Time elapsed

LArmstrong1985 — Tue, 08 May 2018 14:54:07 GMT

I use an LPC11C24, an I want to calculate with accurancy the time elapsed between instruction in my code.

I don't need it only for debug but I need this value in my code. I searched but I haven't found libraries that implement this usual problem. How can I do it? Simple with a timer is right? Do you have sample code or better library for LPC11C24 or similar?

Thank you very much!

Re: Time elapsed

kerryzhou — Fri, 11 May 2018 07:11:52 GMT

Hi Fabio Benevento,

You don't need the lib, it's very simple, just use systick to calculate the code execute time.

Give you an example from other MCU:

    systick_init();
   cal_systick_read_overhead();
   systick_disable();

    systick_init();
   logic_op_demo_with_normalc();
   systick_disable();

uint32_t cnt_start_value;
uint32_t cnt_end_value;
uint32_t overhead;

void systick_init(void)
{
   SYST_CVR = 0x0;   //clear current timer value
    SYST_RVR = 0x00FFFFFF;
    SYST_CSR = SysTick_CSR_CLKSOURCE_MASK | SysTick_CSR_ENABLE_MASK;
}

void systick_disable(void)
{
SYST_CSR &= ~SysTick_CSR_ENABLE_MASK;
}

void cal_systick_read_overhead(void)
{
   uint32_t cnt_start_value;
    uint32_t cnt_end_value;

   cnt_start_value = SYST_CVR;

    cnt_end_value = SYST_CVR;

   overhead = cnt_start_value - cnt_end_value;

#ifdef DEBUG_PRINT
   printf("systick start value: 0x%x\n\r", cnt_start_value);
   printf("systick end value: 0x%x\n\r", cnt_end_value);
   printf("systick current value read overhead: 0x%x\n\r", overhead);
#endif

}

void logic_op_demo_with_normalc(void)
{
    uint32_t cnt_start_value;
    uint32_t cnt_end_value;

   uint32_t execution_cycle;   //actual execution cycle

    //configure PTA5 as GPIO
    PORTA_PCR5 = PORT_PCR_MUX(1);

    //configure PTA5 as output pin
    GPIOA_PDDR |= 0x20;

    cnt_start_value = SYST_CVR;

    GPIOA_PDOR ^= 0x20;

    cnt_end_value = SYST_CVR;

   execution_cycle = cnt_start_value - cnt_end_value - overhead;

#ifdef DEBUG_PRINT
   printf("systick start value: 0x%x\n\r", cnt_start_value);
   printf("systick end value: 0x%x\n\r", cnt_end_value);
   printf("actual execution cycle for logic operation with normal C code: 0x%x\n\r", execution_cycle);
#endif
}

The above example is used to check the GPIOA_PDOR ^= 0x20; execution time.

Wish it helps you!

Have a great day,
Kerry

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