[bsp][stm32] add rt_hw_us_delay
@@ -86,6 +86,41 @@ void _Error_Handler(char *s, int num)
/* USER CODE END Error_Handler */
}
+/**
+ * This function will delay for some us.
+ *
+ * @param us the delay time of us
+ */
+void rt_hw_us_delay(rt_uint32_t us)
+{
+ rt_uint32_t ticks;
+ rt_uint32_t told, tnow, tcnt = 0;
+ rt_uint32_t reload = SysTick->LOAD;
+
+ ticks = us * reload / (1000000 / RT_TICK_PER_SECOND);
+ told = SysTick->VAL;
+ while (1)
+ {
+ tnow = SysTick->VAL;
+ if (tnow != told)
+ {
+ if (tnow < told)
+ {
+ tcnt += told - tnow;
+ }
+ else
+ {
+ tcnt += reload - tnow + told;
+ }
+ told = tnow;
+ if (tcnt >= ticks)
+ {
+ break;
+ }
+ }
+ }
+}
+
/**
* This function will initial STM32 board.
*/
