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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Thanks Reuben.

Sorry to hear about the illness in your family.


Family first. Thanks for checking in Reuben.

Hi Reuben,

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

Many thanks.


Yeah... That picture is one of the first - using your two transistor design. Thanks! Played with the circuit board and using Reuben's single transistor. Smaller now.

Hello Brian, there was some change in the Reuben's circuit to get smaller?

No change. It's exactly as designed by Reuben. Two 220k resistors and a 547 transistor. Circuit board by me. Cut with a Shapeoko CNC router. Tabs on the end of the board to anchor the wires with hot glue.

Thanks for sharing the photos before I asked, I was very curious. Thank you Brian!

Thanks Reuben.

Hi members, Skysight MONO is now back in stock, Sony Multiport trigger solution! Visit www.skysigh.eu to learn more about this camera trigger. Have a great day guys!

Hi Guys .. Update 

Ok this is mainly for Iskess, Waladi , etc 

I have made some new cables they can be used for either Canon or Sony depending on the end pug you use .. as you can see on the attached photo .. these are inter changeable,  So I will be sending units out this week So if you have not paid please send purchase amount $25 usd to me soon .. and your updated address, I know someone (Iskess) have paid already but did not receive from the first batch. due to postal issues, so I will be sending a replacement cable out FOC for him only.

Bad news .. I have to go back overseas again on the 19th to take care of family business:o(  as most of you know from my last disappearance.. I will be gone another month plus a week or so ..

Good news is the new cable can also be used as an RC switch for Led lights, flour bombs or anything else you need to switch on and off. it has a 2 amp rating .. and uses the pixhawk 3v signal line to operate ..if you need to add voltage on the red wire .. you could use either 5v bec on the FC Aux pins or separate 12v line  

Also please note this is not a commercial venture I am only making a few cables to help out fellow enthusiasts  

Paypal to ziwi@eol.co.nz

Thank you Reuben,
Looks like you really refined this cable to have many uses.
Looking forward to it.
I wish you the best with your family difficulties.

Hi Reuben,

Great cable!!

Any chance you will publish the diagram and parts if any one required it?

Btw: I send you pm.



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