U6 frequency measurement

Be sure that the Pin Offset is set to zero. If you still have problems check out our examples: https://labjack.com/support/software/examples

Timer0 and Timer1 will appear on FIO0 and FIO1 of the U6 if PinOffset=0.

As for frequency measurement ... in general timing individual pulses is best for lower frequencies, whereas counting over time is best for higher frequencies:

https://forums.labjack.com/index.php?showtopic=1105

A great way to measure frequency is by timing individual pulses using Timer mode 2 which is 32-bit Period Measurement:

https://labjack.com/support/datasheets/u6/hardware-description/timers-co...

The U6 has 4 timers, but the total edge rate is limited to 30000 edges per second:

https://labjack.com/support/datasheets/u6/hardware-description/timers-co...

I suggest you test as follows using the test panel in LJControlPanel:

Jumper FIO0 to FIO1 to FIO2.  FIO0 will be a frequency output, FIO1 will be period input, and FIO2 will be a counter input:

TimerClockBase = 48 MHz    (no divisor, so each clock tick is 1/48M => 0.0000000208333 seconds)

#TimersEnabled=2
Timer0:  Mode=PWM16, Value=32768
Timer1:  Mode=RISINGEDGES32

Counter1=Enabled

PinOffset=0    (timers & counters will start at FIO0)

Timer0 will be a 732.42 Hz PWM signal with 50% duty cycle:

https://labjack.com/support/datasheets/u6/hardware-description/timers-co...

Timer1 is measuring the period from rising edge to rising edge.  It is jumpered to Timer0 so the number of clock ticks we will measure is 48000000/732.42 = 65536, which you can see is happening in my attached screenshot.

The test panel in LJCP iterates about once per second, so Counter1 will increment by about 732 counts each time.