Sadly the library doesn't work on the Arduino Pro Mini 3.3 V, 8 MHz (ATmega 328P) variant.

It works fine on an Arduino Uno 16 MHz, and it works on the Arduino Pro Mini 8 MHz as well if I set the the processor version to 5 V, 16 MHz in the IDE, but of course then the timings are not correct... Tried it on multiple boards.

I'm guessing something might be wrong with prescaler selection or 'us' calculation from the 'f_cpu' variable but I'm not sure.

Kind regards,
Benjamin