LPC1768 / ARM Cortex-M3 microsecond delay

Question

I\'m trying to implement a microsecond delay in a bare metal arm environment( LPC1768 ) / GCC. I\'ve seen the examples that use the SysTimer to generate an interrupt that then d

Answer 1

You can use SYSTICK inside ARM processor for that. Just program it to count each 1uS, or less if you have enough clock speed, and do-while a loop till your delay value expires. Like this:

void WaitUs(int us) {

    unsigned int cnt; 

    while(us-- >0) {
       cnt = STK_VAL; // get systick counter, ticking each 500nS
       while( (STK_VAL-cnt) < 2); // repeat till 2 ticks
    }
}

Bear in mind that this is an example, you'll need to adjust it for counter roll-over among other things.