Kai Pereira's Ticket-Shaped Raspberry Pi RP2040-Powered Badge Boasts a "Zero-Power" Design

18-year-old maker Kai Pereira has designed a Raspberry Pi RP2040-powered near-field communication (NFC)-capable badge with an ePaper screen, for a high-school game jam event in Singapore — and it needs "zero power" for its primary functions.

"These badges needed to be really cheap and simple, because we were going to manufacture about a hundred in a pretty limited amount of time," Pereira explains of the thinking that went into the badge's design. "I went with a zero-power approach, which means sticking with [ePaper displays], and I decided to include NFC if the organizers wanted to introduce it into the roleplay of the event, and so participants could add their website or GitHub if they so choose!"

The finished badge is driven by a Raspberry Pi RP2040 microcontroller with 4MB of flahs storage, and includes a USB Type-C connection for power and data — but a dedicated power supply isn't strictly necessary for "core features." The trick there is twofold: the display is an electrophoretic ePaper panel, which requires power only when changing state and retains whatever it was last displaying even when unpowered; and the Near-Field Communication (NFC) side can operate passively thanks to an STMicroelectronics ST25 chip.

While that covers the two key functions, adding power opens up a lot of other possibilities. 20 general-purpose input/output (GPIO) pins are brought out from the microcontroller to unpopulated pin headers for easy expansion with external hardware, and the NFC side of the ticket-shaped badge can be flipped from passive into active mode "if you want to do some more complicated stuff," its creator explains.

"The boards are really easy to get manufactured if you'd like to have some of your own," Pereira says. "They're much cheaper to order in bulk, at about less than $5/board and another $5 for the [ePaper panel], but getting at MOQ [Minimum Order Quantity] will cost about $100 for five with PCBA [Printed Circuit Board Assembly] (hand soldering is probably significantly cheaper though). The board is really easy to setup! Just plug it into your computer via USB-C, drop in the [Raspberry] Pi Pico MicroPython bootloader and then upload the firmware using Thonny to the devboard!"

The badge's design files and firmware source code are available on GitHub under an unspecified open-source license, along with a "retroactive journal" of its design; more information is available in Pereira's Reddit post.