Above is the picture describing the configuration outside the MCU.
Vin is 0 to 5V Peak to Peak square wave which may have 0 to 50 KHz frequency, or even higher.
The MCU is supposed to handle interrupt every falling OR rising edge(configure as either one of them, but not both) of the /INT port.
In order to not jam the MCU with interrupts in case of very high frequency VIN, I added a simple low frequency filter in front of MCU port.
The problem is that I am seeing false trigger of interrupt, If i set up as rising edge trigger. Everything works fine if i set up interrupt as falling edge.
How I know that Interrupt is false triggering is that I am measuring the time between each interrupts, as I am feeding the certainly known signal(from calibrator, observed with oscilloscope).
The problem goes away if I remove the 10nF capacitor.
However, in my application, I have used up all the timers, so I cannot use timers to limit the interrupt frequency, which forces me to limit it outside of the MCU
The cpu is PIC32 series.
Is there any ways I can achieve purpose of preventing external interrupt from firing too frequently?