There must be something here that I am assuming, that I shouldn't be.
What test are you doing to show that the yaw channel is not working?
- Is it when you try to fly that it spins like a top?
- Is it when you run the motors before you fly, the yaw stick doesn't change the motors, but the roll stick does?
- Is it that the GCS Input page shows roll slider motion when you move the transmitter roll stick, but the yaw stick doesn't move its GCS slider?
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There are some model templates in the setup wizard that we sometimes call "cloud configs." Some of these may not be well tested and are just what somebody set up and donated. If you are using a cloud config, I suggest that you try running the setup wizard with default settings.
When running the wizard, you have to be careful to move only the one transmitter stick direction that is called for, but that doesn't really sound like the issue. For instance, the throttle channel doesn't have a spring, and it's easy to accidentally move the throttle when trying to just move the yaw.
If you still have the CC3D connected in the way that we got the yaw channel to show up in GCS -> Input -> Receiver Activity
and GCS still shows receiver activity on all 5 radio functions; all on different channel numbers
and you follow all the instructions in the transmitter wizard (you are probably using mode 2) while watching that the moving transmitter cartoon on the GCS has the same transmitter part moving that you are supposed to move in real life
and the end cartoon of the transmitter wizard has all the transmitter functions moving to match what you move in real life
and yaw does nothing to the motors when sitting armed on the ground with the motors idling, but roll does change the motors
Then I am stumped.
If one of the above is not true (this cartoon motion doesn't match that stick motion) then we can go back to that and figure out why.