Most of the time you'd want one powerful computer running everything. Danu deliberately does the opposite. She carries three independent brains, and the point of keeping them apart is that no single failure can take down the whole submarine.
Each one has a clearly bounded job:
- The Supervisor is a small, bare-metal microcontroller (an ST Nucleo-F446RE). "Bare-metal" means it runs a single hand-written program with no operating system underneath - nothing to crash, freeze, or get distracted. Its only job is the failsafes: watching for trouble and, if needed, ending the dive, dropping the weights and surfacing Danu. It owns the strobe beacon that helps find her at the surface.
- The Pixhawk 6C is the flight controller - the part that actually steers. It runs ArduSub, the software that reads the sub's motion and drives the thrusters to hold depth and heading. It's a proven, purpose-built piece of hardware, so the risky, real-time job of not tumbling is handled by something reliable and single-minded.
- The Jetson is the AI brain. It plans the mission, runs the cameras, and does the vision work of actually spotting a shipwreck. This is the ambitious, experimental computer - and if its software misbehaves, the other two don't care.
Why the split matters
The Jetson is where new code and heavy AI live, so it's also where bugs are most likely. By law of the design, it cannot override the Supervisor. If the mission software wanders off, the Supervisor is still watching, and the Pixhawk is still "flying". That's the check and balance: the least trustworthy computer has the least authority, and the simplest computer has the last word.
The three talk to each other over a tiny gigabit network switch sized to fit inside Danu's four-inch tube. They cooperate - but each keeps its own counsel.