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Oct 22, 2016, 08:48 AM
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Combined Sbus and PWM output from one receiver?


For reasons I won't get into, I'm building a massive F450 quad. It's for novelty use this halloween and has been interesting to build since my last two quads were 150mm and 70mm.

With this (hopefully) flyable F450, I'm thinking I'll turn it into an AP drone eventually. So I started researching gimbals. I've watched a few Youtube videos and something surprised me.

Obviously, I want to control the gimbal from my Taranis. So I was trying to figure out how the receiver can control both the FC and the gimbal...and it does? A video I saw looked to have the FC controlled using Sbus and then the gimbal controlled directly from the pins of the receiver using PWM.

Receivers can do that? I think the guy in the video used an X8R and connected the Sbus wire to the FC for channels 1-8 and then a dedicated wire from pin 9 for PWM to the gimbal.

Did I see that correctly? He never showed the connections to the FC so I'm not sure how it all worked.
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Oct 22, 2016, 09:48 AM
Registered User
Ace12GA's Avatar
http://www.frsky-rc.com/product/pro.php?pro_id=135

16 channels SBUS / 3 Channels PWM
Oct 22, 2016, 10:12 AM
Physics, or is it fizzix?
flyandride's Avatar
On sbus receivers the pwm outputs are still active. I use tilt servos on the cameras on my quads. When using receivers like the X8R or L9R, I connect the servo directly to the receiver, having assigned one of the sliders to a channel in the Taranis.

Some of my quads have the X4RSB receiver which only has 3 pwm outputs. In that case I enable servo tilt in CF or Betaflight. In the receiver tab, you need to have the flight controller connected and the Taranis on and determine what aux channel the slider controls. And in the motor tab see what servo it controls.

Let's say the motor tab says servo 1. You go to the servo tab and check servo 0 and the aux channel you found in the receiver tab. Servo 2 on the motor tab would be servo 1 on the servo tab. Don't ask me why they made it this way.

Now you've got to go to the unused pwm outputs on the board and figure out which one is outputting the signal. Don't solder a servo to an output until you determine that it's outputting a proper servo signal that you can see is being modulated by your moving the slider. Unused ports are not dead, they put out an idle signal that will burn up a servo if left connected. I use a scope to see the signal. You can use a servo, just touching the signal lead briefly to see if it works.

I've never set it up for 2 channels controlling the camera as I only use tilt. There is supposed to be some way of doing what I have described using channel forwarding. I have never been able to figure out that feature and can't find any documentation on it. There is also a way of self leveling the camera using the servo tilt function. Painless360 on Youtube describes that.

In either connection method I usually have to go to the mixer tab in the Taranis and adjust the weight and offset so the servo is not hitting the stops and buzzing.
Apr 07, 2017, 08:02 AM
Registered User
Hi All,

I created a video showing the differences and setup for Servo Tilt and Channel Forwarding. I hope that somebody can find this useful.

Betaflight Servo Tilt vs. Channel Forwarding (14 min 50 sec)


-Chuck
Apr 07, 2017, 08:29 AM
FA3PR9WM79
Oldgazer's Avatar
I did the same thing for a while with my X9E and an X8R. If you are using a Pixhawk you can setup the AUX outputs to pass through PWM and send that to the gimbal. This is how I control landing gear and a gimbal.


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