exactly what happened to me last job place. I was told very precisely what I'd be working on and actually I based my decision heavily on that. it was some software driver. first day "actually we need you to do something else". I get around low level, os internals stuff, but I'm no electrical engineer to say the least. ended up looking at pcb schematics, debugging hardware and I have while this and drivers go hand in hand, they are radically different worlds. "fine, I'm gonna learn new stuff" thinking too myself. aside from playing with arduino I've never touched hardware and I have no professional interest whatsoever (my interest there ends in watching YouTube videos) and I found it extremely boring and terrible use of my time. things I had to learn could easily be solved by hiring a real electrical engineer. aside from that, it was terrible management and incredibly unsocial, quit after 6 months and apparently the manager quit shortly after because he got another offer... figures.