I’ve just released 3.9.10beta1. This has one important change in the IOMCU UART handling. The change stems from a flight log showing a short (under 100ms) stop of VTOL motors in a quadplane during takeoff. The flight went fine, but I think this error is serious enough to warrant a quick release fix.
The IOMCU UART is the serial connection between main micro-controller (called the FMU) and the IO micro-controller (called the IOMCU). That link controls main servo outputs on controllers with separate “main” and “aux” outputs. That UART also carries the state of the safety switch. The error could lead to a brief period where the FMU thinks the safety is engaged when it is not engaged, which is what caused the VTOL motor outputs on the AUX channels to stop.
The error is rare (this is the only time it has been seen), but some ESCs could get in a state where they don’t recover, so even though in this particular flight the issue was benign, I am doing a quick release to fix it.
After this release I plan on starting beta of a 4.0.0 release, which will be based on master and will have a large set of new features. I hope to start that release series in about 10 days time.
The final release of 3.9.10 is now out. Thanks for the test reports!