nrf54-arduino-core

nRF54L Arduino Core

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Native PlatformIO Support

Build, upload, monitor and debug all six board targets directly from PlatformIO.

Use the same Arduino API, bundled BLE libraries and board options in VS Code or from the command line. Native support includes GDB debugging, Unity tests and ELF/HEX/BIN/UF2 output, without requiring Arduino IDE or Arduino CLI.

Start with the PlatformIO tutorial below · Complete PlatformIO guide · Blink example · BLE UART example

PlatformIO support is included in 1.0.21 and later, with separate Arduino and PlatformIO release packages. The tutorial below pins the Git installation to v1.0.23; use #main when following ongoing development.

Project Scope

The 1.0.x line focuses on a dependable Arduino, peripheral, power-management, and Bluetooth LE experience on supported nRF54L boards. The core is suitable for real BLE prototyping and embedded applications within the documented single-link security/privacy scope. Release-critical feature probes are compiled from the exact packaged archive, the source checkout receives broader example coverage, and the release gate compiles representative targets for both a XIAO nRF54L15 and a XIAO nRF54LM20A.

The following protocol work is included for evaluation, but is not finished or production-ready:

Area	Current boundary
Zigbee	Experimental partial stack and device demonstrations; incomplete Zigbee PRO coverage, routing, clusters, OTA, and ecosystem interoperability
Thread	Staged OpenThread FTD/MeshCoP/SRP/UDP with settings recovery, commissioner/joiner, sleepy-child, and mixed-board test paths; certification and broader interoperability remain
Matter	Staged system, crypto, packet-buffer, IPv6/UDP, ACL, onboarding, and custom PASE/CASE demo work; not an upstream wire-compatible or certifiable Matter device stack
Channel Sounding	Experimental two-board controller-backed LE CS Test; not connected-ACL Channel Sounding, calibrated ranging, cross-vendor interoperability, or a qualification claim

The Thread and Matter entries describe the experimental platform work included in 1.0.8; those menu targets remain explicitly outside the stable feature claim.

These boundaries keep the stable claims precise: unfinished protocol examples are useful engineering work, but they are not presented as complete standards implementations.

Why Use This Core?

Capability	Practical benefit
Arduino workflow	Install from Boards Manager, select a board, compile normal .ino sketches, and upload over a connected CMSIS-DAP probe
Native PlatformIO	Build all six board targets, use bundled and registry libraries, upload, monitor serial, run Unity tests, and debug with GDB without Arduino IDE or CLI; see the quick start
No Zephyr runtime	Shorter build cycles, smaller applications, and fewer framework layers between a sketch and the hardware
Direct peripheral access	GPIO, ADC, PWM, serial buses, audio, NFC, DPPI, GRTC, watchdog, comparators, and power controls are implemented against nRF54L hardware
Useful BLE depth	Peripheral, central, dual-role, GATT server/client, HID, BLE UART, PHY/DLE/MTU control, LE Secure Connections, bonding, OOB, Numeric Comparison, privacy/RPA, and CSRK signed writes
Low-power board integration	System ON idle, timed System OFF, reset-cause APIs, XIAO RF-switch control, LM20A external-flash power-down, and nPM1300 hibernate support
Dual-core access	Use the 128 MHz Cortex-M33 application CPU and the VPR RISC-V coprocessor without adopting a vendor RTOS
Observable validation	Public diagnostics, regression scripts, release-archive compilation, and a repeatable two-board hardware gate document what was actually tested
Cross-board build isolation	L15 and LM20A objects carry linker-checked SoC identities, and Arduino automatically clears stale objects when the selected board or installed platform changes

This core is a good fit when Arduino productivity and close control over timing, memory, radio behavior, or power matter more than adopting the full nRF Connect SDK application model. For a product that requires a Bluetooth, Matter, Thread, or Zigbee qualification program, treat this core as engineering source and validate the complete product against the relevant conformance suite.

Contents

• PlatformIO quick start
• Quick install
• Getting started
• Supported boards
• Feature matrix
• Bluetooth LE
• Power consumption
• SPI and QSPI
• System OFF and PMIC APIs
• Maturity and limitations
• Troubleshooting
• License

PlatformIO Quick Start

1. Install PlatformIO And Git

Install PlatformIO IDE for VS Code or PlatformIO Core 6.1.18 or newer, plus Git.

On Windows, enable Developer Mode in Windows settings, then run this once before the first build so Git preserves the core’s linked headers:

git config --global core.symlinks true

2. Create A Project

Open a new project folder in VS Code. It needs these two files:

my-nrf54-project/
  platformio.ini
  src/
    main.cpp

Use this platformio.ini for a XIAO nRF54L15 / Sense:

[env:xiao]
platform = https://github.com/lolren/nrf54-arduino-core.git#v1.0.23
board = xiao_nrf54l15
framework = arduino
upload_protocol = pyocd
monitor_speed = 115200

For a XIAO nRF54LM20A / Sense, change just the board line:

board = xiao_nrf54lm20b

The historical lm20b board ID selects the LM20A hardware and memory layout. The full board list and options cover HOLYIOT, generic modules and the Nordic DK too.

3. Add Your First Sketch

Put this in src/main.cpp:

#include <Arduino.h>

void setup() {
  Serial.begin(115200);
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_BUILTIN, LOW);
  delay(500);
  digitalWrite(LED_BUILTIN, HIGH);
  Serial.print("Uptime (ms): ");
  Serial.println(millis());
  delay(500);
}

4. Build, Upload And Monitor

Connect one board over USB and run these commands from your project folder:

pio run
pio run -t upload
pio device monitor

The first build downloads the core and its compiler automatically. The pyOCD upload helper installs its pinned Python dependencies when needed. The serial monitor should print an increasing uptime about once per second; press Ctrl+C to exit it. In VS Code, the PlatformIO Build, Upload and Serial Monitor actions run the same workflow.

For multiple connected boards, select the upload probe with board_upload.uid and the serial device with monitor_port; see upload and serial configuration.

The repository includes ready-to-run Blink and BLE UART projects. The BLE example advertises as X54-PIO; attach the LM20A antenna before radio testing. See the complete guide for third-party libraries, 128 MHz operation, debugging, Unity tests and validation limits. Pin the Git URL to a specific commit or release tag when you need a reproducible project.

Quick Install

https://raw.githubusercontent.com/lolren/nrf54-arduino-core/main/package_nrf54l15clean_index.json

Add this URL in Arduino IDE → Preferences → Additional Boards Manager URLs, then install nRF54L15 Boards from the Boards Manager.

Normal uploads use the bundled native nRF OCD tool on Linux and Windows, so Windows does not need a separate Python install just to upload. If native upload fails, switch Tools -> Upload Method to pyOCD Recovery; its first setup installs pinned dependencies into the packaged tool-local runtime and requires access to the configured Python package index. J-Link via pyOCD (Experimental) is also available after installing SEGGER’s official J-Link driver package; this path has software-only coverage and still needs user hardware validation.

