I have a square wave signal connected to pin D2 (INT0)on Nano. My code fires an interrupt servicing routine when that changes, and is reported within loop(). All this works just fine for every flavour of Nano that I have. In fact, every Arduino that I have … except Nano R4, which is new to me. I can…

I'm not clear about the Resesas core, and what is being configured with attachInterrupt( ) and pinMode( ) but for the R4 pinMode( ) needs to be set before attachInterrupt( ). pinMode(PPS_PIN, INPUT); attachInterrupt(digitalPinToInterrupt(PPS_PIN), EdgeISR, CHANGE); //pinMode(PPS_PIN, INPUT);

[image] cattledog: for the R4 pinMode( ) needs to be set before attachInterrupt( ). Indeed. Results of applying @cattledog 's fix with a 1Hz signal applied to pin 2 of an R4 Nano: 0, 2489903, Starting .........1, 2897898 ..........2, 3397832 ..........1, 3897765 ..........2, 4397700 ........…

Great feedback. Thank you @cattledog for proposing the solution. Thank you @van_der_decken for demonstrating success. “As ever”, the answer was where I wasn’t looking. I say as ever because I feel I should have been looking there, and I wasn’t. I had read that, by default, on startup, the pin is con…

Nano R4 not interrupting?

Official Hardware Nano Family Nano R4

xfpd March 19, 2026, 5:27pm 2

At the bottom of your topic are related topics... This incomplete topic addresses R4 interrupts: How to use Arduino UNO R4 interrupt

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Nano R4 not interrupting?

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