Time elapsed

[LArmstrong1985]

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!

[kerryzhou]

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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