Hi All.

I have started an identical topic on the CHDK Forum, as it relates to a Canon SX260HS using CHDK/KAP_UAV: https://chdk.setepontos.com/index.php?topic=13028.0

I'm having issues with the focus assist LED in front of the camera: I want to use this LED, trough a phototransistor, to capture shutter opening signal and send it to the time-mark pin of an ublox GPS for accurate time-stamping.

User Waterwingz (creator of the KAP_UAV script) has been most helpful and supportive, and we're still trying to figure out why the LED pulse width is so erratic as not to allow to use it for what I intend to.

I thought I also post it in the DIY Drones Forum to see if anybody else has succeeded in capturing the LED pulse from a Canon SX260HS.



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Am interested to know if you got any further with this... I have read your thread on CHDK forums and have posted myself here:


and here about it:


Why do you use the time mark pin on the uBlox instead of the feedback pin on the Pixhawk? Is it more accurate that way? And where do you get the log from? Is the time-mark recorded in the pixhawk logs? Does this interfere with routine GPS functions (auto mapping missions, loiter etc) or do you have two gps's, one for the aircraft, and one for the camera?

Giovanni - iGV Helo, Canon SX260HS already has its onboard GPS no need to geotag pictures. You can do post Geo-correction in GIS using existing features or orthorectified satellite imagery if needed. 

Indeed it's one of the best cameras for photography today. Cant wait to have one.

Hi; I was not able to consistently capture the LED upon shutter activation, so I decided to replace the camera with one having a hot-shoe (a Nikon DSLR).

Sandy - I prefer using a separate GPS to avoid overloading the Pixhawk; maybe that's not the case, but I prefer separating flight control stuff from other non related calculations; also, having a separate GPS dedicated to the camera means a cleaner log to process.

Stanley - Yeah, I know the SX260 has internal GPS, but it's not as accurate as a ppk approach yields. 

Ok, thanks for that Giovanni, it sounds sensible to have a seperate GPS. Do you use a uBlox for the Pixhawk also? So that both GPS systems are identical and get "identical" positional readings (offset by their physical distance apart?).

And do you use the "PIXHAWK" USB shot control mode in KAP UAV?

Hi Sandy.

I use an u-blox M8T to acquire raw gps data that are then post-processed, and don't really use the Pixhawk gps log data.

KAP UAV us set to one-shot.

Thanks Giovanni, useful to know you use oneshot. I think it is possible to get faster response times from the camera using the PIXHAWK shot control mode...

I follow what your saying that you use a seperate gps for logging camera position, I am asking if you are using the same type of GPS on the aircraft as you do for logging with your camera...

And what do you log the GPS data to? Do you have a rPI or something similar to record and retrieve the GPS data from?

The camera shutter logs on to an ublox M8T; the Pixhawk uses its dedicated 3DR GPS unit (M8N, I believe).

The M8T logs to a simple SD card logger connected to the GPS board (no sbc used).

Thanks Giovanni, your set up is very interesting!

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