120 khz with arduino

How do i generate a 120 khz square wave frequency using arduino. Please help i know that there is someway to do this in software.

Please help i know that there is someway to do this in software.

in software means that you don't want to use the hardware timers?

Have a look at http://arduino.cc/en/Reference/DelayMicroseconds replace the value 50 in the two lines delayMicroseconds(50); by a value that fits your needs, e.g.: delayMicroseconds(1); and measure the frequency on the output pin... modify the value until you read 120kHz. On my Arduino I can't get better than 108kHz with this software solution.

Maybe you consider using a hardware timer (e.g. timer1) for your problem?

Ya, is their any delay that is smaller than "delaymicroseconds"?

There is no function that waits shorter than microseconds, sorry.

But you can wait with
asm volatile(“nop”);

and with my Arduino Diecimila (atmega168 at 16MHz)
the following code is gets very close to 120kHz:

uint8_t outPin = 2;

void setup()
{
  pinMode(outPin, OUTPUT);
  digitalWrite(outPin, LOW);
}

void loop()
{
  digitalWrite(outPin, HIGH);   // sets the pin on
  asm volatile("nop");
  asm volatile("nop");
  asm volatile("nop");
  asm volatile("nop");
  asm volatile("nop");
  asm volatile("nop");
  asm volatile("nop");
  digitalWrite(outPin, LOW);    // sets the pin off
  asm volatile("nop");
  asm volatile("nop");
  asm volatile("nop");
  asm volatile("nop");
  asm volatile("nop");
  asm volatile("nop");
  asm volatile("nop");
}

maybe on your hardware you must try more or less of the nop expressions… and I do not recommend this solution. A timer would be the better choice, but you asked for a software solution.

Oh and your Arduino should do nothing else while he is running this code… why do you need this 120kHz?

Great, Thanks for the code it works perfectly. Is this a square wave frquency? One other question, how to i turn this output into dc, into ac power with a dc source, arduino.

how to i turn this output, dc, into ac power with a dc source, which is arduino.**** sorry for the misinterpretation...