FrequencyCount Library

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siavash.esfahani

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Hello All,

Just a quick question about frequencyCount Library. Is it possible to measure frequency above 65MHz with Teensy3.6? If yes, what should I do?


Best regards,

Siavash
 
With that library, no, 65 MHz is the limit.

If you write different code, or edit the library, maybe you can measure higher. Maybe. The main issue is the minimum 1 ms gate time, and overflowing the 16 bit counter. So if you write code for a shorter timing interval to do the measurements (probably the simpler path), or somehow add code to deal with the overflow issues (probably much harder), maybe you could measure higher.

Whether the hardware really would work at higher frequency, and really whether it's truly accurate even this high, is questionable. NXP's datasheet for this chip says on page 18 the maximum clock for LPTMR is 25 MHz.
 
Why not use an external pre-scaler IC? I remember that in the 1980ies, most DIY frequency counter stuff was limited by the speed of available logic ICs and reached normally 10MHz. Using a /64 prescaler IC in ECL logic, one could then go beyond 600MHz.
 
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