I wanted to write about this one because they have some decent artistry to the hiring process and look like they are pretty collaborative -- hence, a good place to learn.
They have a simple coding exercise to do along with the application. The subsequent phone screen involved discussion of C++, RTOSes and how they work, mutexes, and Synapse culture. The inevitable coding question on collabedit.com was a simple one in C about linked lists, then discussion afterwards. All of this was a fun discussion and the interviewer answered many questions I had, including the general kind of projects he works on.
I went in for the full-loop, which consisted of three phases, one with a senior engineer at or near management level and in any case with long experience in computing. The interview involved about one third discussion of my work and projects, a third coding on the whiteboard, with a basic data structures question, then adding a requirement beyond the basics to see how I'd handle that, and then the final third addressing my concerns about their recent layoff rounds and balance of working independently and working together. The second overall phase was technical discussion with two engineers about a range of topics including testing, memory management, and general environments they address in their work. Finally the third round consisted of structurally non-technical discussion with three engineers (not strictly software engineers); basically, let's shoot the breeze and see if we can get along and let's see how the candidate thinks and presents himself.
I very much liked that they had a large component of the process devoted to figuring out whether the candidate is a good fit for their team in the more "intangible" aspects.
Overall, I enjoyed the Synapse interview process, and I would guess that their process yields a large pool of qualified final candidates from which they pick in the end (rather than a very small pool of extremely nitpicked candidates). I liked that they didn't seem fixated on any particular technology. That being said, it's possible that I didn't impress them enough with Cortex M experience -- as the interviews went well from my perspective, perhaps something else beyond my perception wasn't a good fit or they just had a pretty sweet pool to pick from. The whole process was 3.5 weeks from application to "no".