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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

            • Plinio Augusto > Reuben April 24, 2015 at 6:52pm

              Thanks Reuben.

            • Waladi > Reuben April 20, 2015 at 6:17pm

              Hi Reuben,

              I hope that I can get several cables also as agreed :)

              Many thanks.

              Waladi

            • iskess > Reuben April 20, 2015 at 9:45am
              Family first. Thanks for checking in Reuben.
            • Bill Isenberger > Reuben April 20, 2015 at 5:54am

              Thanks Reuben.

              Sorry to hear about the illness in your family.

              Bill

        • Wiki Ninja
          Hamish Willee > Bill Isenberger April 19, 2015 at 4:31pm

          Hi Bill

          I've added this cable to the end of the CHDK wiki page here. I figure no point reproducing your user guide in a dedicated page ... and this is the first place people looking for a chdk solution on the wiki will go.

          OK by you?


          Cheers

          Hamsih

          • Bill Isenberger > Hamish Willee April 19, 2015 at 5:32pm

            OK by me.

            Thanks Hamsih,

            Bill

        • Bill Isenberger > Bill Isenberger April 19, 2015 at 10:02am

          I have tested the cable with a 5 volt UBEC and with 4 Afro ESC's with 0.5A linear BEC's. It works both ways. The UBEC gave me 5.33 volts on the AUX OUT rails, the linear BEC's gave me 5.03 volts on the AUX OUT rails.

          I had the UBEC pluged into AUX OUT 6.

  • HighYoyo April 18, 2015 at 10:45pm

    Hi. So I tested Marco's circuit in flight and it worked perfectly. Interestingly, I also tested the circuit without providing 5V to the Aux rail.... and it still triggered my camera!? I don't really understand why. I thought maybe the 3.3V from the PixHawhk was enough to trigger my particular camera model (Canon ELPH 110HS) but no.... I did a test with a simple USB cable and it did note trigger. Does anyone know what's happening? Where is this 5V coming from?

This reply was deleted.

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