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Is there any way in Arduino to set a particular pin(pwm or not) to just generate a square wave out of the desired pin?

For instance, I want to have two pins on my Arduino Uno that output two square waves of 50% duty cycle with different frequencies. But at the same time i want my program to be doing something else. This means that bit-banging two pins in the loop() function just isn't really feasible.

Is there any way I can just set and forget a pin to output a wave?

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    why not analogWrite()? arduino.cc/reference/en/language/functions/analog-io/… – Juraj Apr 11 at 4:27
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    If you don't need more than three different frequencies I highly recommend using the atmega's hardware timers to generate a pwm. In this way you get real parallelism and the main-period will not get delayed. – Sim Son Apr 11 at 16:07
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Setting a pin to output a square wave unattended is exactly what analogWrite does. It just turns on a square wave. If you want a 50% duty cycle then use analogWrite(127) and that will give you a square wave with 50% duty cycle. If you want to alter the frequency then search for altering the frequency of analogWrite, it has been discussed in many many places all over the web.

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What frequencies are you after? You can use blink-without-delay style programming to generate many frequencies. I did that to make this organ-like device with Atmega1284P

https://www.youtube.com/watch?v=4c8idXN4Pg0

It was programmed for 13 notes (full octave), the demo only played CDEFGABC as that was all the switches I had. (13 buttons, 13 outputs, leaving 2 pins for serial and then 4 more free).

The sketch continuously checks to see if a button is pressed, if it is then it checks if enough time has passed to change the output for that note from low to high, or high to low (half-period). While it's waiting for time to pass, other things can be occurring.

If you need higher frequencies, than PWM is the way to go.

About 1/2 way down this page, Nick Gammon explains how to set up the timers for various frequencies.

http://www.gammon.com.au/timers

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