Fitbit Firmware Engineer interview questions

Met the recruiting group at the campus career fair. Later I finished an online coding challenge. A week later I had an HR interview on phone. The HR moved me to the technical interview. But I didn't prepare too much on the operation systems, so I basically failed the last interview.

I met the recruiter at the campus career fair. After that I received a coding challenge link and passed that. A week later I received a call from the recruiter, following by a remote tech interview and a 'take-home exam'. Then I was invited to have an on-site interview. 4 groups, 2 people each.