Timer Code Example

 Hi All!

 I try to understand how to use the timer for LED blinking application. I investigated L138 StarterWare package and found sample application for timer.

 In the code I understood that Timer configured for internal clock used

 TimerConfigure(SOC_TMR_2_REGS, TMR_CFG_64BIT_CLK_INT);

and period time is

#define TMR_PERIOD_LSB32               (0x07FFFFFF)

TimerPeriodSet(SOC_TMR_2_REGS, TMR_TIMER34, TMR_PERIOD_MSB32);

But I don't understood where is setted frequency of internal clock, in other words, what means 0x07FFFFFF in seconds?

 Full code of timer application bellow:

/**
 * \file  timerCounter.c
 *
 * \brief Sample application for timer.
 */

/*
* Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/ 
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*/

#include "uart.h"
#include "hw_uart.h"
#include "interrupt.h"
#include "soc_OMAPL138.h"
#include "hw_syscfg0_OMAPL138.h"
#include "timer.h"
#include "evmOMAPL138.h"
#include "uartStdio.h"

#ifndef _TMS320C6X
#include "cpu.h"
#endif

/******************************************************************************
**                      INTERNAL MACRO DEFINITIONS
*******************************************************************************/
#define STR_LEN                        (13)
#define TMR_PERIOD_LSB32               (0x07FFFFFF)
#define TMR_PERIOD_MSB32               (0x0)

/******************************************************************************
**                      INTERNAL FUNCTION PROTOTYPES
*******************************************************************************/
static void TimerIsr(void);
static void TimerSetUp64Bit(void);
static void TimerIntrSetUp(void);

/******************************************************************************
**                      INTERNAL VARIABLE DEFINITIONS
*******************************************************************************/
static unsigned char cntArr[9] = {'8', '7', '6', '5', '4', '3', '2', '1', '0'};
static volatile unsigned int secCnt = 0;
static volatile unsigned int flagIsrCnt = 0;

/******************************************************************************
**                          FUNCTION DEFINITIONS
*******************************************************************************/
int main(void)
{
    /* Set up the UART2 peripheral */
    UARTStdioInit();

    /* Set up the Timer2 peripheral */
    TimerSetUp64Bit();

    /* Set up the AINTC to generate Timer2 interrupts */
    TimerIntrSetUp();

    /* Enable the timer interrupt */
    TimerIntEnable(SOC_TMR_2_REGS, TMR_INT_TMR12_NON_CAPT_MODE);

#ifndef _TMS320C6X
    /* Switch to non privileged mode; This is done for demonstration purpose */
    CPUSwitchToUserMode();
#endif

    /* Send the first String */
    UARTPuts("Tencounter: 9", -1);

    /* Start the timer. Characters from cntArr will be sent from the ISR */
    TimerEnable(SOC_TMR_2_REGS, TMR_TIMER12, TMR_ENABLE_CONT);

    /* make sure all the characters from cntArray from ISR */
    while(secCnt < 9)
    {
        /* Replace previous number each time the timer interrupt occurs */
        if(flagIsrCnt)
        {
            UARTPutc('\b');
            UARTPutc(cntArr[secCnt]);
            secCnt++;
            flagIsrCnt = 0;
        }
    }

    /* Disable the timer. No more timer interrupts */
    TimerDisable(SOC_TMR_2_REGS, TMR_TIMER12);

    /* Halt the program */
    while(1);
}

/*
** Timer Interrupt Service Routine
*/
static void TimerIsr(void)
{
    /* Disable the timer interrupt */
    TimerIntDisable(SOC_TMR_2_REGS, TMR_INT_TMR12_NON_CAPT_MODE);

#ifdef _TMS320C6X
    /* Clear interrupt status in DSPINTC */
    IntEventClear(SYS_INT_T64P2_TINTALL);
#else
    /* Clear the interrupt status in AINTC */
    IntSystemStatusClear(SYS_INT_TIMR2_ALL);
#endif
    TimerIntStatusClear(SOC_TMR_2_REGS, TMR_INT_TMR12_NON_CAPT_MODE);

    /* Signal application to print a new character */
    flagIsrCnt = 1;
  
    /* Enable the timer interrupt */
    TimerIntEnable(SOC_TMR_2_REGS, TMR_INT_TMR12_NON_CAPT_MODE);
}


/*
** Setup the timer for 64 bit mode
*/
static void TimerSetUp64Bit(void)
{
    /* Configuration of Timer */
    TimerConfigure(SOC_TMR_2_REGS, TMR_CFG_64BIT_CLK_INT);

    /* Set the 64 bit timer period */
    TimerPeriodSet(SOC_TMR_2_REGS, TMR_TIMER12, TMR_PERIOD_LSB32);
    TimerPeriodSet(SOC_TMR_2_REGS, TMR_TIMER34, TMR_PERIOD_MSB32);
}

/*
** Set up the ARM Interrupt Controller for generating timer interrupt
*/
static void TimerIntrSetUp(void)
{
#ifdef _TMS320C6X
    /* Initialize the DSPINTC */
    IntDSPINTCInit();

    /* Register the Timer ISR */
    IntRegister(C674X_MASK_INT4, TimerIsr);

    /* Map Timer interrupts to DSP maskable interrupt */
    IntEventMap(C674X_MASK_INT4, SYS_INT_T64P2_TINTALL);

    /* Enable DSP interrupt in DSPINTC */
    IntEnable(C674X_MASK_INT4);

    /* Enable DSP interrupts */
    IntGlobalEnable();
#else
    /* Initialize AINTC and register timer interrupt */
    IntAINTCInit();
    
    /* Register the Timer ISR */
    IntRegister(SYS_INT_TIMR2_ALL, TimerIsr);
  
    /* Set the channel number for Timer interrupt, it will map to IRQ */
    IntChannelSet(SYS_INT_TIMR2_ALL, 2);
   
    /* Enable IRQ for ARM (in CPSR)*/
    IntMasterIRQEnable();
  
    /* Enable AINTC interrupts in GER */
    IntGlobalEnable();

    /* Enable IRQ in AINTC */
    IntIRQEnable();

    /* Enable timer interrupts in AINTC */
    IntSystemEnable(SYS_INT_TIMR2_ALL);
#endif
}
/***************************** End Of File ***********************************/