OpenDisplay — nRF54 (XIAO nRF54L15)

Bluetooth LE ePaper firmware built with nRF Connect SDK (NCS) + west and bb_epaper.

Channel Sounding / Android ranging is compiled in and enabled at runtime when system_config.device_flags bit 5 (DEVICE_FLAG_CHANNEL_SOUNDING, 0x20) is set in the config packet.

Prerequisites

• nRF Connect SDK v3.0.1+ (tested with v3.3.1)
• Matching toolchain installed via nRF Connect (see ~/ncs/toolchains/)

Build

export NCS_ROOT=~/ncs/v3.3.1   # optional — auto-detected
cd Firmware_NRF54
./build.sh

USB bench debugging (UART serial monitor):

PROFILE=uart ./build.sh

Factory config embed:

FACTORY_CONFIG_HEX='...' ./build.sh

Release versioning:

BUILD_VERSION=v1.2.3 SHA=$(git rev-parse --short HEAD) ./build.sh

Flash

./flash.sh
# or: pyocd flash -t nrf54l build/merged.hex

Battery builds log via SEGGER RTT when a J-Link probe is attached.

Channel Sounding

device_flags bit	Name	Effect
0x20 (bit 5)	DEVICE_FLAG_CHANNEL_SOUNDING	Advertise RAS UUID 0x185B, run CS reflector on connect (pair/bond required for Android ranging)

Default presets leave this bit clear — normal OpenDisplay 0x2446 pipe works without bonding.

For the Seeed XIAO preset (nrf54l15-xiao), set device_flags to 0x21 (0x1 | 0x20).

Android ranging test (e.g. Pixel 10 Pro)

1. Build/flash main firmware with device_flags bit 5 set in the config packet.
2. Pair and bond with the phone when prompted.
3. Expected UART/RTT logs when ranging works:
   • CS capability exchange completed
   • CS config creation complete
   • CS security enabled
   • CS procedures enabled

Default XIAO board DTS uses the onboard ceramic antenna (rfsw_ctl LOW at boot). External IPEX needs P2.05 HIGH — see Seeed zephyr-rfsw example.

References: NCS RAS reflector sample, Nordic Channel Sounding.

nRF54LM20A

NCS v3.3.1 does not yet ship a seeed-xiao-nrf54lm20a board target. LM20 builds remain L15-only until the Seeed board DTS is ported into this tree. Use the Nordic nrf54lm20dk board as a reference for bring-up.

Pin encoding

OpenDisplay configs use compact (port << 4) | pin bytes (e.g. P2.02 → 0x22). Use the nRF54 toolbox presets — do not reuse nRF52840 GPIO numbers.

Layout

• src/ — OpenDisplay application (BLE, protocol, display, optional CS)
• third_party/bb_epaper/ — vendored library with nrf54_zephyr_io.inl
• zephyr/ — CMakeLists.txt, prj.conf, overlays
• build.sh / flash.sh / ncs-env.sh — NCS build helpers