Decisions (ADR)

Each Architecture Decision Record explains one choice that shapes the code: the context, what was decided, what it costs, and what was rejected. The records are short and are not rewritten. When a decision changes, a new record replaces the old one, and the old one is marked Superseded.

ADR	Decision	Status
0001	Attitude: invariant EKF on SO(3)	Accepted
0002	Multi-rate estimation pipeline driven by the IMU FIFO	Accepted
0003	The flight core runs in the ImuTask, isolated from BLE	Accepted
0004	Altitude: a linear Kalman filter in cascade on the attitude	Accepted
0005	Portable drivers/ separate from board-specific bsp/	Accepted
0006	A bridge MCU for the PMW3901, firmware on registers	Accepted
0007	Battery monitor in its own task, decisions in the flight core	Accepted
0008	Flight log as a sector ring, downloaded over USB CDC	Accepted
0009	USB is a ground link: no flight commands, no arming while connected	Accepted

New record. Copy the template below to NNNN-short-title.md, add it to this table and to nav in mkdocs.yml.

# NNNN. Title

- **Status:** Proposed | Accepted | Superseded by NNNN
- **Date:** YYYY-MM-DD

## Context
## Decision
## Consequences
## Alternatives considered