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Using AUX pins as relays for CHDK

Posted by Dave Williams on February 11, 2014 at 12:39pm

I'm confused and a bit frustrated, would appreciate any help as I'm not sure how to proceed.

Setup: I have a pixhawk autopilot running Arduplane 2.77, using Mission Planner 1.2.95

I've been following this guide to get my CHDK enabled camera working with my pixhawk. I'm interested in getting the camera triggering based on distance traveled.

Obviously the guide was written with APM in mind, so it needs to be adapted a bit for pixhawk; specifically the setting for RELAY_PIN. I've kept the rest of the settings the same as in the tutorial.

Pixhawk has 6 AUX ports according to the quick start guide, I am assuming that the numbers above the pins correspond to the AUX port numbering. When you mouse over the RELAY_PIN parameter, it says that pin 54 corresponds to Pixhawk FMU AUX1.

Tried setting RELAY_PIN to 54, no joy. Did a bit more looking, discovered in the release notes for 2.77: 

"Improved relay code
The relay and servo set code has had a major overhaul, with up to 4 relays now supported for MAVLink control and much better support for the DO_SET_SERVO, DO_SET_RELAY, DO_REPEAT_SERVO and DO_REPEAT_RELAY MAVLink commands. Along with these changes is a new parameter BRD_PWM_COUNT which allows you to specify how many auxillary PWM outputs to enable, with the remaining outputs being available as digital relays. This allows you to re-assign some of the aux servo outputs on Pixhawk for use as relays, by setting the RELAY_PIN, RELAY_PIN2, RELAY_PIN3 and RELAY_PIN4 parameters. The pin numbers for these pins start at 50 for the first aux servo pin, and go to 55 on Pixhawk."

Additionally,I found this github issue about this same problem that states that the Pixhawk can't trigger CHDK because its relay pins operate at 3.3V instead of 5V.

So i suppose my specific questions are:

1) Is AUX1 pin 50 or 54?

2) Can anyone confirm that the relays, when working properly, won't be able to trigger CHDK?

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Replies

    • Steve Pharis > iskess August 3, 2014 at 8:27am

      Servo activation just doesn't work.  Same issue as many others have reported - the pulse bounces between 0 and 10-11 according to chdk.  Whether through passthrough or servo on any channel, the trigger will not fire using the methods in this thread.  I think a better route might be to get an actual relay and just run a basic remote script.  Relay works just fine on any AUX channels, but in plane, I do not see a method to take control of that manually - only distance or mission trigger.

      • iskess > Steve Pharis August 3, 2014 at 11:36am
        Sorry, I'm using a PWM (servo) based shutter trigger. I use the one from Flytron, it's similar to the Genwire. If you are using the relay method you will need an LED switch. Check out Duffy's tutorial: http://flightriot.com/remote-sensing/trigger/
        Flightriot.com
        • Steve Pharis > iskess August 3, 2014 at 3:31pm
          I'm moving that way. I have a PWM based switch on the way. $6 is way cheaper than my time messing with this.
          • Martin Poller > Steve Pharis September 10, 2014 at 2:34pm

            @Steve, can you explain more about how you have it working on APM Plane, triggering by distance on the servo outputs Aux 1-6, are you using a Cannon with CHDK, and are you using a usb cable like the Gentwire thanks Martin.

            • GocGoc > Martin Poller September 11, 2014 at 3:45am

              Does anyone have the camera triggering using a pixhawk on plane?  I have it successfully working on copter using the pixhawk.  Is plane any different?

              • Steve Pharis > GocGoc September 11, 2014 at 12:39pm

                @Martin

                I ended up using a turnigy PWM switch on AUX1.  I set AUX1 in parameters to be the camera trigger.  Once you do that, you can tie the trigger to be distance based, or TX switch based.  I am using a Cannon with CHDK and the default script (which will fire the shutter when it gets voltage).  I am using a USB cable with the 5V in going to the 5V out from the turnigy switch. When the turnigy switch gets a PWM signal over a certain value it closes, sending the 5V down the USB wire to the camera where CHDK sees the pulse and fires the shutter.

                I had it working both ways, but this was much more reliable.  I had erratic results with my hardware using the other methods mentioned in this topic.

                @GocGoc - Mine is on a PixHawk in running APM:Plane.

                • GocGoc > Steve Pharis September 11, 2014 at 4:26pm

                  Thankyou Steve, would it be possible for you to share your pixhawk parameters that enabled the camera to be triggered by distance using that Turnigy switch.  I am just soldering up that switch now to hopefully copy your success.

                  • Martin Poller > GocGoc October 1, 2014 at 10:21am

                    GocGoc, thanks for that, sorry the post seems to have gone out of sequence, I have a Gentwire, which I have tried unsuccessfully, even with a 5v feed to the servo rail, but I'm going to give it another try before I order a PWM switch. :)

                  • Martin Poller > GocGoc September 30, 2014 at 2:16pm

                    @GocGoc  was the switch that I linked to the correct one to use and have you managed to get it working now.Would you mind describing how you have connected it up please. Thanks Martin.

                • Martin Poller > Steve Pharis September 11, 2014 at 1:43pm

                  Thanks Steve, was it this switch that you used?

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