If you follow the exploits of [Aaron Christophel] (and trust us, you should), you’ll know that for some time now he’s been rather obsessed with electronic price tags, specifically those with e-paper displays. It’s certainly not hard to see why — these low-power devices are perfect for ambient displays, and their integrated wireless capabilities mean you can put one in every room and update them from a central transmitter.
But with such a wide array of products on the market, [Aaron] has found himself doing a lot of e-paper reverse engineering. This involves sticking a logic analyzer between the display and the tag’s microcontroller, which he found to be a rather finicky task. That’s why he created the Universal E-Paper Sniffer: a breakout PCB that lets you snoop on display communication without having to resort to unpleasant methods like scratching off the solder mask to tap into the traces by hand.
It’s a pretty simple gadget: on either side, you’ve got a connector for 24 pin 0.5 mm pitch flat flex cable, which [Aaron] has identified as the most common interface for these displays, and in the middle you’ve got a standard 2.54 mm pitch header. There are no other components on the board, and all the traces go right through to the other side.
Add a few jumpers and a cheap logic analyzer, and you’re ready to sniff some SPI commands. Check out the video after the break for a general walk-through of what it looks like to start sniffing around a new display.
The Gerber files for the breakout are available for free, or you can chose to buy a fabricated board through PCBWay to kick [Aaron] a portion of the sale price. However you get one, we think this will be a handy little tool to have around if you find yourself bitten by the price tag hacking bug.
5 thoughts on “A Handy Breakout Board For E-Paper Hacking”
2.5mm header, that’s a funky spacing for a pinheader.
Round down error
Not really. Both 2.5mm and 5mm mess with you, being so close to the imperial 2.54mm (0.100″) and 5.08mm (0.200″). I can’t speak to how common each pitch is, but I have seen a LOT of different pitches in pin headers, flex cable, screw terminals, and so on. My favourite is 0.156″ vs 4mm.
For two or three contact width, rounding error is a killer. For 8 or 24, the difference is frustratingly clear when you have the wrong one.
I wish someone would do the same for digital micromirror devices…
If I ever come across a box of surplus epaper displays, I’d be interested in getting one of these.
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