[sdiy] Using digital photoframes as a source of cheap graphic LCD screens

[Neil Johnson]

Hi,

Eric Brombaugh wrote:
> Tom Wiltshire wrote:
>> This is synth-diy, but only just, so my apologies if this seems  
>> rather off-topic.
>> I've bought a few LCD character displays for use in my synth  
>> projects (and the first one to use one is now nearing completion)  
>> but I've also wondered about using graphic LCD displays. The  
>> problem with these is the cost.
>> However, digital photo frames are now commonplace and cheap. 7"  
>> frames go on eBay for £20 - try buying a 7" graphic LCD for that  
>> much money!
>> So my question is; Does anyone know of any sites (hackaday or  
>> instructables or such like) that have opened one of these up and  
>> worked out how to interface to it, or does anyone know a good  
>> reason why this isn't a good idea?
>
> Interesting idea. I've seen a few teardowns on these things and  
> there's really not much to them - some sort of big processor/SoC  
> (usually an ARM of some sort, with USB & LCD drive built in), an SD  
> memory slot, power supply and user interface. The biggest problem  
> is that the LCD drive logic is entirely subsumed in the processor,  
> and the processor is mask programmed / OTP so you can't easily  
> reflash it with your own code to take over the display. Another  
> issue is that there are literally thousands of different models/ 
> mfgs of these picture frames out there and there's a lot of churn  
> in the marketplace, so getting a reliable supply of them one you've  
> done the reverse engineering may be a challenge.

You're pretty much on the mark.  Many graphic LCDs use common  
interfaces and protocols - MIPI-DSI, SDI, parallel, proprietary - but  
they operate at high data rates, refreshing the LCD every frame (e.g.  
30fps).  You can get standard micros with built-in LCD drivers  
(VideoCore, OMAP, etc) but then you're rapidly heading into large  
amounts of software.  Assuming, of course, that you can get the  
datasheets for the LCD in the first place to write the driver.

Neil
--
http://www.njohnson.co.uk