At last, live--and counting!
16/03/2026
Eventually the reward: it works!
There are 3 colors for each tiny (the micro-controller board that read the MID pulse counters output):
Every 420s: green or red--red is when a counter change is detected. It's from the second core reporting count changes to the Pi.
Every second: blue. It's the main core idle loop. The main core is dedicated to the ISR recording pulse counts.
Thus the blue flash confirms that the main core handling the ISR is running, and the green/red flash confirms that the second core reporting counts to the Pi is running.