause;
    while(TimerPauseReg);
}


// interrupt handlers

// This function is the handler for interrupts generated by the PIT
void timerServicePit(void)
{
    // PITC interval interrupt has fired
    // read PIVR (this also clears int flag)
    PitCounter+=AT91C_BASE_PITC->PITC_PIVR>>20;
    
    // decrement the pause register if non-zero
    if(TimerPauseReg)
        TimerPauseReg--;

    // execute user handler if pointer to routine is NOT null.
    if(TimerIntFunc[TIMER_PITOVERFLOW_INT])
        TimerIntFunc[TIMER_PITOVERFLOW_INT]();
}

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