Situation: You want to include a timer interrupt service routine in an assembly language program for an AVR-based Arduino. The program will be written, assembled and uploaded using the Arduino IDE.

but instead I found such an thorough and well thought-through answer on StackExchange that I thought I had to point it out. So, t0 the question: What is AVR Arduino interrupt latency? And how can it ...

I wasn't sure where to post this. Sorry if this is not the right place for PlatformIO issues. This minimal sketch hard faults immediately (red LED blinking 4 long / 4 short). #include <Arduino.h> ...