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I have a Transcend [TS-PF705B] digital photo frame lying around with me for a while. And since the day i got this unit, i always gave a thought to do some thing with, like hooking it up with my Raspberry Pi.

I tool them apart and found 2 major IC inside.. backside of the LCD at the left and the PCB on the right

here is a bit closer look (Sorry for the image if not that clear,.. I dont have a better camera) PCB

IC's:

  • K4S281632K-UC75[SAMSUNG 034]: which is a 128Mb SDRAM
  • AM7338 [BB90KAA A14]: Couldn’t get any information.

This is my first time to do some reverse engineer at this level, and im learning things really slow.

Mean while i had a question, whether by any means is it possible to connect a Raspberry pi's RF video out to this LCD or Is this Display is meant only for displaying still images.

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  • Your best bet is to het the datasheet of the LCD display. I doubt that uou could interface that with a RPi for moving images though. Also questions like this (very specific to a piece of hardware, I mean the phooto frame) are bound to be closed as they are of little interest to anyone else. – FakeMoustache Dec 31 '15 at 14:46
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    That's a bit naughty of the EESE guys IMHO - you only said you thought you might hook it up to a RPi! 8-) – SlySven Dec 31 '15 at 21:12
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    @slysven one mod there will instantly close and migrate at the drop of a pin if it mentions rpi, arduino, etc, regardless what the question is. – cde Dec 31 '15 at 23:28
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The manual on the Trancend Website (see pjc50's answer) suggests that the unit will be recognised by a PC if a USB lead is connected to the mini-USB connector (C) on the SIDE of the case (not the full size one on the back). It says that a Linux kernel 2.4 or greater is required then any memory card inserted in the unit will appear for the PC to access (and it will appear as a Mass Storage device)...

Whilst this is not perhaps as much hackery as you were hoping for, I think you could still upload a single or more images to an insert card and it would displayed - but whether that would happen whilst the PC or (since Linux 2.4 kernels are ancient history as RPis are now using 3.x or 4.x kernels) even a Raspberry Pi should be able to do that. Whilst there is little gain for doing this with existing static images there is nothing to stop the Pi from creating suitable images - with say weather or news reports, and pushing them to the frame every few minutes, for instance...

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    In my experience, it won't display anything when in usb slave mode. It wouldn't be good to dual mount the flash, data corruption. – cde Dec 31 '15 at 23:30
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    Or that is to say, it will display "usb connected", not a picture. The usb slave mode is just to allow access to the internal flash. – cde Jan 1 '16 at 5:29
  • That's a pity - it must switch to behaving like a hub/card reader-writer when it detects a Host using the mini USB... – SlySven Jan 1 '16 at 20:07
  • @cde Ah, can the RPi shut-down the USB port between writes - then the device will think it is disconnected and revert to "displaying a picture" mode...? – SlySven Jan 7 '16 at 19:55
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    I don't believe the rpi has that type of control – cde Jan 7 '16 at 22:03
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The AM7338 is a dedicated Digital Picture Frame System on Chip (DFP SOC). It is a all in one single chip solution for DFPs, handling typical functions of buttons, IR remote, memory card and flash reading, USB host and slave, and most important, direct LVDS display interfacing.

It is in the same family as other AM733x chips, and they all use the same general reference design. See ftp://relay.alkotel.ru/service/DPF/TF-101/Diagrams/teXet_TF-101_AM7331.PDF (Warning: PDF Autodownload) for a full schematic breakdown of a similar AM7331 DFP. Notice the display LVDS connections.

There is slim to little chance of reverse engineering this unless you already know how. You cannot hack the board to accept Composite or dvi/hdmi. You could attempt to interface with the display directly though.

Some DFPs did use multiple boards that could easily be hacked. One I have, years ago, used a generic VGA to LVDS board. I disconnected the DFP board and added a VGA connector, though it allowed composite as well. That's an old, inefficient design, much like older huge dvd players.

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That's a lot of RAM, so I suspect the board is already running Linux or some other embedded OS on that unidentified AM7338 chip. You may be lucky and one of the two connectors on the top edge (U8, J11) is either a UART or a JTAG/SWD connector.

(The firmware is available for download: http://www.transcend-info.com/Support/No-311 )

Edit: the firmware has helped me determine it's an Action Semiconductor device, but not one listed on their website. It contains some 8.3 filenames and UTF16 strings, so I think it might actually be running Windows CE.

The other approach would be to look at the LCD itself and see if it's compatible with the Pi's output: you might, if you're very lucky, be able to plug it straight into the FFC connector on the Pi, power up its backlight, and be done. This leaves the original circuit board out entirely.

  • You will need to confirm that the display's connector IS indeed FFC (see datasheet), if it is not you might damage your RPi. – FakeMoustache Dec 31 '15 at 14:47
  • Yes, should have clarified: you need to look up the LCD's datasheet and pinout. – pjc50 Dec 31 '15 at 14:48

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