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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I never had any problems with my APMs. Does this happen in flight? However, I am using CAM_TRIGG_TYPE = 1 with this setup. I guess TYPE = 0 is required for the gentWIRE cable. Or?



I've had it happen multiple times on my Pixhawk when I was testing it on the work bench. I thought for a while that just going to the "Extended Tuning" page in Mission Planner was resetting it to "0" but that's not the case. I've been unable to duplicate the cause of the problem. But between that problem and the challenges to getting CHDK scripts working properly the LED is very helpful in steering me to what needs to be fixed.


ah ok, you are also using TYPE 1 (I got it the wrong). So I'll have some closer look at it. Concerning CHDK scripts the S110 seems to be not as easy to handle compared to the ELPH 110. So, if anyone has a working script for this one... :-)

What camera(s) are you using? 

Kind regards,


That looks great. Thanks for posting. I also like the idea of adding an LED trigger indicator

I started out with the S100, which I already had, for doing 360 degree panos from my new Hex with RC Timer ASP gimbal but ran into the blurring problem. I then bought an A2300 off eBay to try. The A2300 does not have optical IS so the pictures were not blurred, but it has some severe limitations on exposure control, even with CHDK. I bought an S90 off eBay this week which should arrive today. I'll do some testing tomorrow and post my results. At least one user reported success with the S90 earlier in this thread, the optical IS may be less susceptible to vibration since it was the first S series with IS, we'll see.


yes, that is missing in the wiki so maybe you can merge it somehow. I also like the idea of an LED for testing. However, it is rather strange (i.e. it must be a bug) that CAM_TRIGG_TYPE will sometimes reset to 0. I never had any problems with my APMs. Hence, an LED should not be required under normal operation. It also does not prevent you from not switching your camera on ;-) I always use Ch 7 to trigger the cameras at least once before arming to make sure they work.

Kind regards,


Like others, I was disappointed with the performance of my Canon S100 camera on my hexacopter (Tarot 680 Pro with RC Timer ASP gimbal) so I decided to do some testing on the S100 and a couple other Canon cameras. I ran a couple of series of 10 photos of the same scene using the S100 from the hexacopter while in flight. Only about 20% of the photos were usable, the rest were blurry. When I did a flight of the same scene using the S100’s HD video mode I could see the problem. There was some type of resonance with the vibration of the hex as the props when in and out of phase. The video cycled from sharp to blurry and back, with the blurry part being about 80% of the cycle.

One previous member suspected that the lens barrel might be rattling around since it’s loose. I tried taping the barrel to prevent it from moving but there was no change. I also tried adding a 100 gram weight to the gimbal thinking that the added mass might change the dynamics of the gimbal. There was no change, still only 20% good images.

In researching Canon cameras, I found that the A2300 does not have optical image stabilization and there is a version of CHDK available for it. I purchased one off eBay and loaded it up with CHDK 1.2 Alpha. The 1.2 version of CHDK on the A2300 is buggy, so I tried the current development version of 1.3, it works perfectly. I tried the same scene shot from the hex and got pretty good jpg photos. The RAW (DNG) photos have the potential for better quality but they take a lot of processing to get anywhere close to the jpg photos. Using Photoshop RAW, I was able to get close to the jpg quality but not equal it. The A2300 does have some limitations. It doesn’t have a normal iris. It has an ND filter so you can get either f2.8 or f7.9, nothing in between. I set it for 1/1000 second and locked out the ND filter, then used the manual ISO setting for exposure control. See the attached image labeled A2300.

One other member said they got good results using the Canon S90 so I bought one of those on eBay. Unfortunately results were similar to the S100 so the S90 is going back on eBay. See the attached image labeled S90.

I considered, briefly, trying out the Canon Powershot G series. The G9 is the most recent version that does not have optical IS and has a version of CHDK, unfortunately Adobe Camera Raw doesn’t have a preset for it. Camera Raw G series presets start with G10, but the G10 has optical image stabilization. I may still try out a G9 just to see how much improvement there is and if it’s worth the extra 200 grams weight. But for that extra weight I could just as well go for one of the versions of the NEX and have HD video also.


I just discovered I was wrong about the G9 not having Optical IS, it does so it's not a viable camera for a hexacopter.

I have this working as a relay in APM Plane, but I am unable to use a channel to trigger the camera.  I have set RC7_function to 10: camera_trigger and channel 7 assigned to a switch, but it doesn't trigger the camera.  The camera triggers fine based on distance.  Plane doesn't have the channel 7 option setting like copter.

Anyone have an idea?

You have to choose between RC control (pass through) or APM control.
Use 10 for APM control or 0 for RC Pass Through.

Servo activation just doesn't work.  Same issue as many others have reported - the pulse bounces between 0 and 10-11 according to chdk.  Whether through passthrough or servo on any channel, the trigger will not fire using the methods in this thread.  I think a better route might be to get an actual relay and just run a basic remote script.  Relay works just fine on any AUX channels, but in plane, I do not see a method to take control of that manually - only distance or mission trigger.

Sorry, I'm using a PWM (servo) based shutter trigger. I use the one from Flytron, it's similar to the Genwire. If you are using the relay method you will need an LED switch. Check out Duffy's tutorial: http://flightriot.com/remote-sensing/trigger/

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