We've just release Copter-3.5.3-rc1 for beta testing.
This means you should be able to download it using the Mission Planner (and perhaps other GCSs too) by selecting Initial Setup >> Install Firmware, then click on the "Beta firmwares" link and the string under the various multicopter and helicopter icons should change to "APM:Copter V3.5.3-rc1".
This is a relatively minor release with just these changes (ReleaseNotes.txt):
- Guided mode support yaw and yaw-rate fields from set-position-target message
- Optical Flow startup retries 10 times
- Bug fixes:
- Septentrio RTK GPS driver robustness improvements for long messages
- dataflash not-logging checks if not initialised
- fix reporting of relative-position-NE-to-home (most users will not notice this difference)
The most serious item is the 1st bug fix which affected the Septentrio RTK GPS driver (it does not affect any other GPSs including the most commonly used UBlox GPSs). One user had their Septentrio GPS configured to output very long messages and experienced a sudden crash after 30minutes of flight. This fix is the result of working with that user to identify and correct the problem. If you're using the Septentrio GPS we highly recommend upgrading to Copter-3.5.3 especially once it's released officially.
All testing of this new release would be great, and please report any issues in this forum. Thanks!
If all goes well with testing we will release it as the official version in about a week.