stm32 168MHz delay

gistfile1.txt

/* 168MHz = each clock cycle is 6ns. Loop is always 6 clock cycles?
 * These can get clock stretched if we have interrupts in the background.
 */
void delay_ms(const uint16_t ms)
{
  uint32_t i = ms * 27778;
  while (i-- > 0) {
    asm("nop");
  }
}

void delay_us(const uint16_t us)
{
  uint32_t i = us * 28;
  while (i-- > 0) {
    asm("nop");
  }
}


/* every delay 100ns at stm32 168Mhz */ 
static const uint32_t g_unNSDelayTicks[10] = {1,4,9,15,21,27,32,38,43,49}; 
static inline void delay_100ns(uint32_t ns100_n) {
	  int r0;
		uint32_t ns100 = g_unNSDelayTicks[ns100_n];
    __ASM volatile ("mov r0, ns100 \n"
		    "loop100us: subs r0, #1 \n"
	      " bhi loop100us \n");
}