Radio glitches with SBus (NuttX)

Did a flight with master two days ago and was surprised by an unexpected RTL. The seems to contain radio glitches going down to PWM zero on random channels.

My radio hardware:

  • TBS Crossfire TX module on FrSky X10S
  • TBS Crossfire Micro Rx, via S-Bus and Mavlink (both)
  • Pixhawk 1 (original 3DR) on NuttX (not ChibiOS this time!)

The general radio setup with Crossfire (including mechnical/antenna setup) is proven with hundreds of hours of air time during the last two years and is expected to give a decent range of at least 500m (but some components are new). The whole flight was in close proximity, so a real failsafe situation is highly unlikely (but off course, not impossible).


I had the same yesterday. Pixhawk 1, Copter 3.5.7 and Taranis X9D with X8R receiver. CH5 glitched to 2100 and the day before I had CH6 going to 1830

What firmware? Please test with current master.

it was 3.5.7. I have been flying with this release for a long time now. Can it be due to the firmware? I was thinking more of a defective receiver. I am sending 16 channels, with failsafe set to custom with CH3 (throttle) set to None and the other channels (except 1 to 3) to hold.

I’d missed that this was nuttx.
There was recently an rc input rework in ChibiOS builds.
Could still be relevant though: I’m not sure whether the iomcu firmware for 3.5.7 was nuttx or ChibiOS. Worth checking perhaps.
Could be hardware though

I was on nuttx. I’m sure of that

As a side point, to be clear to others reading this thread, in general we don’t recommend flying with master. A bench test is OK if we think we may have resolved the issue in master but I definitely don’t recommend flying with master because it hasn’t undergone the testing that’s gone into beta or stable releases.

Yes. Sorry for not being clearer.