// In case of using LGT MCU need one more NOP instuction to compensate shorter executiom time.
#if defined(__LGT8F__)
  #define _ONENOP_ " nop \n\t"
#else
  #define _ONENOP_ ""	
#endif

#define _MORENOP_ ""

/* Delay for the given number of microseconds.  Assumes a 1, 8, 12, 16, 20 or 24 MHz clock. */
void delayMicroseconds(unsigned int us)
{
	// call = 4 cycles + 2 to 4 cycles to init us(2 for constant delay, 4 for variable)

	// calling avrlib's delay_us() function with low values (e.g. 1 or
	// 2 microseconds) gives delays longer than desired.
	//delay_us(us);
#if F_CPU >= 32000000L
	// for the 32 MHz clock on most Arduino boards

	// The overhead of the function call takes 14 (16) cycles,
    //	which is half microsecond

	// zero delay fix
	if (!us) return; //  = 3 cycles, (4 when true)

	// the following loop takes 1/4 of a microsecond (8 cycles)
	// per iteration, so execute it four times for each microsecond of
	// delay requested.
	us <<= 2; // x4 us, = 4 cycles
	
	// 32 MHz is two times faster than 16 MHz so need more nop in the
	// wait cycle for to keep the possible longest delay capability
#undef  _MORENOP_
#define _MORENOP_ " nop \n\t  nop \n\t  nop \n\t  nop \n\t"

	// account for the time taken in the preceeding commands.
	// we just burned 19 (21) cycles above, remove 3, (3*8=24)
	// us is at least 4 so we can substract 3
	us -= 3; // = 2 cycles,

#elif F_CPU >= 24000000L
	// for the 24 MHz clock for the aventurous ones, trying to overclock

	// zero delay fix
	if (!us) return; //  = 3 cycles, (4 when true)

	// the following loop takes a 1/6 of a microsecond (4 cycles)
	// per iteration, so execute it six times for each microsecond of
	// delay requested.
	us *= 6; // x6 us, = 7 cycles

	// account for the time taken in the preceeding commands.
	// we just burned 22 (24) cycles above, remove 5, (5*4=20)
	// us is at least 6 so we can substract 5
	us -= 5; //=2 cycles

#elif F_CPU >= 20000000L
	// for the 20 MHz clock on rare Arduino boards

	// for a one-microsecond delay, simply return.  the overhead
	// of the function call takes 18 (20) cycles, which is 1us
	__asm__ __volatile__ (
		"nop" "\n\t"
		"nop" "\n\t"
		"nop" "\n\t"
		"nop"); //just waiting 4 cycles
	if (us <= 1) return; //  = 3 cycles, (4 when true)

	// the following loop takes a 1/5 of a microsecond (4 cycles)
	// per iteration, so execute it five times for each microsecond of
	// delay requested.
	us = (us << 2) + us; // x5 us, = 7 cycles

	// account for the time taken in the preceeding commands.
	// we just burned 26 (28) cycles above, remove 7, (7*4=28)
	// us is at least 10 so we can substract 7
	us -= 7; // 2 cycles

#elif F_CPU >= 16000000L
	// for the 16 MHz clock on most Arduino boards

	// for a one-microsecond delay, simply return.  the overhead
	// of the function call takes 14 (16) cycles, which is 1us
	if (us <= 1) return; //  = 3 cycles, (4 when true)

	// the following loop takes 1/4 of a microsecond (4 cycles)
	// per iteration, so execute it four times for each microsecond of
	// delay requested.
	us <<= 2; // x4 us, = 4 cycles

	// account for the time taken in the preceeding commands.
	// we just burned 19 (21) cycles above, remove 5, (5*4=20)
	// us is at least 8 so we can substract 5
	us -= 5; // = 2 cycles,

#elif F_CPU >= 12000000L
	// for the 12 MHz clock if somebody is working with USB

	// for a 1 microsecond delay, simply return.  the overhead
	// of the function call takes 14 (16) cycles, which is 1.5us
	if (us <= 1) return; //  = 3 cycles, (4 when true)

	// the following loop takes 1/3 of a microsecond (4 cycles)
	// per iteration, so execute it three times for each microsecond of
	// delay requested.
	us = (us << 1) + us; // x3 us, = 5 cycles

	// account for the time taken in the preceeding commands.
	// we just burned 20 (22) cycles above, remove 5, (5*4=20)
	// us is at least 6 so we can substract 5
	us -= 5; //2 cycles

#elif F_CPU >= 8000000L
	// for the 8 MHz internal clock

	// for a 1 and 2 microsecond delay, simply return.  the overhead
	// of the function call takes 14 (16) cycles, which is 2us
	if (us <= 2) return; //  = 3 cycles, (4 when true)

	// the following loop takes 1/2 of a microsecond (4 cycles)
	// per iteration, so execute it twice for each microsecond of
	// delay requested.
	us <<= 1; //x2 us, = 2 cycles

	// account for the time taken in the preceeding commands.
	// we just burned 17 (19) cycles above, remove 4, (4*4=16)
	// us is at least 6 so we can substract 4
	us -= 4; // = 2 cycles

#else
	// for the 1 MHz internal clock (default settings for common Atmega microcontrollers)

	// the overhead of the function calls is 14 (16) cycles
	if (us <= 16) return; //= 3 cycles, (4 when true)
	if (us <= 25) return; //= 3 cycles, (4 when true), (must be at least 25 if we want to substract 22)

	// compensate for the time taken by the preceeding and next commands (about 22 cycles)
	us -= 22; // = 2 cycles
	// the following loop takes 4 microseconds (4 cycles)
	// per iteration, so execute it us/4 times
	// us is at least 4, divided by 4 gives us 1 (no zero delay bug)
	us >>= 2; // us div 4, = 4 cycles
	

#endif

	// busy wait
	__asm__ __volatile__ (
		"1: sbiw %0,1" "\n\t" // 2 cycles in Atmel AVR or 1 cycle in LGT MCU
		_ONENOP_
		_MORENOP_
		"brne 1b" : "=w" (us) : "0" (us) // 2 cycles
	);
	// return = 4 cycles
}