Aaron Christophel's E-Paper Sniffer Breaks Pins Out to Make Electronic Tag Recycling Easier

Designed to make those pesky FPC connectors more amenable to logic analyzers, this passive board breaks out all the pins you need.

Developer Aaron Christophel is continuing his mission to reverse-engineer and re-use ePaper displays from scrapped commercial products, and now has a new tool to share: the Universal E-Paper Sniffer.

"This PCB will help you to very [simply] analyze the SPI communication between an unknown ePaper display [and] the stock microcontroller," Christophel writes of his latest design — an entirely passive board designed to sit between the control board and its display and break out the signals into easily-accessible 2.54mm pin headers.

Fans of discarded electronic price-tags have a new tool to help reverse-engineer their operation. (📹: Aaron Christophel)

"In my last video I showed this small PCB which is an adapter to get SPI data from a microcontroller, like an ESP32 in this example here, into an ePaper display with a more or less standard [controller] pinout," Christophel explains. "The reason I made it is because [of] these ePaper price tags that are now falling from the shelves these days."

Christophel's interest in reusing electronic shelf tags, which use an ePaper display and a small microcontroller to allow pricing and other information to be updated without reprinting physical labels, isn't new: Back in April he showed off a TI CC8051 Flasher tool designed to replace the program running on the stock microcontroller. The Universal E-Paper Sniffer, however, aims to make it easier to figure out exactly what your own program needs to do in order to make the display work again.

"Software-wise, they can be completely different," Christophel says of the tags. "Between them and each display there is [something] different driving over SPI needed to get them to refresh — like you may need to supply a lookup table [and] you need to supply the correct resolution to the display."

By connecting the compact board in between the controller and the display, it's possible to hook up a logic analyzer and sniff the SPI communication to find out how each one is driven — and, from there, write your own software to replace that of the price tag's creator.

A video demonstrating the board in use is available on Christophel's YouTube channel; the board design files have been published to PCBWay under an unspecified license.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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