then what could be the best way to do?
Get hold of an oscilloscope or a frequency counter, and tweak your loop times until you get closest to 40kHz.
and amplifier for the square wave?
MAX232 or similar.
then what could be the best way to do?
Get hold of an oscilloscope or a frequency counter, and tweak your loop times until you get closest to 40kHz.
and amplifier for the square wave?
MAX232 or similar.