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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

        • iskess > SkySight April 1, 2015 at 6:06pm
          Not seeing the pdf. I take it that's a NO for relay control?
          Would you mind describing the 4 modes here rather than making us hunt for the info.
  • Arshish Maneckji March 23, 2015 at 11:01pm

    Hi,

    Can someone help me with this please. I have been able to get this to work with a Pixhawk and Marco's circuit but the only value returned by get_usb_power() is 116.

    The WIKI suggests I should get a value between 5 and 16 but as I get 116 I get an error message.

    if k < 5 then gosub "ch1up"
    if k > 4 and k < 8 then gosub "ch1mid"
    if k > 7 and k < 11 then gosub "ch1down"
    if k > 10 and k < 14 then gosub "ch2up"
    if k > 13 and k < 17 then gosub "ch2mid"
    if k > 16 and k < 20 then gosub "ch2down"

    To get going I have modified the script to execute the command I want when the a value of 116 is returned so its working for me now..

    However I would like the ability to execute different routines. Can some point me in the right direction so that I get correct values from the get_usb_power() function. I am using a Canon A2400 IS camera with CHDK 1.3

    Thanks.

    Arshish

  • Spyros March 21, 2015 at 3:51am

    Hi all,

    Thanks very much for the useful info. I myself have been trying to setup the Canon HS280 to be triggered by the Pixhawk that has a BEC 5V connected to AUX rail, with no luck. Since I am very bad in building circuits, I would like to confirm please that if I buy the 132 gentWIRE-USB2 Canon cable I will be able to trigger the camera with pixhawk flying in a predefined waypoint mission. This cable contains a circuit similar to what Marco advised?  Should this be cable be connected to the AUX ports or the relay ports?

    I would also like your help if possible in understanding what is the difference between the pixhawk's AUX ports and the "relay" or "digital" ports.

    Thanks very much for your help

    Spyros

    • Eric Coronel > Spyros March 21, 2015 at 8:11am

      The gentWIRE cable by itself doesn't work.

      • Spyros > Eric Coronel March 21, 2015 at 9:07am

        Hi,

        Thanks for the reply. You mean it is not sufficient to trigger the shutter . What else is needed with it?

        Has anyone tested this using a strattosnapper?

        Thanks

This reply was deleted.

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