Arduino CLI Install And Updates

Arduino IDE users can update through Tools -> Board -> Boards Manager by searching for nRF54L15 Boards and clicking Update when a newer release is available.

Linux/macOS:

BOARD_URL="https://raw.githubusercontent.com/lolren/nrf54-arduino-core/main/package_nrf54l15clean_index.json"

arduino-cli config add board_manager.additional_urls "$BOARD_URL"
arduino-cli core update-index
arduino-cli core install nrf54l15clean:nrf54l15clean

# Check whether this core has an available update.
arduino-cli core list --updatable

# Update this core to the latest Board Manager release.
arduino-cli core upgrade nrf54l15clean:nrf54l15clean

Windows PowerShell:

$BoardUrl = "https://raw.githubusercontent.com/lolren/nrf54-arduino-core/main/package_nrf54l15clean_index.json"

arduino-cli config add board_manager.additional_urls $BoardUrl
arduino-cli core update-index
arduino-cli core install nrf54l15clean:nrf54l15clean

# Check whether this core has an available update.
arduino-cli core list --updatable

# Update this core to the latest Board Manager release.
arduino-cli core upgrade nrf54l15clean:nrf54l15clean

arduino-cli outdated is also useful when you want to see all updatable cores and libraries. If core list --updatable prints nothing for nrf54l15clean:nrf54l15clean, the installed core is already current.

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Getting Started

Arduino IDE

1. Install the package with the Boards Manager URL above.
2. Connect the board and select Tools -> Board -> nRF54L15 Boards, then choose XIAO nRF54L15 / Sense or XIAO nRF54LM20A / Sense.
3. Keep CPU Frequency -> 64 MHz for normal sketches. Use 128 MHz only when an example explicitly requires it, including the Channel Sounding pair.
4. Start with one of the examples below and click Upload. The default native nRF OCD uploader selects the connected CMSIS-DAP probe; the recovery uploader is available from Tools -> Upload Method. Select J-Link via pyOCD (Experimental) only when using an onboard or standalone SEGGER J-Link.
5. Open the Serial Monitor at the baud rate selected by the sketch. If serial output is missing, verify Tools -> Serial Routing and close other programs that own the port.

On the XIAO nRF54L15, the default USB bridge when powered route keeps the SAMD11 bridge pins high-impedance until the host opens the serial bridge. This allows BLE sketches to boot safely from battery; choose Header UART when a physical D6/D7 UART is required.

Recommended first examples:

Goal	Arduino example
Verify the board and core	Nrf54L15-Clean-Implementation > Diagnostics > CleanBringUp
Create a phone-visible BLE UART peripheral	Bluefruit52Lib > Peripheral > bleuart
Scan and connect as a BLE central	Bluefruit52Lib > Central > central_bleuart
Exercise authenticated pairing	Bluefruit52Lib > Security > pairing_numeric_comparison
Enter and recover from timed System OFF	Nrf54L15-Clean-Implementation > LowPower > LowPowerGrtcPwmSystemOff
Inspect LM20A external flash	nRF54 Board Examples > XIAO-nRF54LM20A > QspiFlashInfo
Read the LM20A Sense microphone	nRF54 Board Examples > XIAO-nRF54LM20A-Sense > XiaoLM20A_MicLevel

Hardware-specific sketches are grouped under File > Examples > nRF54 Board Examples. The XIAO-nRF54L15-Sense and XIAO-nRF54LM20A-Sense submenus contain the matching onboard IMU and microphone sketches; base-board flash, RGB, and control examples remain in their XIAO submenu, while HOLYIOT-25008 and the Nordic nRF54L15 DK have separate submenus.

Arduino CLI

The board identifiers deliberately retain the original internal LM20B name for package compatibility:

# XIAO nRF54L15 / Sense
arduino-cli compile \
  --fqbn "nrf54l15clean:nrf54l15clean:xiao_nrf54l15" \
  "$HOME/Arduino/MySketch"

# XIAO nRF54LM20A / Sense
arduino-cli compile \
  --fqbn "nrf54l15clean:nrf54l15clean:xiao_nrf54lm20b" \
  "$HOME/Arduino/MySketch"

# The core can identify a single attached probe automatically.
arduino-cli upload \
  --fqbn "nrf54l15clean:nrf54l15clean:xiao_nrf54l15" \
  "$HOME/Arduino/MySketch"

When two boards are attached, select the target explicitly with the port or UID reported by arduino-cli board list or pyocd list. Disable experimental Thread, Matter, or Zigbee build options unless the sketch actually uses them; this reduces compile/link surface and makes the intended runtime clear.

Experimental J-Link upload

Install the official SEGGER J-Link Software and Documentation Pack first, reconnect the debugger, and confirm that pyocd list --probes reports a J-Link. Then select Tools -> Upload Method -> J-Link via pyOCD (Experimental). The Nordic nRF54L15 DK’s onboard J-Link and a standalone J-Link are both intended to work.

If a standalone J-Link does not expose a serial/VCOM port, select Tools -> Programmer -> J-Link via pyOCD (Experimental) and use Sketch -> Upload Using Programmer. This programmer route does not require a fabricated serial port. The equivalent CLI invocation is:

arduino-cli upload -b nrf54l15clean:nrf54l15clean:nrf54l15dk_pca10156 \
  -P jlink /path/to/sketch

When multiple J-Links are connected, set NRF54L15_JLINK_UID to the intended SEGGER serial number. The uploader refuses interactive or cross-transport auto-selection in that situation.

This mode restricts pyOCD discovery to the J-Link plug-in, leaves target-power control disabled, and does not fall back to another attached debug probe. It uses pyOCD’s nRF54 target support rather than adding the proprietary J-Link transport to open-nrf-ocd. It has not yet been flashed on maintainer J-Link hardware, so please report the J-Link model, operating system, and complete upload output if it fails.

Sketch Compatibility

Normal Arduino APIs such as pinMode, digitalWrite, analogRead, analogWrite, Wire, SPI, and Serial are available. BLE sketches should use the bundled Bluefruit52Lib compatibility API or the lower-level clean-core BLE interfaces shown in the packaged examples. ArduinoBLE is not the native BLE library for this core.

Board-specific hardware still matters. The Sense IMU is on Wire1; the LM20A external header SPI and onboard QSPI flash use different controllers; and the L15 antenna selection controls an external RF switch. Consult the board reference before using fixed-function pins or direct register access.

