Xbx nrf

XBX-NRF

A replacement bottom board for the Xbox Series X|S controller (model 1914) built on a Nordic nRF52840. Uses a custom 2.4 GHz USB dongle instead of Xbox Wireless / Bluetooth for improved connectivity.

Status: Hardware Rev 1.1 up and running. Still in active development. Open tasks: todo.md.

Who is this for

This is for those of us who love the Xbox controller's shape but hate how bad the Bluetooth connectivity is. This started as a labor of love for my partner who can't find a controller she likes besides the Xbox controller but also can't stand the disconnects.

That being said, there are some real concessions. The most obvious is that the controller won't work with an Xbox anymore. Another concession is that support for the rechargeable battery packs, as well as the expansion and headphone ports was dropped.

• How to build the hardware: Building the hardware
• Once you have hardware in hand: Getting started

Architecture

┌─────────── Controller ───────────┐          ┌──── Dongle ────┐
│ Stock top board ─J3─ new board   │ 2.4 GHz  │ nRF52840 + USB │
│ buttons (PCAL6416)  nRF52840     │◀────────▶│ XInput / HID   │──▶ PC
│ power latch, boost  radio,       │   ESB    │ gamepad        │
│ USB-C, 2×AA input   sticks,      │          │                │
│                     triggers,    │          │                │
│                     rumble       │          │                │
└──────────────────────────────────┘          └────────────────┘

Features

[!WARNING] Never put a bare Li-ion cell on the AA contacts: The boost converter appears to pass that straight through and the nRF52840 is only rated to 3.6v in this configuration! (docs/hardware.md).

Hardware

The custom board replaces the stock bottom board in the controller. It plugs into the stock top board's 14-pin J3 connector. This provides power rails, USB, I2C to the button expander, and Guide / Pair / power-hold signals.

Firmware

Built using the nRF Connect SDK. Version is pinned at v3.4.1 to ensure future buildability (hopefully). The controller firmware has a target for the custom board and the dongle firmware has a target for the custom dongle as well as the PCA10059 dongle. You may notice there is a nice!nano/pro-micro target for the controller, but this is just for testing.

Configurator

Desktop app for settings, calibration, input and rumble tests and firmware updates of both devices over USB using Python + Tkinter. So far only tested on Linux, but in theory should be buildable on Mac and Windows.

• Getting started: docs/getting_started.md
• Details: docs/configurator.md

Repository layout

docs/                documentation
firmware/
  boards/            our board definitions (xbx_controller, xbx_dongle)
  bootloader/        UF2 bootloader build (upstream + our boards)
  common/            shared code (include/protocol.h)
  xbx-nrf/           controller app
  dongle/            dongle app
  ncs-version        pinned SDK + toolchain
  check-sdk.sh       version check for build.sh
  build.sh           build (+ flash) script
pcb/xbx-nrf/         KiCad project, controller board (lib/: symbols,
                     footprints, 3D)
pcb/xbx-nrf-dongle/  KiCad project, dongle board
mech/                FreeCAD parts: controller-bottom-board/ (board outline),
                     dongle-enclosure/, aux-button-guide/ (CC BY-NC-SA remix)
references/          schematics, scans, datasheets, pinouts
tools/               configurator/, release scripts (pcb-release.sh,
                     release-notices.sh), test-rumble.sh
todo.md              task list

Disclosures

This was built with the help of Claude Code. PCB designs are completely hand designed by myself, and all code was either written or reviewed by myself. However, there are likely still bugs present as this is a hobbyist project in early development. PCB designs may also have flaws for the same reasons. If you find and bugs or issues with the hardware, please open an issue to let me know.

References

• Schematics, scans, pinouts and datasheets: references/README.md (third-party, not in the repo; source links there)
• AcidMods — XB1 controller PCB scans
• GP2040-CE (XInput reference)

License

Copyright (c) 2026 zuidec. Firmware and scripts: MPL-2.0. Hardware design: CERN-OHL-S-2.0. Documentation: CC-BY-4.0. Third-party CAD parts (SnapMagic, KiCad libraries) keep their CC-BY-SA-4.0 licenses; see the ATTRIBUTION.md in each library folder. Details: LICENSE, REUSE.toml, full texts in LICENSES/.