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07-18-2011, 09:32 AM   #16
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Just like any of the Pentax flashes that communicate with the camera - I have several - I think the GPS will be just be another device passing data along via the hot shoe data contacts. There should be little overhead to the data transmitted. Heck, the data string from the GPS would probably be less than 1k, since GPS data only has so much info.

But again, I don't know 100% since I don't have a GPS device.

However, if I was working the software, I would be programming a device identification bit, that the camera is looking for when it is reading data along the hot shoe bus. I would be VERY surprised if Pentax didn't already have code that identified different flashes on the hot shoe. The GPS device would easily co-exist with other devices, just as you can daisy-chain flashes with F5P extension cords.

07-18-2011, 09:36 AM   #17
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QuoteOriginally posted by adr1an Quote
Have you confirmed this with Pentax ? If you think what the GPS is doing (Passing Binary encoded data to the Camera containing a rather length NMEA statement, or passing it in a longer plain-text string, Along with Gyro and Compass Data...) - then as I said earlier:

I will be very intrigued if it works with Both the GPS *and* a TTL flash doing TTL... Manual I see working fine... but not TTL and the GPS....

Thats the bigger issue.. not the physical dimensions/fitting of it... its the clashing of the TTL data.. and the fact the camera is obviously going to make a decision about how it handles TTL when using a GPS (which also is using TTL - or at least the same physical pins...)
True. We'll see how it goes. I'll bet you and I would love to see some code samples!
07-18-2011, 09:52 AM   #18
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O-GPS1 contacts from this blog
Flash Features and Operation

From a technical standpoint, I can imagine several reasons why it could not work. And if Pentax officially is stating (see above, if the google translation is correct) that usage of O-GPS1, hot shoe adapter F and external flash is not allowed, this could also imply that Pentax then does not even exclude possible damage of flash and/or GPS and/or camera (-> no warranty). At least, I would very carefully read the corresponding O-GPS1 manual before any attempt...
07-28-2011, 09:19 PM   #19
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So has anyone tried this with pc-sync socket yet? I'd be curious to know if that works okay (for non-TTL, obviously)

Incidentally, it's not entirely accurate that the communication is done on the "digital" pin. In fact, it's actually the "control" pin - the pentax hotshoe has 5 contacts, Pentax labels them C,R,Q,X and G (Control, Ready, Quench, X sync and Ground). I notice the O-GPS1 doesn't have the X pin, which makes sense.

For a digital capable flash (ie, one which has the C pin), the C contact is pulsed a certain number of times to initiate communication; the number of pulses indicates Camera->Flash communication, Flash->Camera communication, or different forms of flash emission (pre-flash, uniform, HSS etc).

The subsequent communication data (or emission sequence) is carried out in synchronous mode on the R and Q pins, using R for a clock and Q for data, where the direction of data flow is determined from the previous count of C pulses. For emmission commands, the pin designation is a little different.

So it is possible they incorporate camera/GPS communication either by defining new versions of the C pulse string (ie more pulses), or subsume it into the existing camera<->flash communication string events.

- Peter


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