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hot swapping SDHC cards

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hot swapping SDHC cards
« on: 30 / January / 2012, 20:33:45 »
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the lens barrel on my G9 stays extended when I hot swap SDHC cards.  i'm wondering if CHDK has been designed to tolerate hot-swapping?

the application would be to have the base CHDK on one small capacity card, and scripts on larger capacity cards. this would make it more flexible to share scripts with other people in the field (at a photo shoot) without worrying about a match at the  firmware level

if CHDK has not been design/tested for hot-swapping, then the consequences are undefined and I won't pursue doing this.  Still, I'm curious to know the good answer about CHDK's design objectives.

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Offline reyalp

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Re: hot swapping SDHC cards
« Reply #1 on: 30 / January / 2012, 22:35:59 »
CHDK in the 1.0 release would probably be OK with hot-swapping (caveat this is off the top of my head). There could be issues with the CFG file, but I think CHDK would just save the current settings on the new card the next time you went in and out of alt.

I'm not sure the Canon OS would be OK with it. Most of the cameras share the battery compartment and SD card, and shut down when you open the battery door. I didn't look carefully, but I didn't see anything one way or the other in the G9 manual.

IIRC some users reported doing this successfully a long time ago.

The development trunk (1.1) would be more problematic, since it expects to load modules from the SD card at run time. If you had all the modules on both cards it might be OK

Overall, I wouldn't do it with any data I cared about. Cards are cheap, just configure them with whatever you need. If you need to have the same scripts on a bunch of cards, just set up a batch file or something to prepare the cards or upload the latest scripts over ptp.
Don't forget what the H stands for.

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Offline philmoz

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Re: hot swapping SDHC cards
« Reply #2 on: 30 / January / 2012, 22:43:05 »
If the camera firmware caches any parts of the SD file system structure in RAM, then you run the risk of corrupting the files system on the swapped card.

All my cameras beep very loudly at me if I open the battery door without turning off the camera - I'd be suprised if the G9 was different, unless the compartment door switch was broken.

Phil.
CHDK ports:
  sx30is (1.00c, 1.00h, 1.00l, 1.00n & 1.00p)
  g12 (1.00c, 1.00e, 1.00f & 1.00g)
  sx130is (1.01d & 1.01f)
  ixus310hs (1.00a & 1.01a)
  sx40hs (1.00d, 1.00g & 1.00i)
  g1x (1.00e, 1.00f & 1.00g)
  g5x (1.00c, 1.01a, 1.01b)

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Offline reyalp

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Re: hot swapping SDHC cards
« Reply #3 on: 30 / January / 2012, 22:54:06 »
If the camera firmware caches any parts of the SD file system structure in RAM, then you run the risk of corrupting the files system on the swapped card.
Unless the cameras with a separate SD card door do something special this is definitely the case. The battery / SD card door is a software switch that does a "safe" shutdown of some sort before you can actually open it and remove the battery or card. If there was nothing to worry about from pulling the card or battery, they wouldn't spend the money on that component ;)
Don't forget what the H stands for.


Re: hot swapping SDHC cards
« Reply #4 on: 30 / January / 2012, 22:58:31 »
Unless the cameras with a separate SD card door do something special this is definitely the case. The battery / SD card door is a software switch that does a "safe" shutdown of some sort before you can actually open it and remove the battery or card.
Isn't it bypassed in several CHDK cameras ( G10 & SD940 ) - based on something you found reyalp ?
Ported :   A1200    SD940   G10    Powershot N    G16

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Offline reyalp

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Re: hot swapping SDHC cards
« Reply #5 on: 31 / January / 2012, 00:52:29 »
Isn't it bypassed in several CHDK cameras ( G10 & SD940 ) - based on something you found reyalp ?
True, but the fact Canon put in the hardware and software to do that suggests they were worried about the card or hardware being left in a bad state if they didn't.

Hmm, I don't actually think that should be overridden by default in the autobuilds...
Don't forget what the H stands for.

 

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