Following its exploitation [Aaron Christophel] (And trust us, you should), you may find that for some time he has been obsessed with electronic price tags, especially e-paper displays. It’s not hard to see why – these low-power devices are perfect for ambient display, and their integrated wireless capabilities mean you can have one in each room and update them from a central transmitter.
But with such a wide range of products on the market, [Aaron] I have seen myself doing a lot of e-paper reverse engineering. This involves sticking a logic analyzer between the display and the tag’s microcontroller, which he thinks is a rather tricky task. That’s why he created Universal E-Paper Sniffer: a breakout PCB that lets you snoop on display communication without resorting to unpleasant methods, such as scratching the solder mask to tap on traces by hand.
This is a very common gadget: on both sides, you get a connector for 24 pin 0.5mm pitch flat flex wire, which [Aaron] Marked as the most common interface for these displays, and in the middle you get a standard 2.5mm pitch header. There are no other elements on the board, and all traces go to the other side on the right.
Add a few jumpers and a cheap logic analyzer and you’re ready to sniff some SPI commands. Watch the video after a break for a simple walk to see what it feels like to start sniffing around a new display.
Garbage files for breakout are available for free, or you can choose to buy a fabricated board through PCBO [Aaron] A fraction of the sale price. However you get one, we think it would be a simple little tool if you keep biting yourself by the price tag hacking bug.