Measuring input signal frequency is a common requirement in many applications like tachometer, frequency meter, tone detection, etc. The two classic approaches of frequency measurement are measure the number of cycles in a fixed period of time and measure the time of one cycle. This application note from Cypress discusses the advantages and limitations of these methods and also presents a hybrid approach along with a sample project enabling measurement of frequencies with a typical error of 0.0016% (16 ppm).
Frequency measurement demo