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Hot-shoe signal to external GPS

Started Apr 24, 2017 | Questions thread
jekain New Member • Posts: 2
Re: Hot-shoe signal to external GPS

I am trying to get an interrupt into a microcontroller at the shutter-open event. I am using a Canon EOSR camera. I hope to be able to use the hotshoe to provide this interrupt signal.  The Canon has 5 connections at the hotshoe plus the ground (rails).

I have tested the pins using a scope. The only setting in this camera that seems to be useful is to set the flash to "enable".

I can set up the oscilloscope to read the time-signal between the 5 pins and ground.  I click the shutter (manually) and can see the response from the pins. I show the oscilloscope connection below. I also show the oscilloscope traces for several clicks.

The only pins that seem to respond are the two "middle" pins. The left pin produces a 5V pulse of two secs duration and the right pin produces a pulse of 3.3V also for two sec. The pulse is initiated at the pre-fire (half-down) button press -- the two sec timer is initiated at the time of the fire pulse. This seems to be highly repeatable.

Can anyone assist with explaining this behavior?

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