Hi,
Is it possible to use the analog comparator and interrupt/timer to measure the frequency of a square wave with 500mvpp, without amplifying.
The program I wrote works for any signal with 2vpp. I tried to use a 0.3v ref signal to ANI0( Digital pin 6) and measure the 500mvpp on ANI1( Digital pin 7). But it's still not working. Is it because of any voltage limits on the ports.
Does your square wave have any DC offset?
No, it does not.
I haven't use it, by I remember reading an article by Nick Gammon explaining how to use the analog comparator to generate an interrupt when the input passes a threshold. If you can get that working and use if to detect the high/low transitions then you could use conventional timing techniques to determine the frequency. This would take more code than just polling the input with analogRead(), but would give you a much faster solution which would work at higher frequencies. (I don't know whether it would be necessary or sufficient to cope with your target frequency range, because you haven't said what that is.)
I'm apologize for providing less information. I'm actually following this tutorial Measuring Signal Frequency with Arduino – Fiz-ix. It works well for signal with 2vpp signals. I modified it to use my own reference voltage ACSR = ACSR | B00000010 on AN01, and supplied 0.3v volt, so that I thought It could detect the 0.5v raise. However, it does not seem to work.
I'm looking forward to measure frequencies ranging 5khz - 100khz.