I only did the phone interview and did not make it past that. They asked very specific questions about C memory management (static variables, heap, stack, what does the operating system do when it calls a function). In addition they asked about serial interfaces and baud rate and how that translates to characters per second. They also asked about controls, in particular transforms (Laplace in particular) and wanted an in depth review of PID control.

Straight forward - 30 minutes phone screen with behavioral and technical questions on C++. Followed by 5 hour in-person or virtual interview which included both technical and behavioral questions. Each hour was a different interview with different people.