// Writing a custom delay-loop routine and timing how fast it is.


// delay for amount of time specified by loops (no-op loop)
inline void fine_time(uint32_t loops)
{
    for (uint32_t fine_loops=loops; fine_loops>0; fine_loops--) 
    {   asm("nop");
    }
}


void time_loops(uint32_t inner_loops)
{
    uint32_t outer_loops = 1;	// number of times to repeat fine_tune call
    for (uint32_t scaled_inner=inner_loops; scaled_inner< (1<<24); scaled_inner*=2)
    {    outer_loops *=2;
    }
    
    uint32_t start_time=micros();		// start time (usec)
    for (uint32_t loops=outer_loops; loops>0; loops--)
    {    fine_time(inner_loops);
    }
    uint32_t time = micros() - start_time;	// elapsed time (usec)
    
    Serial.print(outer_loops);
    Serial.print(" outer ");
    Serial.print(inner_loops);
    Serial.print(" loops ");
    Serial.print( time);
    Serial.println(" usec");

}

void setup(void)
{
    Serial.begin(115200);
}

void loop(void)
{
//    time_loops(0);  // BUG: this asks for a delay of 2^32  
    time_loops(1);	// This is the shortest requestable delay
    
    for (uint32_t iters=2; iters<= (1<<27); iters=2*iters)
    {    time_loops(iters);
    }
}