Building a remote interface for Canon ETTL flash interface

I haven’t posted for awhile.  I’ve been busy with more demanding tasks.

I think I’ve done enough research into the Canon ETTL interface and I believe I now can build a prototype that connects to the Camera and provides control of one or more additional flashes, wired or wirelessly, including other Canon ETTL flashes.  My understanding is that the Canon flash IR mechanism doesn’t really work too well (high noise, low range, etc.), and this interface would potentially allow the use of RF for communication and allow >4 ETTL flash units over a larger distance.  I believe my solution should have a interface that connects to the camera’s ETTL hot-shoe (call it the “master”) and a remote interface that provide an effective ETTL hot-shoe for connection to each flash (call them the “remotes”) you want to control.  The master would be able to set the different remote flash intensities and control remote flash occurrence.  I don’t see any reason for limiting the number of remotes other than the user interface on the “master” to setup the different remote parameters.   This interface should also allow the high-speed sync mode to work correctly with the camera for any flash.

This would be similar to the commercial pocket wizard, but would take advantage of the ETTL interface and ETTL flash controllability.

I hope to finish the prototype soon.


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12 Responses to “Building a remote interface for Canon ETTL flash interface”

  1. Boris Says:

    Hello Bill,

    First thank you, for all your work on the E-TTL protocol decoding…

    I’m working on a small project: I want to add a 2nd curtain sync functionnality to my PWs.

    To do that i’ll be interfacing a PIC on the Hot shoe using e-ttl, and the PW on the top of the PIC.

    The only issue I have (for now) is the electrical interface between E-TTL PIC…

    Wich solution do you use for your prototype?



    • billgrundmann Says:

      I have used PIC in the past, but now find Arduino easier and cheaper for prototyping.

      As far as 2nd shutter curtain operation, I’ve had another post describing how I characterized the 1st and 2nd curtains for my camera. I haven’t found anything in the ETTL protocol that seems specific to 2nd curtain – although, that may be because I haven’t tried it yet. I was planning to use the information about shutter-time to know when the 2nd curtain is happening relative to the flash command. That way I can position the flash pulse anywhere I want inside the 1st and 2nd curtain timings.

    • aw Says:

      Did a some googling for canon being interfaced with arduinos and ended up finding this blog. I have been curious about the canon ettl protocol for a while and I think you’re the first to have really attempted to read it beyond “it is a propriety canon communication scheme” neat to see, but a bit beyond me.
      Hope to see some more updates in the future especially in terms of second curtain sync. Maybe one day the data can be interpreted and used on wireless manual strobes to make them smarter

  2. Jacks-Pixels Says:

    Excellent blog.
    I’m looking to make a remote trigger for my flashes too ! I’vent think to build a full eTLL system but after looking to your blog it’s maybe possible.
    For the moment I’m planning to build a simple remote trigger with multichannel. Some of my friends are competent on xbee RF componants so I think we can build a long range reliable system !!!
    I’ll take a look frequently to your site … if you’re interested to exchange some hint and tips it’ll be a pleasure !!

  3. Jon Senior Says:

    Some interesting work. I was a part of the team working on the “Strobit” open source flash trigger, but work commitments forced me to step down. My current project is to hack the AF assist light out of a old 300EZ flash to use as a standalone AF assist. I don’t suppose that in your studies you’ve discovered under which circumstances, the ID pin is pulled high?

    I presume that the camera needs to believe that there’s a flash in the hotshoe in order to try and use focus assist, but I’m not sure whether that needs to be just the presence of a foot in the hot shoe, or whether I’ll need to actively pull certain pins high / low.

  4. Adrian Says:

    Great work Bill; really useful!

    Incidentally I suspect the reason you see 8C rather than 86 is that you’re using ETTL-II hardware, the data mentioned on is for standard ETTL.

  5. Mathew Levett Says:

    Hi there, great work with this so far and any luck with your prototype? I have been trying to work out how to build a wireless repeter for the signals that simply reads them in on the hotshoe, transfers them via radio to a reciver that converts it back to the pins on the flash hotshoe. Unfortuntly its been a while since I did electronics so have become stuck. do keep us updated on your progres though 🙂

  6. Savanture Says:

    Is anybody here? billgrundmann, what happened with your research? You’ve maid a really great job, so did you do a final document?

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