- cmake NuttX build wrapper compile in place instead of copying source tree to build directory
- slightly faster skipping necessary copying (depending on system)
- allows debugging in place
- easier to work directly in NuttX following official documentation
- simplifies overall build which should make it easier to resolve any remaining NuttX dependency issues in the build system
- the downside is switching back and forth between different builds always require rebuilding NuttX, but I think this is worth the improved developer experience
- also no longer builds px4io and bootloader in every single build, for most users these rarely change and we're wasting a lot of build time
- no longer start sercon or mavlink usb by default
- on USB connection (VBUS) monitor serial USB at low rate and start Mavlink if there's a HEARTBEAT or nshterm on 3 consecutive carriage returns
- the mavlink USB instance is automatically stopped and serdis executed if USB is disconnected
- skipping Mavlink USB (and sercon) saves a considerable amount of memory on older boards
- same pattern as other new drivers (state machine, checked register mechanism, no sleeps, etc)
- self test has been rolled into regular startup sequence
- still I2C only, but will be expanded in the future
- configure to high accuracy preset
- currently the main change is that it reduces the max number of ORB multi instances to 4, but usage will be expanded as needed
- limits number of EKF2 multi instances to 2.
- enabled on all cortex m4 boards
- simple state machine to reset, configure, etc
- checked register mechanism (sensor will reset itself on configuration error)
- configured in 16 bit mode (1320 LSB/Gauss instead of 330 LSB/Gauss)
- adjusted orientation handling in driver to match datasheet as closely as possible
- in many external compass units the rotation was wrong and very difficult to actual determine how to set correctly
- always check with state machine before reboot/shutdown
- respect BOARD_HAS_POWER_CONTROL (shutdown from command, low battery, power button)
- px4_shutdown_request add optional delay and always execute from HPWORK
- px4_shutdown_request split out px4_reboot_request