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Current BLE Highlights

• LE Secure Connections security now includes asynchronous Numeric Comparison accept/reject handling, request-scoped keyboard/passkey input, explicit bonding/MITM/SC/key-size policy, and OOB records supplied mutually or in either one-way direction.
• SMP security now reduces encryption keys to the negotiated 7-16 octet size, enforces the 30-second transaction timeout with single-peer repeated-attempt throttling, and aborts without deterministic fallback if CRACEN entropy is unavailable.
• BLE privacy now keeps the stable local identity separate from the active RPA, derives the local IRK from the identity root, distributes identity keys during bonding, resolves bonded peers through hardware AAR, and reuses the retained bond after an RPA change.
• SMP can exchange and retain CSRKs for both roles. ATT Signed Write Commands use AES-CMAC signatures, monotonically persisted counters, replay rejection, and a Bluefruit client writeSigned() entry point.
• Bond storage now retains up to eight peers with power-loss-safe replicated records, per-peer CCCDs and Service Changed state, role-correct legacy key tuples, LRU replacement, indexed inspection/deletion, and RPA resolution.
• GATT Robust Caching includes a spec-generated 128-bit Database Hash, persistent per-bond Client Supported Features, Database Out Of Sync handling, change-aware transitions, and notification/indication suppression while a client cache is stale.
• Bluefruit central support now includes safe service/characteristic object lifetimes, handle-range discovery, bulk characteristic discovery, readCharByUuid(), central indications, and bonded reconnect encryption.
• Custom GATT characteristics now enforce fixed and maximum lengths for local updates, remote writes, and prepare/execute writes. Service permissions are inherited by their characteristics. Dynamic read/write authorization runs callbacks outside the radio ISR, supports approve, reject, and replacement values, and fails closed on timeout or disconnect. Battery Service database writes and explicit notifications now have distinct behavior.
• BLEUart::bufferTXD(true) now coalesces small writes into the current ATT notification payload, sends a full packet automatically, and lets sketches explicitly flush a partial packet without discarding it on backpressure.
• Bluefruit central reads continue with Read Blob requests across ATT fragments, characteristic discovery determines complete handle ranges, and the HID client selects generic reports through their Report Reference descriptors.
• ATT responses and callbacks now act only on fresh link-layer packets, and service, characteristic, descriptor, and Read Blob pagination rejects malformed lengths, out-of-range handles, and non-advancing peer responses.
• Connection setup now rejects malformed access addresses, timing, channel-map, window, and hop fields before changing live state. Accepted central-side LL and L2CAP connection-parameter requests proceed to a scheduled connection update, and reserved SMP fields are rejected.
• Locally initiated connections now derive their access address and CRC seed from fail-closed hardware entropy before radio ownership changes, including the additional transition constraints required by LE Coded PHY.
• The ANCS client now sends complete notification/app attribute commands, reassembles fragmented Data Source responses, and implements title, subtitle, message, app-name, message-size, date, action-label, and action APIs. Fragmented response parsing is covered by host-side regression tests; live iOS behavior still depends on the phone’s ANCS permissions and interoperability.
• The full two-board release gate exercises positive and rejected Numeric Comparison, all three OOB directions, RPA rotation, identity-key distribution, privacy-aware bonded reconnects, and signed-write counter persistence/replay rejection on XIAO nRF54L15 and XIAO nRF54LM20A.
• Timed System OFF now verifies reset-reason clearing before entry and exposes an abort-stage diagnostic; the gate requires two consecutive GRTC wake-reset cycles after the deliberate reset boundary on each connected board.
• XIAO nRF54LM20A Sense PDM uses the product-specific EDGE/RATIO encodings and a 1.28 MHz clock for 16 kHz PCM. The driver uses byte-addressed EasyDMA, re-arms LM20 clock/filter configuration after STOP, fences DMA ownership at STOPPED, and invalidates stale cache lines before samples are read. A final simultaneous 70-second hardware soak completed 115/115 captures on each Sense board with no timeout, underfill, guard, or DMA error: L15 captures took 503-505 ms and LM20A captures 504-505 ms. Live peak-to-peak response reached 4,626 counts on L15 and 3,994 counts on LM20A.
• Arduino IDE examples are grouped by board and Sense hardware. LM20A flash and RGB sketches, both XIAO Sense IMU/microphone sets, HOLYIOT-25008, and the Nordic DK now have distinct menus, with duplicate platform sketches removed.

Install the stable release from the normal Boards Manager feed shown above, or request the exact version with Arduino CLI:

arduino-cli core install "nrf54l15clean:[email protected]"

• Controller-backed Bluetooth LE Channel Sounding Test is now available through the two public Arduino examples: BleChannelSoundingInitiator and BleChannelSoundingReflector.
• Nordic SDC/MPSL runs the timing-critical LE CS Test. The examples establish a per-cycle session token before the test and verify that same token when the reflector returns its controller result, so delayed results are not paired with a new sounding cycle.
• The public pair is hardware-validated with XIAO nRF54L15 and XIAO nRF54LM20A in both initiator and reflector roles. It requires the 128 MHz CPU profile.

This is an experimental two-board LE CS Test path, not a connected-ACL Channel Sounding implementation or a Bluetooth qualification claim. See the Channel Sounding status for the protocol boundary, measurements, and validation evidence.

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Supported Boards

Product	Arduino board selection	Specs / notes
Seeed Studio XIAO nRF54L15	XIAO nRF54L15 / Sense (xiao_nrf54l15)	128 MHz M33 + 128 MHz RISC-V coprocessor · 1.5 MB NVM · 256 KB RAM
Seeed Studio XIAO nRF54L15 Sense	XIAO nRF54L15 / Sense (xiao_nrf54l15)	Same core board support as XIAO nRF54L15 · onboard LSM6DS3TR-C IMU + MSM261DGT006 PDM mic
Seeed Studio XIAO nRF54LM20A	XIAO nRF54LM20A / Sense (xiao_nrf54lm20b)	128 MHz M33 + 128 MHz RISC-V coprocessor · 2 MB NVM · 512 KB RAM · nPM1300 PMIC · onboard 8 MB PY25Q64 QSPI flash · back pinout
Seeed Studio XIAO nRF54LM20A Sense	XIAO nRF54LM20A / Sense (xiao_nrf54lm20b)	Same core board support as XIAO nRF54LM20A · onboard LSM6DS3TR-C IMU + MSM261DGT006 PDM mic · nPM1300 PMIC · onboard 8 MB PY25Q64 QSPI flash · back pinout
HOLYIOT-25007	HOLYIOT-25007 nRF54L15 Module (holyiot_25007_nrf54l15)	18.0 x 14.8 mm · PCB antenna
HOLYIOT-25008	HOLYIOT-25008 nRF54L15 Module (holyiot_25008_nrf54l15)	23.2 x 17.5 mm · PCB antenna
Generic nRF54L15 36-pad module	Generic nRF54L15 Module (36-pad) (generic_nrf54l15_module_36pin)	Reference module target; verify the power, clock, antenna, and pin design of the carrier board
Nordic nRF54L15 DK	Nordic PCA10156 nRF54L15 DK (nrf54l15dk_pca10156)	Development-kit target for bring-up and peripheral testing

See board reference for detailed pin assignments and schematics.

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Why Bare Metal?

