The CoffeeCaller nRF52840 board is the sort of project that makes more sense the longer you look at it. It takes the board takes Nordic Semiconductor’s multiprotocol SoC and wraps it in a maker-friendly layout with real-world peripherals already on the PCB. For readers brushing up on the CAD side, this KiCad primer is still a handy refresher before diving into the files.

What Makes the CoffeeCaller nRF52840 Board Interesting?

According to the public repository, the hardware centers on a 64 MHz Arm Cortex-M4-based nRF52840 with 1 MB of flash, 256 KB of RAM, USB-C power input, and a 3.3 V LDO rated for 200 mA. Around that are five buttons, four GPIO LEDs, four WS2812 RGB LEDs, a PWM buzzer, an SHT40 temperature-and-humidity sensor, Qwiic, NFC connectivity, a 10-pin SWD header, four servo-style headers, and a 16-pin female header exposing free GPIO and power rails. In other words, this is not just a radio breakout with a marketing adjective glued to it.

CoffeeCaller 3D Render
A 3D rendering of the open-hardware CoffeeCaller board based on Nordic’s nRF52840 wireless SoC. Image: CoffeeCaller 3D rendering, © 2025 Andreas Kurz, from the CoffeeCaller repository, licensed under CERN-OHL-S-2.0+.

The more useful part for many readers is that the CoffeeCaller nRF52840 board is not presented as a black box. The repository includes KiCad project files, schematic and PCB sources, a PDF schematic, and a CERN-OHL-S-2.0 license. The readme also points builders to an EasyEDA-to-KiCad component-import flow and to JLCPCB production-file generation, which tells you this was meant to be built, modified, and manufactured, not merely admired in a screenshot.

The CoffeeCaller nRF52840 Board in Practice

There is also already a software story around it. The board appears in public board documentation for Bridle, which builds on Zephyr and lists support for GPIO, I2C, PWM, USB device mode, WS2812 control, watchdog functions, and IEEE 802.15.4 radio features. That matters because a nice-looking PCB is one thing; a board definition that lets you start compiling and testing code without inventing everything from scratch is another. If wireless development is your angle, Elektor’s look at BLE sniffing with an nRF52840 dongle fits neatly beside this project.

It is not a polished commercial platform yet, and that is part of the charm. Some of the Bridle documentation still contains TODO markers for positions and pinouts, so expect a little archaeology. Even so, for engineers, students, and makers who want to study how a compact open-hardware nRF52840 board is put together, CoffeeCaller looks like a solid starting point and a refreshingly inspectable one.