Input capture not detecting square wave

[Qwyntex]

I have built a sine wave to square wave circuit and now want to measure its frequency with the STM. I can see on the oscilloscope that the circuit works, however I can detect neither a rising nor a falling edge with the chip. It is not a problem with the code as I can detect both when they are generated by the chip with PWM or externally with a generator (which is old and its square wave really isn't that square) but also they are much slower.

The frequency of the wave is 1.24MHz, measured with the oscilloscope. I don't think that this is too fast, the timer runs at 96Mhz, but maybe using interrupts at this speed is too much?

The minimum voltage of the wave is 0.6V. I am suspecting that might be too high to be considered a logical 0 but I can't find documentation.

I would appreciate any input and also if you could point me to documentation that would be nice!

 

[tjaekel]

a) if your logic level is not really 3V3 CMOS (where high level is above the limit to see a high, e.g. 2.4V) or the inputs use a Schmitt Trigger (with a hysteresis) - you might not see all pulses properly:
https://learn.sparkfun.com/tutorials/logic-levels/all

b) Nyquist or Shannon Theorem:
    You need 2xFs in order to realize a sine wave (doubled sampling frequency compared to the frequency of the signal)
    for 1.24 MHz sine wave expected (or able to see) - you have to sample (at least) with 2.48 MHz

[Qwyntex]

Using DMA instead of interrupts fixed it. I guess I really shouldn't have used them in the first place.

I am now executing two 'HAL_TIM_IC_Start_DMA' back to back with different variables. I am not entirely certain how they behave when used like that but I think it should start the first one and then immediately start the second one when it finished, like with circular.