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FPV Video Switcher Switching

(Matt) #1

Hi guys

I have successfully got 3 analogue cameras working via FPV video switcher. I had to place RC filters on each line to clean the image up but now the images are nice and sharp.
Im having an annoying time with the switching of the channels. The switcher can use PPM and PWM from a RC Receiver.
Basically if you took the full range of a servo and split into 3 sectors, as the “position” of the servo goes through each sector it selects the camera in that sector, if that makes sense. Designed for use with a 3 position toggle switch on an RC remote.

Using a PWM channel out to switch is creating problems, im guessing due to servo frequency being way to high. It is switching the cameras but getting major glitching on the image. (Anyone have any other suggestions?) I’m having success using a relay channel however i have to time my on/off presses to create the “illusion” of a PWM signal and its frustrating and spiratic.

My ideal scenario is to just toggle a relay channel and have each camera switch in sequence. Can this be done via a Mavlink script possibly?
Or any other suggestions on parameters that can be changed to help this scenario out?

Im Fully open to ideas on how to tweak this please.
Thanks heaps

(Matt) #2

Sorry should have clarified a few more items:

When using Aux 1 - Servo 1 to try the PWM switching. Cameras did switch but i was getting a very glitchy screen and i have to wait for the servo output to change in order to see the cameras change.

When using Aux 5 - Relay 1 to pulse on/off i get a solid image and switching but the action of timing the on / off myself is tricky to get exactly right and not practical for ROV operations.

Im after a solution to be able to switch using just a single relay channel (Aux 5 maybe?) OR if someone can think of a solution why the Servo 1 channel is causing glitching (frequency to high maybe?) that would be awesome.

Despite my hunts through the manuals im still not 100% on the characteristics of each of the channel types. Can anyone point me to where that information is? Perhaps i can work something out that way.

(Anthony White) #3

Hi Mat -

Nice find on the video switcher that is controlled by servo PWM ! When trying to use the aux channels to actuate things like servos, lumens, or whatever, it can be quite helpful to look within QGC to see what the pixhawk thinks it’s outputting on the channel you’re interested in. You can do this via widgets/mavlink inspector, and find the aux channel. The number will be in microseconds, signifying the pulse length varying from 1000 to 2000, with 1500 at center. If you verify the channel you’re connected to is changing when you toggle it with linked joystick buttons, and the video board still isn’t responding I’d try playing around with the max/min pwm values under parameters. Maybe the board expects a broader or narrower range for the signal pulse.

Checkout the documentation for details on this.

Happy hunting!


(Jacob) #4

If the switcher is pwm controlled, then using the relay options is not the right way, and you will not be able to get it consistent with that route.

You should use the pwm. Unfortunately, the aux channel outputs are not available via mavlink like Tony suggested checking. You could try to map it to one of the main outputs, and adjusting the pwm frequency.
The pwm frequency on the aux outputs is always 50Hz.

You can also invest in alogic analyzer, they’re awesome for troubleshooting stuff like this.