Using AUX pins as relays for CHDK

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

      • @Shad, I agree, I can't imagine that the step-up converter requires that much current.. I have an email into 3DRobitcs asking if the NCP1402-5V Step-Up board is right for this application. I've asked if they could recommend another Sparkfun board if this is not suitable. I'll post the results as soon as I hear.

      • Developer

        Yes, normal npn and pnp.

    • Developer

      My system work fine and require 5 minutes for build this simply circuit.
      In my I inserted a micro fuse to prevent the 5V can go into short circuit affecting the operation of Pixhawk, but it is very unlikely to happen.

      • Hi Marco, maybe an old topic.

        I'd like to add a micro fuse to your setup as you suggested.

        What kind of microfuse did you added? Rated?

        Thanks in advance

      • Thanks Marco, since I already have the SparkFun step-up converter I would like to get it working if I can.

        • Developer

          I've tried with a similar step-up converter and it doesn't work because the 3.3V output is too "low" (is a digital output) and the voltage drop when connected to the step-up input.

  • Thanks for the info everyone. We'll be testing the middle AUX pin w/ the Sparkfun converter this weekend. Seems like a more elegant solution than using an arduino (which will work in a pinch). 

  • Developer

    I recommend using the guide in the wiki

    http://plane.ardupilot.com/wiki/common-chdk-camera-control-tutorial/

    and I will get it updated for Pixhawk

    • MR60

      This is only applicable for people using a Canon camera + chdk. 

      There is nothing yet in the wiki for a NEX camera triggered by a IR trigger for example. I will write a blog about this because I finally made it to work after guessing stuff that should be documented; took me two days of trial and errors with Pixhawk...

      • Developer

        Let me know when you have something written and I'll have it added to the wiki or I can give you edit access and you can add it yourself.  Thanks for your help with this!

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