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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Ok .. new cables ready to ship.. I will be sending out this week so if you wanted one be quick otherwise I will be off the radar for a while..from next week ..

Cable $25 usd Postage $10 usd 

Hi Nejc,

Did u move around 1 meter and test if its triggering for cam_Trigg_dist.

It might be triggering randomly because of gps variations, when gps loses or gains a sat signal there will be distance change so it triggers, try changing distance to 5 to 10 meters and try.

Hello everyone,

Hhow to solve the delay problem in shots on CHDK? When the signal is sent to camera takes a while to shoot, there is a way that shooting happen faster? Perhaps for this reason Ebee uses Canon without CHDK. Probable Ebee connect the trigger cable directly to the canon shutter button. We realize the difference by aligning the blue and green balls during image processing in Pix4D. Any help is welcome.


Chasing the camera delay from CAM trigger message to shutter open is futile. Feedback from the camera to the autopilot is required. It's being addressed here:




Thank you very much!

I made a version of reuben's circuit and put it on oshpark. my breadboarded version worked, still need to test this one. Very cheap if you want to build it yourself however.


I'd like to be able to provide the cables required for sony cameras (a5100 / a6000 etc) as well. I'm going to start wading through this thread again, but does anyone know the particular pinout needed for that? I was under the impression the sony plug is just a micro usb with a different pin connected for the remote trigger. I guess I could manually strip this for use: http://www.ebay.com/itm/231256005313?ssPageName=STRK:MEWNX:IT&_...

I'm guessing its the ID pin (used normally for otg cables and such) or am I mistaken and its completely proprietary?

Hi Za Pf,

thanks a lot for sharing! I have only tried Marco's circuit so far (see page 6) and it works great. But your design is easier to handle. I'll try it for sure and I hope they'll place it in the wiki!



Again, I must stress that this is not my design. This was posted earlier, and there is an example from Brian Christal on the previous page. I just wanted to make one as cheap and easily accessible as possible.

Hi Za Pf,

I know. There have been lots of reposts here and everything is a little chaotic.

You posted the brd files and that really makes things easier!

Thanks to everyone who contributed!


Hi Guys 

Has anyone have any trouble getting a APM2.5 to run a relay on A09 .?.its supposed to have 5v logic but refuses to operate a 3v relay with a coil load of only 16ma ? when i operate the trigger from MP I only get 2.5v on A09 pin.

Regards Reuben

Hi Thorsten

I'll try it for sure and I hope they'll place it in the wiki!

Who is this "they" you speak of :-) Were you thinking this should be added here? I don't think this can be added as is - minimally should have labels or diagram which shows what components go where on the pcb. Did it work OK?



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