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 Craig,

thanks for sharing! I came across it some time ago and was wondering why it hasn't been mentioned earlier - but maybe I just missed it :-) I am sure it has great potential. The only thing which makes it less attractive for mapping is the weight. It is the board, the cables (USB Type A) materials to mount it, ... Hence, for long endurance mapping missions smaller devices based on Marco's and Reuben's circuits have an advantage. Based on Za Pf's PCB you can make a device of about 2g incl. cables (see below). But for sure it is missing all the flexibility of the OpenCCB.

So Kickstarter or Indiegogo is a good idea I guess.



Fantastic! Will it work with a Sony NEX or a5100?

With the appropriate cable, yes. the a5100 uses a different pin for activating the shutter. you can find a cable on ebay and modify it, that is what I was planning. chdk / canon cameras just need the 5v and ground lines on any standard mini / micro usb cable

CHDK method does not seem future proof as of today's canon camera generation, if I understood well. This is because canon uses new chips inside their cameras that don't allow CHDK anymore. Am I right ?

You are not right.

I think what you are referring to is the use of the new Canon DIGIC6 chip in some of the newer Canon high end models and the DIGIC4+ in some other models.    The DIGIC4+ has been hacked in several camera models and there is at least one hack for a DIGIC6 based camera so far.  

These changes have slowed things down but not stopped them. This is not the first time the CHDK developers have needed to overcome such obstacles.  The entire camera operating system actually changed a few years ago for example (from VxWorks to DryOS).

Nothing is future proof.  Canon could go out of business or stop making P&S cameras for example.  Or Canon could make a simple firmware change and lock out CHDK forever.  But they have not done so for over eight years now.   And in the worst case scenerio, there are thousands of used and reconditioned cameras out there suitable for UAV work - a situation that is unlikely to change for a long time.

I'm sorry about my poorly worded question, I know about the multiport plug requirement for the Sony cameras, that's what I'm using. I was wondering if the Open CCB could control other functions on the Sony, namely focal length. Imagine if focal length could be controlled automatically by the Pixhawk to adjust in relation to the terrain data. We could fly level flight lines and maintain a constant GSD (within the constraints of sidelap and overlap)

Other than gaining more camera control, what advantage does the Open CCB have? Is it simply that I can find the log files on the camera's card rather than the Pixhawk's.

Hello Walter,

What do you think about AF lamp flashing at the time of the shooting? You have developed a script for that?I read some posts about it, it seems a good solution for the moment.


Plínio Augusto 

The board is designed to communicate to a Sony Lan-c protocol enabled camera.  I don't know if either of those camera support Lan-c

Yes that is what I was referring too. Thx for the info, this is good news CHDK found hacking ways through these new chipsets. Let's hope it continues like that.


As the thread did not show a simple circuit to trigger a Sony Alpha camera yet, here is one I made and tested succesfully today.

Some explanations to trigger Sony cameras with a multiterminal port  (also named a S2 port): to trigger , you need to short two pins (=focus & shutter pins) to the ground. That is interesting because we do not need any power up circuit from the Pixhawk 3,3V to 5V (like CHDK/Canon cameras would require). We just need a "switch" circuit that will connect the focus, shutter and ground pins of the S2 port. This can be done with one transistor as shown in the schematic/picture below:

Note that in addition to making this small circuit (less than 1€), you need to buy a S2 cable (can be found for 10-15€ online).

Erratum: the circuit above, while working on a battery, I could not have it working on a Pixhawk relay port. I'm troubelshooting why.

Is there a little residual voltage leaking from the signal pin when the Pixhawk relay is in the off state? It doesn't take much to trigger the transistor.

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