7 inch LCD from a Walmart display.

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7 inch LCD from a Walmart display.

Postby dl_evans » January 19th, 2013, 9:18 am

A friend of mine works at Walmart and gave me this LCD from a torn down display. It has a push button that turns it on, an LED, a speaker, and a pack of 8 D batteries. There is also an SD card slot and a USB slot.

Here are some photos:
https://plus.google.com/photos/10801974 ... 8211592433
dl_evans
 
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Re: 7 inch LCD from a Walmart display.

Postby st2000 » January 22nd, 2013, 8:56 am

You're probably not going to like this, but my bet is that you would be better off picking up known working parts off of ebay and making your own (I assume you want a "computer controlled") picture frame. And if the end game is to have a small computer and/or TV monitor I would definitely start with something more than picture frame hardware.

That said, let's get hacking. I see where someone has purposely masked what type of chip they are using. It might be an AMLogic chip. I've seen them in a number of picture frames. Take a closer look. Remember, someone had to jazz up a lot of these chips and probably didn't do as good as job on some.

But, even if you figure out which chip is driving this thing, you are still at a loss. Custom software could have been used to render a specific viewing experience. At this point I would take a close look at the files on the SDCard. Do back it up first. See if you can find the image files. The 1st hack might be to substitute your own images but use the same name. This, just to see if you can get your own images to display. Then look for some sort of scripting file. It may look like an XML file. If you find this - BINGO! Now you (might) have a way to "script" your own viewing experience. That is, which image to display, in what order and for how long. Look for that sort of stuff.

There are other things you might consider that are somewhat advanced. Here are 3:
1. Check the SDCard for multiple partitions. I doubt you can do this on a Windows box. You will have more luck on a Linux box. It will be like having 2 or more SDCards in one.
2. Plug in any USB ports into a computer and check for either Compound or Complex (i.e. multiple) USB devices. There could be more than 1 device. Like a mass storage device and a controlling device. Again, better chance of seeing this on a Linux computer.
3. Look for a console port. These devices might be running Linux them selves. A console serial port is a staple on such a system. Often it can be exploited especially if the designers do not expect anyone to try.

-good luck
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Re: 7 inch LCD from a Walmart display.

Postby dl_evans » January 24th, 2013, 8:47 pm

I posted this on G+ too and had a conversation with a few people about it.

Here's that link: https://plus.google.com/108019745978944 ... kgv5Jqt6hk

The video file isn't loaded from an SD card it's loaded on some flash somewhere. With an SD card I had laying around plugged in the unit doesn't play or anything. There is a USB port on the side and when I plugged in a thumb drive nothing happens but the unit plays the movie that's been flashed.
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Re: 7 inch LCD from a Walmart display.

Postby st2000 » January 25th, 2013, 9:14 am

Yeah, I read some of those posts. Bottom line is that you really don't know what the OEM has done. You can only make assumptions. Like if the board booted up and found a file of a particular name on the SDCard it would upgrade it's firmware or load in a new movie or load in a new script. You can make other guesses as well. Like it is a magnitude simpler to talk to an SDCard then it is to talk to a USB device. So it is much more likely the SDCard is being looked at then it is the USB port. Or that the bases of the firmware running on the board is Linux mostly because it is free and well documented. On that last point, if it is some sort of Linux, then there is the possibility that there is a consul port. Look for any possible connectors or places where a connector could be soldered in that appears to be a serial port. A dead give away are the silk screen letters such as "TX" & "RX". (Almost) All Unix machines run a console. Gaining access to this and finding the root password (if there even is one) would give you the ability to do just about anything with the device. Providing (big but) there is the code (or you can get the code) to do what you want.

Edit: added later

With an SD card I had laying around plugged in the unit doesn't play or anything.


Ah, that's interesting. So it does behave differently. But it does not display a thing this way? Hum, You know, SDCards formatted in modern Windows machines lack a partition table. The assumption is why bother with one as the SDCard is so small. This results in a real pain when moving from platform to platform. Also, SDCards are accessed byte by byte. But HCSDCards are accessed by (I think) sectors. Something like every address gets back a bunch of bytes on a HCSDCard. So there are two things to try right there. On top of that, you have the problem with names. I would suggest you follow what the guy said over in your other thread and use file names like 001.jpg and 002.jpg. So, I might try to find some old SDCards less then or equal to 2GB and format them on a WindowsXP machine and put files like 001.jpg and 002.jpg on them. I give it about a 1:1000 chance of working. So I wouldn't get too excited over it.

-good luck
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