1 /* 2 * Copyright (c) 2023 Juan Manuel Cruz <jcruz@fi.uba.ar> <jcruz@frba.utn.edu.ar>. 3 * 4 * See file `LICENSE` for full details 5 */ 6 7 #include "main.h" 8 9 /* blocking delay in microseconds using the SysTick timer */ 10 void systick_delay_us(uint32_t delay_us) 11 { 12 uint32_t start, current, target, elapsed; 13 14 if (0 == delay_us) 15 return; 16 17 /* Get the start value of the SysTick counter */ 18 start = SysTick->VAL; 19 20 /* Calculate the total number of SysTick counts required for the delay */ 21 target = delay_us * (SystemCoreClock / 1000000UL); 22 23 /* Loop until the required counts have elapsed */ 24 while (1) 25 { 26 /* Get the current value of the SysTick counter */ 27 current = SysTick->VAL; 28 29 /* Handle the case where the SysTick counter wraps around, */ 30 /* counts down to 0 and reloads */ 31 if (current <= start) 32 { 33 elapsed = start - current; 34 } 35 else 36 { 37 /* Counter wrapped around, */ 38 /* add the reload value to account for the wrap */ 39 elapsed = SysTick->LOAD + start - current; 40 } 41 42 /* Exit the loop when the desired delay is reached */ 43 if (elapsed >= target) 44 { 45 break; 46 } 47 } 48 }
