Timer.c

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#include <stdint.h>     // typedef int8_t, typedef uint16_t, typedef uint32_t
                        // #define UINT32_MAX
#include <stddef.h>     // NULL
#include "SysHwTimer.h" // Hardware timer
#include "Timer.h"      // Prototypes of this module

static const uint32_t MAX_TIMEDIFF = ((UINT32_MAX / 2) - 1);

// for comment see Timer.h
int8_t CheckTimer(uint32_t *pulTimer)
{
    uint32_t ulHwTimer;

    // Timer is inactive:
    if (*pulTimer == 0) return(-1);

    // Get hardware driven timer count:
    ulHwTimer = HwTimerGetValue();

    if (*pulTimer > ulHwTimer)
    {
        if ((*pulTimer - ulHwTimer) < MAX_TIMEDIFF)
        {
            // Timer busy:
            return(1);
        }
        else
        {
            // Timer elapsed:
            *pulTimer = 0;
            return(0);
        }
    }
    else
    {
        if ((ulHwTimer - *pulTimer) >= MAX_TIMEDIFF)
        {
            // Timer busy:
            return(1);
        }
        else
        {
            // Timer elapsed:
            *pulTimer = 0;
            return(0);
        }
    }
}

// for comment see Timer.h
void SetTimer(uint32_t *pulTimer, uint32_t ulValue)
{
    // Convert ulValue from ms to timer tics, round up:
    if (ulValue) ulValue--;
    
    ulValue = (ulValue / TIMER_RESOLUTION_MS) + 1;

    if (ulValue >= MAX_TIMEDIFF) ulValue = MAX_TIMEDIFF - 1;    // sb 2001-9-12

    if (ulValue > 1000)
    {
        ulValue++;
    }

    // Get hardware driven timer value:
    *pulTimer = HwTimerGetValue();

    // Add value (overflow may occure):
    *pulTimer += ulValue;

    // Timer must be greater than 0, since 0 is the reset value for the timer:
    if (*pulTimer == 0) (*pulTimer)++;
}

// for comment see Timer.h
int8_t AddTimer(uint32_t *pulTimer, uint32_t ulValue)
{
    // Check if the timer was initialized
    if ((pulTimer == NULL) || (*pulTimer == 0)) return -1;
    
    // Convert ulValue from ms to timer tics:
    ulValue = ((ulValue - (TIMER_RESOLUTION_MS / 2)) / TIMER_RESOLUTION_MS) + 1;

    // This is not really a sufficiant check...
    if (ulValue >= (MAX_TIMEDIFF / 2)) return -1;

    // Add value (overflow may occure):
    *pulTimer += ulValue;

    // Timer must be greater than 0, since 0 is the reset value for the timer:
    if (*pulTimer == 0) (*pulTimer)++;

    return 0;
}

// for comment see Timer.h
void ResetTimer(uint32_t *pulTimer)
{
    *pulTimer = 0;
}

// for comment see Timer.h
void WaitTimer(uint16_t usValue)
{
    uint32_t ulTimer;

    SetTimer(&ulTimer, (uint32_t) usValue);

    while (CheckTimer(&ulTimer) != 0);
}