To debug your hardware your might need some insight of the timing on Gpio pins. Or connect some external stuff (remember the Raspi only likes 0..3.3V).
- The program allows to reconstruct the timing (beside from the fastest setting)
- It records even glitches that appear between sampling
- It records a quarter of all samples before triggering
- On a Raspi 4 it allows sample-rates up to ~2MHz