The explanation for example of delayMicroseconds() is not accurate

[mikecat]

When I executed the example on the reference of delayMicroseconds()(WebArchive)

int outPin = 8;                 // digital pin 8

void setup()
{
  pinMode(outPin, OUTPUT);      // sets the digital pin as output
}

void loop()
{
  digitalWrite(outPin, HIGH);   // sets the pin on
  delayMicroseconds(50);        // pauses for 50 microseconds      
  digitalWrite(outPin, LOW);    // sets the pin off
  delayMicroseconds(50);        // pauses for 50 microseconds      
}

configures pin number 8 to work as an output pin. It sends a train of pulses with 100 microseconds period.

on my Arduino UNO R3 and Arduino 1.0.6, the signal observed on pin 8 was approximately 9207Hz.
It means that the period is approximately 108.6 microseconds, and I think this error is caused due to the execution time of instructions other than delayMicroseconds() (i.e. digitalWrite() and the loop).

From this test, we can say that the sample do not send a train of pulses with 100 microseconds period but sends a train of pulses with approximately 100 microseconds period.
I think this explanation on the reference is a little bit misleading.
The problem becomes bigger when I change the delay from 50 microseconds to 5 microeconds: the output was approximately 55566Hz instead of expected 100kHz.

[mikaelpatel]

@mikecat
Did you try removing the delays? What would you expect then?

[mikecat]

@mikaelpatel
I think it is a tough question to answer, but the result of my test on my Arduino was approximately 115160Hz.

[agdl]

@mikecat I wrote this:

It sends a train of pulses of approximately 100 microseconds period. The approximation is due to execution of the other instructions in the code.

Is it ok for you? If so close the issue please otherwise tell me what you want to add to this page please

[agdl]

@mikecat I'm closing this. Reopen it if needed please