FreqCount for multiple pins

[bgutman]

Hello,
I need to measure the frequency for two pins. I know you can use the FreqMeasureMulti library for multiple pins but FreqMeasure is too slow. Since I am dealing with frequencies of several MHz, I need the FreqCount library. So is there a way to do use FreqCount for multiple pins, similar to the freqmeasuremulti function?

 

[PaulStoffregen]

No, sorry, not really. FreqCount uses LPTMR to do the counting. There's only one of that type of timer in the chip.

 

[bgutman]

Whelp, that's unfortunate. Thanks anyway!

 

[Wozzy]

Do you need the frequency acquisition of all channels to be simultaneous, or can you multiplex the the inputs and alternate the samplings?
With a several MHz input signal, you will only need to sample for a few microseconds to get an accurate reading.

 

[bgutman]

I need simultaneous at a time frame of 10E-8 seconds. A little higher than micros().

 

[Theremingenieur]

I need simultaneous at a time frame of 10E-8 seconds. A little higher than micros().

Two Teensys? Synced by one GPIO pin from the master triggering an interrupt on the slave? Just thinking out loud...

 

[PaulStoffregen]

Hmm... maybe it's theoretically possible on Teensy 3.6 to bring in 2 more clock signals on pins 0 & 1 when configured as ALT4 setting (FTM_CLKIN0 and FTM_CLKIN1). Then those 2 would need to be routed to two of the FTM timers, by bits 24-27 in the SIM_SOPT4 register. Normally the FTM timers clock from F_BUS, by setting bits 4-3 in the FTM*_SC register to 01. But setting those to 11 should let the FTM timer clock from the external signal.

Of course, then someone would have to pretty much write a new version of the library using two of the FTM timers instead of LPTMR.


Edit: Teensy LC and 3.5 might also be able to do this, but Teensy 3.2 definitely can not. Those 2 pins on Teensy 3.2 lack the ALT4 option needed.