	This Core	nRF Connect SDK
RTOS	None (opt-in Thread/Matter)	Zephyr RTOS mandatory
Binary size	~12 KB blink	~100 KB+ blink
Compiler	GCC	GCC + Zephyr build system
Peripheral access	Direct register writes	Vendor HAL + DTS
BLE stack	Custom register-level; bundled Nordic SDC/MPSL for Channel Sounding	SoftDevice / Zephyr BLE
RISC‑V coprocessor	Direct boot/control and offload access; general runtime remains partial	Limited Arduino access
Learning curve	Datasheet + Arduino API	Zephyr + DTS + Kconfig

This core is for developers who want full hardware control with Arduino convenience.

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Feature Matrix

This matrix describes the current main branch. The Boards Manager release can lag behind it. A feature is not marked complete merely because a header, constant, codec, or demonstration exists. The tables enumerate public protocol families and major user-facing capabilities; related optional specification procedures are grouped instead of pretending that every standards clause is a separate feature.

Status	Meaning
Implemented	Available through a supported API and exercised within the boundary stated in the row. This does not imply standards certification.
Partial	A useful subset works, but important behavior, roles, or interoperability are missing.
Experimental	Evaluation code and examples exist; APIs or behavior may change and production use is not claimed.
Missing	No supported standards-compatible implementation is provided. A stub or private test protocol may still exist.
Hardware boundary	The nRF54L device or supported board does not expose the required hardware.

Protocol Inventory

Protocol or interface	Status	What users get
Bluetooth Low Energy	Implemented	Practical single-active-link central/peripheral operation, GAP, ATT/GATT, common services, security, bonding, privacy, HID, NUS, PHY/DLE/MTU control, and Bluefruit-compatible APIs. It is not a qualified complete Bluetooth controller.
Bluetooth LE extended advertising/scanning	Partial	Local extended payload transmission and scanner reassembly through 995 bytes; broad cross-vendor and connectable-extended interoperability remain open.
Bluetooth LE Channel Sounding	Experimental	Standalone two-board, single-antenna controller-backed LE CS Test. No connected-ACL ranging or cross-vendor claim.
Bluetooth Mesh	Missing	No Bluetooth Mesh provisioning, bearer, transport, model or relay stack is shipped.
IEEE 802.15.4	Partial	2.4 GHz PHY, TX/RX, CCA/ED, filtering, ACK and frame-pending primitives. A complete reusable MAC transaction engine is missing.
Proprietary raw 2.4 GHz radio	Implemented	Raw packet TX/RX and acknowledgement examples for direct radio experimentation.
Zigbee	Experimental	Direct-device examples, secure join/rejoin pieces, selected ZDO/ZCL paths, sleepy examples, and Zigbee2MQTT integration. It is not a complete Zigbee PRO stack.
Thread	Experimental	A real imported OpenThread FTD core with an nRF54 platform port, local two-board UDP and MeshCoP validation, and staged SRP/sleepy-device paths.
Matter over Thread	Experimental	CHIP system, crypto, packet-buffer and Inet foundations plus private onboarding/session demos. There is no standards-compatible Matter device runtime yet.
NFC-A tag	Partial	NFCT sense, activation, frame and EasyDMA APIs plus a tag setup example; antenna and phone interoperability depend on the board design and remain lightly validated.
UART/UARTE	Implemented	Serial, Serial1, routing options, buffered I/O, and lower-level UARTE access.
I2C/TWI	Partial	Wire, Wire1, repeated starts and controller mode are established; TWIS target APIs exist with narrower multi-instance validation.
SPI	Partial	Arduino SPI, lower-level SPIM, board-specific high-speed paths, and SPIS target examples.
I2S, TDM, and PDM audio	Partial	I2S TX/RX/duplex on nRF54L15 and PDM capture on supported Sense boards. nRF54LM20A uses TDM instead of I2S, and no TDM wrapper is exposed yet.
External QSPI flash	Implemented	LM20A onboard PY25Q64 access through SPI_HS, Adafruit SPIFlash compatibility, and explicit deep-power-down support.
VPR IPC/RPC	Partial	RISC-V boot/control, shared transport and selected offload/service probes; not a general production softperipheral runtime.
CMSIS-DAP/SWD upload transport	Implemented	Packaged native nRF OCD upload with pyOCD recovery and UID-bound two-board validation tooling.
Native USB device / TinyUSB	Hardware boundary	The XIAO boards use an external SAMD11 USB bridge. TinyUSB headers are compile-compatibility stubs and report unsupported at runtime.
Wi-Fi / Wi-Fi scanning	Hardware boundary	No Wi-Fi PHY or MAC is present; the 2.4 GHz radio cannot decode or associate with 802.11 networks.
Bluetooth Classic	Hardware boundary	The radio supports Bluetooth LE, not BR/EDR.
ANT and Nordic ESB	Missing	Raw proprietary-radio examples exist, but no supported ANT or Enhanced ShockBurst protocol stack is shipped.
Ethernet and CAN	Missing	No native stack or controller API is shipped. External devices can be driven by user libraries over SPI or UART.
Wireless OTA / secure DFU	Missing	No production BLE DFU, Zigbee OTA, Matter OTA Requestor/BDX, or generic wireless boot-update path is provided.

Bluetooth Low Energy

Implemented BLE rows refer to the documented single-active-link scope. They do not assert complete Bluetooth Core conformance, complete Bluefruit parity, or Bluetooth SIG qualification.

