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[F767ZI] Determining Frequency of an analog Signal with digital Input Pins

Question asked by Armin L. on Feb 16, 2018
Latest reply on Feb 16, 2018 by AvaTar



On the NUCLEO-F767ZI I want to extract information from an analog signal that is frequency-modulated. The frequency range is 100...500 kHz. The signal is not quadrature, but sinusoidal with an amplitude of 5 V. I thought about feeding this signal to a digital input pin (five-volt tolerant) and creating an interrupt as soon as the input changes from LOW to HIGH (>= 3.3 V). In this interrupt I copy the clock cycle counter of a timer that is afterwards reset to count up from zero again... until the next change from LOW to HIGH occurs on the input pin.
Would that be a possible approach? I know that I have to somehow block the negative half-cycle of the sinusoidal voltage in order not to destroy the GPIO.
Are there other concerns I did not think about yet? Any hints or recommendations from you?
I do not want to use the ADCs because they only provide 2.4 MSPS which is a quite poor resolution regarding the frequency of the analog signal.


Thanks in advance!