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DryOS receive data from UART

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Offline bootstrap

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DryOS receive data from UART
« on: 07 / December / 2015, 22:33:32 »
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I am looking to use a position from an external GPS receiver for the geotag position the camera writes.

The output from the GPS receiver is NMEA sentences over a 3.3 v UART, for simplicity it would be ideal if a UART on the camera is used to receive the position.

The camera I have is a SX260, which runs DryOS and has an internal GPS already. A 1.8 v UART is accessible on the SX260, with the same footprint as the SX230 and others.

After reading the CHDK wiki and forums the best I can understand is that receiving UART data on cameras running DryOS is not as straight forward as transmitting data.

I am new to CHDK and am looking to find out if this approach is possible or a dead end.

Most informative forum post:
http://chdk.setepontos.com/index.php?topic=11029.20

Kind regards.
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Offline reyalp

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Re: DryOS receive data from UART
« Reply #1 on: 08 / December / 2015, 01:04:04 »
Quote from: bootstrap on 07 / December / 2015, 22:33:32
I am looking to use a position from an external GPS receiver for the geotag position the camera writes.
Note that even if you get the data from the UART, quite a bit of work will probably be required to actually tag the files. Logging with timestamp and combining later might be more efficient. Taking that a step further, you might be better off just using a GPS that logs by itself without involving the camera and geotag after the fact.
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After reading the CHDK wiki and forums the best I can understand is that receiving UART data on cameras running DryOS is not as straight forward as transmitting data.

I am new to CHDK and am looking to find out if this approach is possible or a dead end.
I'm not aware of anyone having done this. It should be possible, but it will take some reverse engineering.
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Most informative forum post:
http://chdk.setepontos.com/index.php?topic=11029.20
The stuff in that thread might help you find some starting points, but what you want to do is sort of the inverse. There might be a simpler way to be found looking at how drysh etc get their input.
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Offline bootstrap

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Re: DryOS receive data from UART
« Reply #2 on: 08 / December / 2015, 05:04:13 »
You are right, using the GPS tracklog to add the geotag afterwards would be less effort while achieving the same result.

Another option could be to use a SBC to send the GPS data to the camera using PTP. I'd still need to work out the geotagging part. It's also more hardware to cart about.

There would be applications where a functional UART is useful, for instance interfacing with a microcontroller. The Canon UARTs are difficult to access, but I believe some Samsung cameras have the UART pinned out on a large connector.

Thank you.

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Offline reyalp

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Re: DryOS receive data from UART
« Reply #3 on: 08 / December / 2015, 21:14:09 »
Quote from: bootstrap on 08 / December / 2015, 05:04:13
You are right, using the GPS tracklog to add the geotag afterwards would be less effort while achieving the same result.
A common problem with this approach is most cameras RTCs drift quite quickly, but sx260 can set it's time from GPS, so you could just sync it once a day or something and be quite close.
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Another option could be to use a SBC to send the GPS data to the camera using PTP. I'd still need to work out the geotagging part. It's also more hardware to cart about.
Yes. A raspberry pi zero should work pretty well for this. You could also transfer the images to the SBC and tag them there, which would let you use standard software like exiftool or whatever instead of writing your own.
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There would be applications where a functional UART is useful, for instance interfacing with a microcontroller.
No argument there.  I'm not trying to discourage you from taking this approach, just suggesting alternatives if you aren't in a position to do the reverse engineering work.
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The Canon UARTs are difficult to access, but I believe some Samsung cameras have the UART pinned out on a large connector.
May be true, but most of the work to set it up for CHDK is unlikely to be relevant to Samsung cams.
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