Capability	Status	Available now	Important boundary
Legacy advertising and scan response	Implemented	Connectable, scannable, non-connectable, background, and directed advertising with bounded high-duty timeout.	Continue broad phone and long-duration regression testing.
Active/passive scanning	Implemented	Filters, callbacks, scan responses, and central connection initiation.	Cross-platform stress coverage remains narrower than controller qualification.
Central and peripheral roles	Implemented	Both roles and dual-role examples are available.	The supported claim is one active connection; requested Bluefruit link counts do not create a production multi-link controller.
PHY, DLE, and ATT MTU	Implemented	LE 1M, 2M, Coded S2/S8, DLE through 251 bytes, and MTU through 247 bytes when requested.	Broader fallback and hostile-procedure timing tests remain.
Connection control	Partial	Parameter updates, reason reporting, reset recovery, and malformed CONNECT_IND validation.	Interleaved LL control-procedure collisions and multi-link stress are not complete.
Extended advertising/scanning	Partial	Non-connectable payload chains and local scanner reassembly through 995 bytes.	Extended-connectable, cross-vendor and extended scan-response coverage is incomplete.
Periodic advertising	Missing	The capability probe fails closed.	No periodic advertising scheduler or synchronization path.
GATT server and client	Implemented	16/128-bit UUIDs, discovery, reads/writes, CCCDs, notifications, and confirmed indications.	Formal ATT/GATT qualification is not complete.
Long values and descriptors	Implemented	Read Blob, Prepare/Execute Write, fixed/maximum lengths, and 0x2901, 0x2904, 0x2908 descriptors.	Broader phone/desktop edge-case interoperability remains.
Permissions and authorization	Implemented	Open, encrypted, authenticated/MITM and signed permissions plus deferred sketch-context authorization.	Host negative-test coverage remains incomplete.
Service Changed	Implemented	Per-bond database fingerprint, pending ranges, reconnect retry, and confirmation handling.	Not PTS-qualified.
GATT Robust Caching	Implemented	Database Hash, Client Supported Features, change-awareness and Database Out Of Sync behavior on the single ATT bearer.	EATT/multiple-bearer behavior is unavailable.
LE Secure Connections	Implemented	Just Works, fixed passkey, passkey input, Numeric Comparison, and mutual/one-way OOB.	A broader Android/iOS/desktop malformed, timeout and OOB matrix remains.
Bond database and key distribution	Implemented	Eight peers, LRU replacement, LTK/IRK/CSRK state, CCCDs, identity data, signing counters, enumeration and deletion.	Product provisioning and Bluetooth qualification remain separate.
Privacy and RPA	Partial	Stable identity, IRK exchange, rotating RPAs, hardware AAR, privacy-aware reconnects, and an application-managed resolving list.	No automatic controller-enforced resolving-list/allow-list policy.
Authenticated signed writes	Implemented	CSRK distribution, AES-CMAC, durable monotonic counters and replay rejection.	Broad phone/desktop signed-write interoperability is not established.
BLE UART / Nordic UART Service	Implemented	Peripheral/client APIs, buffered MTU-aware TX, notification/write and bridge examples.	Web/device bridge behavior remains in the regression matrix.
HID over GATT	Implemented	Keyboard, mouse, consumer control, gamepad, Report/Boot modes, Report Reference and keyboard LEDs.	Broad OS report parsing, gamepad and boot-mode testing remain.
Other bundled services	Implemented	Device Information, Battery, Current Time, ANCS parsing, beacons and custom services.	This is not every adopted Bluetooth profile or service.
Bluefruit52 compatibility	Partial	Common advertising, scanning, GATT, central/client, security, HID and service APIs compile and run.	Complete nRF52 Bluefruit API and behavioral parity is not claimed.
LE Credit-Based CoC and EATT	Missing	Fixed ATT/SMP/signaling L2CAP channels only.	No LE CoC or enhanced ATT bearers.
ISO, LE Audio, PAwR, AoA/AoD	Missing	No supported CIS/BIS, BIG, LE Audio, PAwR, direction-finding or mesh implementation.	These are outside the current practical BLE scope.
Nordic secure DFU	Missing	BLEDfu::begin() returns ERROR_NOT_SUPPORTED.	No non-working DFU service is advertised.
Phone/desktop interoperability	Partial	Multiple Android/iOS HID sessions and Linux diagnostic workflows have been exercised.	Repeatable Android, iOS, Windows, macOS and Linux coverage is not yet a release gate.
Bluetooth qualification	Missing	Repository tests and the two-board gate provide regression evidence.	No PTS/BQB, RF-PHY, controller, host, profile or end-product qualification claim.

See BLE implementation and qualification status and the two-board release gate.

IEEE 802.15.4

Capability	Status	Available now	Important boundary
2.4 GHz PHY	Implemented	250 kbit/s radio setup, 127-byte frames, CRC, channel/TX power, RSSI, CCA and energy detection.	Regulatory and RF-PHY qualification are product responsibilities.
ACK, filtering and receive queue	Implemented	TX ACK wait, automatic ACK, frame-pending callback, application/PAL filter callback, and buffered IRQ receive.	Hardware address matching is disabled; filtering policy is supplied by the caller. OpenThread installs one, while bundled Zigbee examples do not.
MAC frame/control primitives	Partial	Data, beacon, ACK, association, orphan, realignment and data-request helpers.	No complete reusable MAC service/PIB runtime.
CSMA-CA and retry engine	Missing	The radio API exposes one optional CCA check, but bundled Zigbee example transmissions currently disable it and perform one TX/ACK attempt.	No randomized BE backoff, retry queue or general duplicate table. OpenThread supplies its own software MAC behavior.
Raw-radio diagnostics	Implemented	Packet TX/RX, ACK, source-match and OpenThread PAL diagnostic examples.	These tests do not establish Zigbee or Thread conformance.

Zigbee

All Zigbee support remains experimental. An implemented primitive below does not make the overall stack Zigbee PRO compliant.

Capability	Status	Available now	Important boundary
Stack runtime architecture	Experimental	Shared codecs, security, persistence and commissioning helpers are used by bundled sketches.	Protocol behavior remains split across example-owned loops; there is no single event-driven coordinator/router/end-device runtime.
Direct NWK framing and security	Partial	Direct unicast codecs and AES-CCM* secured NWK frames.	Source-route and multicast frames are rejected by the generic codec.
NWK command set	Partial	Rejoin and End Device Timeout request/response commands.	Route Request/Reply/Record, Link/Network Status and Network Report/Update are absent.
Mesh routing and repair	Missing	Neighbor/routing table structures and management responses can expose sketch-owned entries.	No route discovery, aging, repair, many-to-one/source routing or production multi-hop forwarding.
APS group addressing and membership	Partial	APS group codecs and local group membership.	Fan-out is example-specific and not integrated with routing.
NWK broadcast/multicast forwarding	Missing	None.	No broadcast transaction table, rebroadcast jitter, multicast forwarding or general duplicate suppression.
Sleepy-child indirect delivery	Experimental	Frame-pending ACKs, polling, End Device Timeout negotiation and example-owned pending payloads.	No shared persistent child/indirect queue manager or long-duration parent test.
APS data/command/ACK codecs	Partial	Direct data/group/command frames, APS ACK, and Trust Center key commands.	Extended APS headers are not supported.
APS reliability	Experimental	A small retry/ACK mechanism exists in the HA coordinator example.	No reusable transaction manager, delivery backpressure or stack-wide retry policy.
APS fragmentation/reassembly	Missing	None.	Large application payload fragmentation is unavailable.
Binding, Groups and Scenes	Partial	Eight-entry binding tables, group codecs and local Groups/Scenes state.	Fan-out is example-specific and not integrated with production routing.
Scanning, association and rejoin	Partial	End-device steering, association, secure rejoin, leave handling and timeout negotiation helpers.	Full Zigbee Base Device Behavior and all-role commissioning policy are missing.
Cryptographic primitives	Implemented	AES-CCM*, NWK/APS security headers, ZigbeeAlliance09 key and install-code CRC/key derivation.	Primitive coverage does not establish a secure product lifecycle.
Keys and Trust Center lifecycle	Partial	Active/alternate network-key transport and switch paths.	No production device/link-key table, full authorization policy or distributed-security runtime.
Replay counters and persistence	Partial	Network identity, keys, counters, reporting and bindings can persist.	Incoming counters are not per-neighbor and storage is not proven brownout-atomic.
ZDO	Partial	Address/descriptor discovery, match, bind/unbind, leave and management table responses.	No general transaction timeout/retry/concurrency or Network Update manager.
ZCL foundation	Partial	Read/write/discover/reporting/default-response helpers for a limited type set.	Structured and manufacturer-specific data plus general endpoint stores are incomplete.
ZCL clusters	Partial	Selected Basic, Power, Identify, Groups, Scenes, On/Off, Level, Color, Temperature and Humidity server paths.	Complete client/server commands and broad cluster coverage are not present.
End-device and sleepy examples	Experimental	Joinable lights, sensors and buttons, including 15/60-second sleepy examples.	Behavior is sketch-specific and unqualified.
Router role	Experimental	Rx-on router-capable examples can join.	Without route discovery/relay/repair this is not a production Zigbee PRO router.
Coordinator / Trust Center	Experimental	The HA coordinator can form a network and admit/interview bundled examples.	Fixed small RAM tables and sketch-owned policy are not restart-safe production Trust Center behavior.
Zigbee OTA Upgrade	Missing	Only the cluster identifier is present.	No client/server, image verification, resume or boot handoff.
Green Power Proxy Basic	Missing	None.	Required for a Zigbee 3.0 routing-capable certification claim.
Touchlink, Zigbee Direct, WWAH, NCP/RCP	Missing	None.	Outside the current implementation.
Zigbee2MQTT / Home Assistant	Experimental	Documented join/interview/state tests and an external converter for bundled models.	The converter is not upstream and coverage is not a broad ecosystem matrix.
Example and host regression coverage	Partial	Thirty bundled Zigbee sketches and local serial/MQTT validation scripts exist.	Main CI compiles five Zigbee sketches, and no native Zigbee codec/security test suite exists under tests/.
Multi-hop, soak and certification	Missing	Two-board and coordinator integration scripts exist.	No three-node route/repair gate, mixed-vendor soak, ZUTH result or compliant-platform certification.

