"The remaining chars indicate types of args and must match exactly; these can be preceded by a decimal repeat count: x: pad byte (no data); c:char; b:signed byte; B:unsigned byte; ?: _Bool (requires C99; if not available, char is used instead) h:short; H:unsigned short; i:int; I:unsigned int; (Capital i) l:long; L:unsigned long; f:float; d:double; e:half-float."
Rotor_count is sent from the HD as an unsigned int (U32).