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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Hi Brian,

I have a Canon SX260... You know any way to adapt external flash to catch the feedback signal in this model? I also think of using the IXUS 155 20 mp...


Hi Plinio,

Yes, sort of. There is a beta version of the KAP UAV script that lights the red eye lamp when the shutter opens. I'm working a cable now that uses a phototransistor to read the lamp and send a feedback signal to the Pixhawk. But, the cable is not ready yet, nor is the ardupilot firmware.

I don't think CHDK is available for your IXUS 155.


Exactly, I was reading now that the CHDK for IXUS 155 is not ready yet. Thank you for your answers you are helping me a lot. I will follow your way.



The link to the beta version of the KAP UAV from chdk.setepontos.com is broken, you could provide the beta file?I would like to implement this function in 3DR_EAI_SX260.lua script ...

Hi Hamish,

Who is this "they" you speak of :-)

The power, the force, the motion, the drive! :-) 

You guys are doing a brilliant job on the wiki! Thanks!

The problem with this circuit stuff is that it is not straight forward to build your now board based on Marco's circuit or the derived version which is now posted on the wiki. Hence, a while back, I posted a more detailed how-to.

But now I saw the Za Pf's brd files which he made available on OSH Park. I haven't tested it so far (just ordered it) but I think this is the way to go. And before it gets lost in the "Ning-space" I hope that it will be placed more prominent. I agree more details are required.

The design is from Reuben and is based on two 220k resistors and one 547 transistor

I'll post some details when I tested it.



Hi all,

I came across this problem (again) some days ago. I opened an issue before looking back here... Anyway the bug still exists.



Thanks - feel free to contact me directly when you have the details and I'll upload the file to the wiki.

Actually,  while setting the output type to CA-1 is wrong for what you are doing, it also will not hurt.  When CHDK is running a script, the USB remote setup values for input and output types in the CHDK menus are ignored.

Hi Brian, 

Sorry for my mistake. Now I realized that I must work to help KAP UAV Script come first with this technology.

We have this Open Camera Control board http://planner.ardupilot.com/wiki/other-project-and-common-topics/c...

that listens to the MAVlink stream for camera control trigger messages and will send CHDK commands to a camera.  It also writes a logfile to the SD card in the camera with Time,Lat, Long, Heading, Pitch, Roll, Altitude annotation information as each photo is taken.  At the end of the flight the file can be read and used to populate the EXIF data for each photo.

The board has been finished for about 18 months but 3D Robotics decided to not produce it.  It is open source hardware and software and we are looking for other companies to produce the board.

I have spoken with a few manufacturers but I would be interested to talk with more.  Also is there enough interest in this group to purchase the board if it is manufactured ?


Thanks for sharing your response. Perhaps the solution is in Kickstarter or Indiegogo.I would be happy to buy your board.  I'm sure many people are in need of this board.I think most people have not understood the importance of making georeferenced images with precision timing.

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