See the Zigbee full-support handoff and Zigbee2MQTT integration guide.

Thread

Thread uses a real imported OpenThread FTD core. The experimental status refers to this nRF54 platform port and its validation, not to the quality or certification status of upstream OpenThread.

Capability	Status	Available now	Important boundary
Imported OpenThread FTD core	Implemented	Pinned upstream source is compiled when the experimental Thread stage is selected.	This nRF54 platform port is not a certified OpenThread platform.
nRF54 radio/platform layer	Experimental	Radio, alarm, entropy, reset and settings PAL plus cooperative processing.	Cooperative polling and incomplete power/interoperability evidence remain.
Formation and FTD roles	Experimental	Dataset setup and Leader, Router and Child paths; mixed L15/LM20A Leader/Child hardware validation.	No production multi-hop/router topology matrix.
IPv6, 6LoWPAN and mesh	Experimental	Upstream OpenThread networking exercised on a local two-board network.	No external OTBR, cross-vendor, interference or long-duration route test.
UDP, multicast and fragmentation	Implemented	Four sockets, explicit close, both unicast directions, multicast and payloads through 512 bytes.	This is local mixed-board transport evidence, not general interoperability.
Application CoAP / Secure CoAP APIs	Missing	MeshCoP internally uses CoAP/DTLS components.	OPENTHREAD_CONFIG_COAP_API_ENABLE and OPENTHREAD_CONFIG_COAP_SECURE_API_ENABLE remain disabled; no supported application API or interoperability gate is shipped.
MeshCoP Commissioner and Joiner	Experimental	Fresh PSKd join, reset-only dataset restore and exact wrong-PSKd rejection pass on two boards.	External Commissioner/Border Agent interoperability and broader negatives are missing.
Operational Dataset persistence	Partial	Normal restart preserves settings and reported storage failures retain the prior mapping.	Shared Preferences storage is not journaled/dual-bank or proven under controlled brownout.
SRP client; DNS client with Matter stage	Partial	SRP client and auto-start are built into Thread stage; the DNS client is enabled only when Matter stage also enables DNS-SD.	No external OTBR/SRP registration, removal, reboot or DNS-SD visibility gate. mDNS/server paths are disabled.
Thread security and entropy	Experimental	Upstream mbedTLS plus fail-closed CRACEN entropy; correct/wrong PSKd paths pass locally.	No Thread security conformance or fault/attack campaign.
Sleepy End Device	Experimental	Sleepy-child attach and poll APIs/examples; software CSL parameters are recorded.	The polling PAL has no hardware-timed CSL wakeups; sleep current, missed-poll recovery, parent interoperability and long soaks remain.
Border Router / Border Agent / Backbone Router	Missing	None in the shipped profile.	Use an external OTBR; no onboard NAT64, infrastructure routing or Border Agent.
Advanced optional services	Missing	TCP, channel manager/monitor, jam detection, history, network time and the full link-metrics manager are disabled; upstream CLI, POSIX, NCP/RCP and spinel transport were omitted from the import.	Upstream header presence does not make these available.
External interoperability	Missing	Repo-owned two-board gates only.	No completed OTBR, cross-vendor, three-node, RF-loss or long-duration matrix.
Thread certification	Missing	None.	No Thread conformance harness or product certification has passed.

See Thread and Matter hardening status.

Matter

The Matter entries rate standards-compatible behavior. Private PASE-like, CASE-like, certificate and command demos are useful tests but are not marked as standard Matter features.

