Direct Access to external USB HDD for backups - General Discussion and Assistance - CHDK Forum
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Direct Access to external USB HDD for backups

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Offline jon.minhinnick

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Direct Access to external USB HDD for backups
« on: 12 / June / 2013, 21:21:08 »
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OK, so this is going to be a stream-of-consciousness post! Apologies in advance.

I've had something in my head for a little while now, and I've thought about it from several angles. That is, the problem of reliably backing up images from the SD card to an external location while travelling.

When you're on an expensive overseas holiday, whether you're travelling in a 1st World or 3rd World country, one of the greatest disasters that can happen (short of falling seriously ill) is losing your photos. Backup becomes of great importance. I've considered several ways of doing this- bringing a laptop, pushing to the cloud, using those little cardreader/HDD/screen combos and so on, but laptops have a serious weight disadvantage (important when you're lugging all that camera gear), cloud services are expensive and often not available when travelling foreign shores, and those combo units are needlessly expensive (and you already have a cardreader, screen and system clock). The simplest way is to do it in-camera.

So I would like to know- how feasible is it to plug an external HDD (with its own power supply) into the camera's USB port (or probably do it via a USB hub), use CHDK to create a root folder on the HDD using the camera's current timestamp to generate a unique name, and then mirror out everything that's on the current card inside the camera?

This means that extra equipment is kept to an absolute minimum, there are no capacity, bandwidth or weight issues, you can even carry two HDDs for added reassurance and keep them in separate locations.

Assuming it's possible, how easy is this to do? In other words, should I try to accomplish this myself? I'm technically literate (Microsoft qualified server engineer, can script in PowerShell) but have no experience with CHDK. I have yet to even try installing it. OTOH, if it's really trivial, can someone knowledgeable here hack it in 15 minutes without breaking a sweat?

So I'm not submitting this as a feature request if it's something I can do myself but also I won't do it myself if I have no real hope of getting it working successfully.

I'd welcome any thoughts and other feedback on this.
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Offline waterwingz

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Re: Direct Access to external USB HDD for backups
« Reply #1 on: 12 / June / 2013, 21:44:44 »
What you are missing here is that USB is not a peer-to-peer networking medium.  There are masters (your PC) and slaves (devices like mice, keyboards & cameras).  There is essentially no chance that you can get CHDk to make your camera a master and talk to an external HDD.
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Offline waterwingz

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Re: Direct Access to external USB HDD for backups
« Reply #2 on: 12 / June / 2013, 21:58:37 »
Here's a (maybe) better idea.  A raspberry pi is very small computer and can powered from a small "wall wart" (like the tiny power supplies that come with Blackberry smart phones).

You could easily set it up to run a script on startup (no keyboard, mouse or monitor needed) that would look for your camera and use PTP to transfer whatever it finds there to an USB external drive.

Its a couple of extra gizmos but smaller than a laptop.
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Offline reyalp

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Re: Direct Access to external USB HDD for backups
« Reply #3 on: 12 / June / 2013, 22:14:09 »
Another alternative would be a tablet that can act as USB host. Many android tablets should support this. While it is another thing to carry around, a 7" tablet shouldn't be a huge burden, and could come in handy on it's own. I'm not sure what the software situation is like, but I'd expect you can get apps that will both access a mass storage device and a PTP device.
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Offline jon.minhinnick

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Re: Direct Access to external USB HDD for backups
« Reply #4 on: 12 / June / 2013, 22:27:10 »
Android tablets... hmmm... what about Android phones? Probably carrying one of those when travelling too... And not just Android, what about Winphone (which I have) or IOS (I already have an iPad)?

I'm interested in the master/slave thing. I'm aware of it, but is this really fixed in stone? Shurely it could be hacked, as electrically everything you need for two-way comms is already there? Hmmm again, perhaps it's a function of the USB onboard controller...

Questions, questions.
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Offline waterwingz

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Re: Direct Access to external USB HDD for backups
« Reply #5 on: 12 / June / 2013, 22:29:12 »
Quote from: reyalp on 12 / June / 2013, 22:14:09
Another alternative would be a tablet that can act as USB host. Many android tablets should support this. While it is another thing to carry around, a 7" tablet shouldn't be a huge burden, and could come in handy on it's own. I'm not sure what the software situation is like, but I'd expect you can get apps that will both access a mass storage device and a PTP device.
I hesitated to mention this as I have not seen USB host ports on 7" tablets (although two of my 10.4" tablets have them).   Then I remembered that I have what's called an OTG cable for my 7" tablet.  It has an extra pin that tell my Nexus 7 to perform as a host.

Quote from: jon.minhinnick on 12 / June / 2013, 22:27:10
I'm interested in the master/slave thing. I'm aware of it, but is this really fixed in stone? Shurely it could be hacked, as electrically everything you need for two-way comms is already there? Hmmm again, perhaps it's a function of the USB onboard controller...
The limitation is the size of the software stack necessary to support the host side of USB communications - its not a hardware limit.
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Offline jon.minhinnick

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Re: Direct Access to external USB HDD for backups
« Reply #6 on: 12 / June / 2013, 22:36:21 »
Ah. This explains a few things about the master/host relationship, but it's not clear whether this is implemented in hardware, firmware or software:

https://en.wikipedia.org/wiki/USB_On-The-Go

Might have to find a USB On-the-go device and hack that instead. Sheesh, does that mean I have to learn to program a winphone?!?  :o
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Offline philmoz

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Re: Direct Access to external USB HDD for backups
« Reply #7 on: 12 / June / 2013, 23:00:45 »
Quote from: jon.minhinnick on 12 / June / 2013, 22:27:10
Android tablets... hmmm... what about Android phones? Probably carrying one of those when travelling too... And not just Android, what about Winphone (which I have) or IOS (I already have an iPad)?

I'm interested in the master/slave thing. I'm aware of it, but is this really fixed in stone? Shurely it could be hacked, as electrically everything you need for two-way comms is already there? Hmmm again, perhaps it's a function of the USB onboard controller...

Questions, questions.

There is a camera connection kit for iPad that allows you to transfer images from the camera via USB or SD card reader (in the kit).

The problem with iPad and other tablets is limited storage space. With an Android device you can probably copy to an external drive; but now your carrying even more stuff.

My recommendation - get an 11" MacBook Air with enough disk space for your trip.
Not much bigger or heavier than an iPad; but much more versatile.

Phil.
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Offline reyalp

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Re: Direct Access to external USB HDD for backups
« Reply #8 on: 12 / June / 2013, 23:15:02 »
Quote from: jon.minhinnick on 12 / June / 2013, 22:27:10
Android tablets... hmmm... what about Android phones?
Google android usb otg or android usb host.  Many don't support it out of the box, some can be made to do with with various levels of hacking. One of the things that makes a host different is that it's required to provide power for devices, many phones aren't wired up to do this even if they have a host capable controller.
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what about Winphone (which I have) or IOS (I already have an iPad)?
IOS won't directly, though third party bridge devices as phil described may be an option. Don't know about win phone, but a quick google suggests no.

Another option would be a very small netbook style laptop.
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Offline zeno

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Re: Direct Access to external USB HDD for backups
« Reply #9 on: 15 / June / 2013, 04:00:40 »
You can buy a USB OTG cable for the Nexus 7 tablet on eBay for a couple of pounds/Euros/dollars.

I use that and a small card reader to transfer my photos at end of each day when on holiday.

I'm currently in Italy doing just that.
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