Other options: FORTH. Icky, but I thought I'd mention it; very fast bringup time . . . but then it's FORTH. A commercial RTOS. There are lots of these, some o

Other options: FORTH. Icky, but I thought I'd mention it; very fast bringup time . . . but then it's FORTH. A commercial RTOS. There are lots of these, some of them are even pretty good. We went the C-and-ASM route and ported over some USB drivers from another in-house OS. Worked okay. USB is horrible to work with, and that was actually the hardest part to get right on our system.