Creating Square Waves with Programmable Frequencies?

Using Arduino Programming Questions
9

Ok, after a little testing, it seems the original frequency can range from about 5Hz to as fast as about 300Hz. The idea is measure that frequency, adjust it a bit based on the setting of a trim pot, and create an adjusted frequency to output. With that as the goal, please comment on this as an approach:

//measures timing of square wave on pin 20 (interrupt 3)
//adjustes that speed based on setting of pot on pin A0
//creates a square wave with adjusted frequency on pin 21

volatile int adjustedFreq;  
volatile int latestSpeed;
volatile int lastSpeed;
unsigned long startTime;
unsigned long now;
int speedoPin =21;


void setup() {
  pinMode(speedoPin, OUTPUT);
  attachInterrupt(3, iSr, CHANGE);}
 
 
void loop()
//creates square 
{
  startTime=micros(); now=startTime;
  while (now-startTime<adjustedFreq) {speedoPin=HIGH; now=micros();}
  startTime=micros(); now=startTime;
  while (now-startTime<adjustedFreq) {speedoPin=LOW; now=micros();}
} 
  
void iSr()
//calculates length of most recent pulse and adjusts it based on pot setting on A0
{
  latestSpeed=micros();
  adjustedFreq=(latestSpeed-lastSpeed)*(analogRead(A0)/512);  
  lastSpeed=latestSpeed;
}

Moderator edit:
</mark> <mark>[code]</mark> <mark>

</mark> <mark>[/code]</mark> <mark>
tags added.