Capability	Status	Available now	Important boundary
Upstream connectedhomeip foundation intake	Partial	Selected support, System Layer, PacketBuffer, error/key/time and Thread-dataset units are imported.	There is no complete upstream Matter server/runtime.
System clock, timers and work queue	Implemented	Monotonic clock and mutation-safe cooperative timer/work dispatch with host regressions.	A platform foundation is not a Matter device stack.
Crypto foundations	Implemented	SHA-256, HKDF, PBKDF2, AES-CCM, P-256 ECDH/ECDSA and DRBG entry points with fail-closed entropy.	P-256 is software and these primitives are not connected to an upstream Secure Channel.
CHIP PacketBuffer, IPv6 and UDP Inet	Experimental	Four queued endpoints, 1280-byte IPv6 datagrams, a private multicast transport probe and bidirectional payloads through 1200 bytes on two boards.	Transport validation only.
Setup payload helpers	Experimental	Manual/QR payload and setup identity helpers.	They do not prove successful standard commissioning.
DNS-SD / SRP discovery	Partial	Demo commissionable records can be built, queued and removed through OpenThread SRP.	No external OTBR/controller has verified publication or discovery.
Standard PASE / SPAKE2+	Missing	A fail-closed private PASE-like experiment exists.	Its framing/transcript is not Matter wire-compatible and cannot commission with a standard controller.
BLE commissioning rendezvous	Missing	None; the current profile is on-network only.	No standard Matter BLE commissioning service or transport.
Standard CASE sessions	Missing	A private Sigma-style tamper/replay experiment exists.	Private certificates, encodings and key schedule are not wire-compatible CASE.
Exchange Manager and reliable messaging	Missing	None from the upstream runtime.	Local message headers/counters do not replace Matter exchanges and retransmission.
Interaction Model and generated data model	Missing	Project-specific On/Off, Level, Identify and Scenes objects exist.	No upstream IM engine, subscription/reporting engine or generated endpoint model.
Group communication and key management	Missing	None from the upstream runtime.	No Group Data Provider, group sessions/key sets, secured multicast commands or standard Groups-cluster integration.
Access control	Experimental	Local ACL checks fail closed unless complete subject/fabric/node context is supplied.	Not connected to standard fabrics, CASE subjects or Access Control cluster persistence.
Fabric and operational credentials	Missing	A small in-memory demo fabric table exists.	No standard NOC/RCAC/ICAC provisioning, persisted multi-fabric lifecycle, keystore or fail-safe transaction.
Device Attestation	Missing	Test-only PAA/PAI/DAC-like objects and regressions.	Keys are regenerated and encodings are private; no standard DAC chain or Certification Declaration.
Persistence	Partial	Demo setup identity, Thread dataset, factory data and light state use Preferences.	Standard fabrics, ACLs, credentials, sessions and counters are not durably managed or brownout-proven.
OTA Requestor and BDX	Missing	Excluded from the staged upstream intake.	No Matter OTA runtime.
ICD / low-power Matter device	Missing	Thread has a separate experimental sleepy-child path.	No upstream ICD server, check-in protocol or Matter-aware sleepy lifecycle.
Ecosystem interoperability	Missing	Private two-board demos only.	No successful commissioning/control with chip-tool, Home Assistant, Google Home, Apple Home or SmartThings.
Matter certification	Missing	None.	No CSA test harness, production credentials or ecosystem certification.

See Thread and Matter hardening status.

Bluetooth LE Channel Sounding

Capability	Status	Available now	Important boundary
Controller-backed LE CS Test	Experimental	Nordic SDC/MPSL runs the controller procedure on two supported boards.	This is a test procedure, not a complete connected BLE Channel Sounding product path.
Initiator and reflector examples	Implemented	Two public examples with a CRC-protected session/result exchange.	Both sides must use this core’s private transport.
Mode and antenna support	Experimental	Single-antenna Mode 2/Submode 1 with AA-only RTT.	No multi-antenna, AoA/AoD or full mode matrix.
Connected-ACL Channel Sounding	Missing	None.	No standards-complete LL control workflow attached to a normal BLE ACL.
Calibrated distance estimation	Missing	Raw/test results and diagnostics only.	No production calibration, accuracy or environmental model.
Cross-vendor interoperability and qualification	Missing	Local two-board hardware validation only.	No Bluetooth qualification or cross-vendor controller evidence.

See Channel Sounding current status.

Arduino APIs, Buses, Storage, and Board Hardware

Capability	Status	Available now	Important boundary
Startup, millis, micros, delay	Implemented	Arduino sketch lifecycle and a shared monotonic timebase across supported MCU variants.	Continue long-duration drift and mixed-radio regression testing.
GPIO	Implemented	pinMode, digitalRead, digitalWrite and lower-level port access.	Board pin routing still applies.
External interrupts	Partial	GPIOTE-backed rising/falling/change on interrupt-capable ports.	Port P2 has no interrupt or wake capability in hardware.
ADC / SAADC	Implemented	analogRead, resolution control, internal-supply helpers, gain and oversampling APIs.	Board-specific calibration affects absolute accuracy.
PWM	Implemented	analogWrite, global/per-pin frequency paths and hardware/timer/software allocation.	Frequencies and channels share finite PWM/timer resources.
UART/UARTE	Implemented	Serial, Serial1, compatible extra routes and lower-level UARTE APIs.	The XIAO USB serial path is an external bridge, not native USB CDC.
I2C controller (Wire)	Implemented	Wire, Wire1, repeated starts and lower-level TWIM access.	Pin mux and serial-fabric ownership are board-specific. Empty writes require STOP; see address-probe behavior.
I2C target (TWIS)	Partial	Target callbacks and TWIS21/TWIS30 examples.	Multi-instance and stress validation are narrower than controller mode.
SPI controller	Implemented	Arduino SPI, lower-level SPIM and selected multi-instance examples.	Maximum usable speed depends on instance, pins and board routing.
SPI target (SPIS)	Partial	SPIS wrapper and target echo example.	Broad multi-instance/high-speed validation is incomplete.
SPI_HS / external QSPI pads	Implemented	LM20A onboard flash and deliberate high-speed/QSPI-pad access.	SPI_HS is not the normal XIAO header SPI bus.
I2S (nRF54L15 only)	Implemented	TX, RX and duplex wrappers with interrupt examples.	nRF54LM20A has TDM rather than I2S; this core does not expose a TDM API.
TDM (nRF54LM20A)	Missing	None.	The LM20A TDM peripheral is not wrapped by this core.
PDM	Implemented	PDM20/PDM21 capture and board microphone examples.	Pin/base selection and microphone wiring differ by board.
QDEC	Implemented	QDEC20/QDEC21 wrapper and encoder example.	External encoder hardware is required.
NFC-A / NFCT	Partial	Low-level NFCT and tag setup path.	Most supported XIAO boards do not provide a ready-to-use NFC antenna.
Comparator / LPCOMP	Implemented	Threshold, window and wake examples.	Analog routing and threshold accuracy are board-dependent.
Watchdog	Implemented	WDT wrapper and examples.	Multi-instance product policy remains application-owned.
GRTC / low-frequency PWM	Partial	Timekeeping, compare, wake and fixed-pin GRTC PWM examples.	Continuous waveform validation is limited by board pin conflicts.
DPPI / EGU	Implemented	Hardware event/task routing wrappers and examples.	Domain and channel ownership must be coordinated by the sketch.
EEPROM / Preferences	Implemented	RRAM-backed Arduino-style persistence used by bonds and staged protocol state.	Shared storage is capacity-limited and not a journaled brownout-atomic database.
LM20A external flash	Implemented	PY25Q64 JEDEC/read/write/erase and deep-power-down paths plus SPIFlash examples.	LM20A-specific; other boards may use different or no external flash.
VPR RISC-V control	Partial	Boot/reset, shared memory, RPC transport, ticker and checksum/offload probes.	No stable general-purpose coprocessor framework or resource scheduler.
VPR SoftPeripheral / sQSPI	Experimental	Host wrappers, RPC definitions, firmware scaffolding and a flash probe exist.	The complete firmware pair and low-power restoration are not established across supported boards.
nPM1300 PMIC	Implemented	Charger, VBUS limit, rails, telemetry, hibernate and battery-current examples.	Not present on the L15 XIAO.
System ON/OFF power APIs	Implemented	Low-power idle, timed System OFF, reset-cause APIs, RF-switch and board-specific shutdown helpers.	Measured current depends on debugger, LEDs, sensors, USB and board configuration.
Sense IMU and microphone	Implemented	LSM6DS3TR-C IMU and board-specific PDM microphone examples for supported Sense variants.	Selecting a non-Sense board does not add the sensors.
TinyUSB / native USB device	Missing	Compile-compatibility headers return unsupported.	Upload and serial use the board’s external CMSIS-DAP/SAMD11 bridge.
I3C	Hardware boundary	None.	nRF54L exposes I2C controller/target blocks rather than I3C.

