Falling edge capture mode on the ATMEGA328

#1 · June 23, 2026, 10:07 pm

'm having trouble getting the capture mode to work on the falling edge. Even setting the ICSE1 bit to 0, it only works on the rising edge.

#2 · June 24, 2026, 9:05 am

Hi.

Input Capture Unit in Atmega328 is working for me at both edges.
Can you share circuit and firmware to reproduce the issue?

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#3 · June 24, 2026, 11:08 am

I observe the capture of TCNT1 to ICR1 in MCU MONITOR and, even changing the value of the ICSE1 bit, the capture only happens on the rising edge.

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#4 · June 24, 2026, 12:45 pm

Thank you for the files.

Your code works for me in rising or falling edge.
But I have to use a pullup resistor on PB0:

sbi PORTB,0             ; pulup do pino PB0

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