See the board reference for pin, peripheral-instance, sensor and routing details.

Crypto, Keys, and Tamper

Capability	Status	Available now	Important boundary
CRACEN entropy/RNG	Implemented	Hardware entropy source used fail-closed by BLE and staged Thread/Matter paths.	Product health monitoring and formal validation remain product concerns.
Hardware AAR, ECB and CCM	Implemented	Address resolution and BLE AES operations.	This does not automatically accelerate all Thread/Matter crypto.
Software hashes, HMAC, HKDF, PBKDF2 and AES-CCM	Implemented	mbedTLS-backed CHIP primitives plus the local streaming SHA-256/HMAC/PBKDF2 helper, with host vectors.	Full protocol conformance depends on the surrounding standard stack.
Software secp256r1	Implemented	P-256 key generation/ECDH for BLE Secure Connections and ECDH/ECDSA for private Matter experiments.	Software arithmetic is comparatively slow; the Matter path is not connected to a standard upstream Secure Channel.
CRACEN PKE acceleration	Missing	Nordic publishes Nordic-IC-only PKE microcode and an accompanying NCS driver for CRACEN Base devices such as nRF54L15.	This core does not ship/load that path; nRF54LM20A uses CRACEN Lite and is not a target for this PKE microcode.
KMU	Partial	Low-level slot metadata/task APIs and constrained IKG paths.	No complete product provisioning, rotation and protocol-consumer lifecycle.
Tamper/glitch detection	Partial	TAMPC/control wrappers and diagnostic examples.	External tamper, reset behavior and secure product policy need hardware characterization.
Production credentials	Missing	Development/test credentials exist in experimental paths.	No manufacturing provisioning system for Matter DACs, Zigbee Trust Center identity, or comparable product secrets.

---

Bluetooth LE

Bluetooth LE is the core’s primary wireless surface. It uses a clean, register-level host/controller implementation for normal BLE operation and ships a Bluefruit52Lib compatibility layer so familiar Adafruit-style sketches can be moved to nRF54L with limited changes.

Implemented Surface

Layer	Available functionality
GAP	Advertising, active/passive scanning, central and peripheral roles, dual-role examples, connection parameter updates, RSSI, 1M/2M/Coded PHY, and reconnect behavior
ATT/GATT	Server and client discovery, 16-bit and 128-bit UUIDs, services, characteristics, descriptors, CCCDs, long reads/writes, fixed/maximum value lengths, notifications, indications, MTU 247, and DLE 251 paths
Compatibility services	BLE UART/NUS, Device Information, Battery, HID keyboard/mouse/gamepad, Current Time, ANCS notification and fragmented attribute handling, beacons, and custom services
Security	LE Secure Connections, Just Works, passkey/PIN flows, asynchronous Numeric Comparison, mutual and one-way OOB, bonding, negotiated 7-16-byte key sizes, CSRK signed writes, and authenticated access permissions
Privacy	Stable identity, local IRK derivation, rotating RPAs, identity-key distribution, eight-peer bond storage, direct/identity/RPA selection, and privacy-aware directed reconnect
Reliability	Encrypted retransmission/counter handling, signed-write anti-replay counters, SMP timeout and repeated-attempt controls, fail-closed CRACEN entropy, and release-gate positive/negative pairing tests

The two-board release gate checks advertising, discovery, CCCDs, PHY changes, MTU/DLE, long notifications, pairing, bond reload, encrypted reconnect, Numeric Comparison acceptance and rejection, all three OOB directions, RPA rotation, identity-key distribution, AAR-based bond resolution, and signed writes with persisted monotonic counters plus replay rejection. See Two-Board Release Gate for the exact scope and test procedure.

Choosing An API

• Use #include <bluefruit.h> for the largest example set and compatibility with common Bluefruit sketches.
• Start with Bluefruit52Lib > Peripheral > bleuart for a phone or computer peripheral, or Bluefruit52Lib > Central > central_bleuart for a central.
• Use BLEService and BLECharacteristic for custom GATT services. Configure properties, permissions, fixed or variable length, and callbacks before calling begin().
• Use Bluefruit.Security and characteristic permissions when a value must be encrypted or authenticated. Numeric Comparison requires an explicit asynchronous accept/reject response; the bundled example shows the complete flow.
• Use Bluefruit.Security.enumerateBonds(), getBondInfo(), deleteBond(), and clearBonds() to manage up to eight built-in peer records. The legacy custom persistence callback interface remains intentionally capacity-one.
• Use the lower-level examples under Nrf54L15-Clean-Implementation for radio, privacy, crypto, and hardware diagnostics where compatibility wrappers would hide the behavior being tested. A normal peripheral sketch follows this order:

1. Create service and characteristic objects globally.
2. Call Bluefruit.begin(), set the device name and TX power, and register connection callbacks.
3. Configure security before starting protected services.
4. Configure and start each GATT service.
5. Add flags, advertised services, and the device name to the advertising and scan-response payloads.
6. Enable restart-on-disconnect, select advertising intervals, and call Bluefruit.Advertising.start().

BLE Scope Boundary

The core’s BLE claim is intentionally narrower than “all Bluetooth LE.” It does not claim Bluetooth SIG qualification or complete Core conformance. Locally generated legacy bond-key distribution and the built-in multi-bond privacy store are implemented; automatic controller-enforced allow-list policy, broad cross-vendor negative testing, and PTS/BQB remain outside the validated scope. The built-in store retains up to eight peers with isolated signing counters, CCCDs, privacy identities, and Service Changed state. Nordic secure DFU is not implemented, and BLEDfu::begin() returns ERROR_NOT_SUPPORTED. Legacy directed advertising is supported with explicit target selection and compliant high-duty scheduling. Service Changed tracking persists a structural database fingerprint and pending handle range per bond, retries on encrypted reconnects, and clears the range only after ATT confirmation. Channel Sounding is separate from the normal connected BLE stack and remains experimental, as documented below.

---

Power Consumption

The core has board-specific low-power behavior rather than treating sleep as a CPU-only operation. On XIAO nRF54L15 it controls the external RF switch around radio activity. On XIAO nRF54LM20A it coordinates the nPM1300, oscillator state, RAM retention, and the onboard QSPI flash’s deep-power-down mode.

For the 1.0.18 L15/LM20A startup-charge and idle-current comparison, see the issue #114 investigation and the ble_power_breakdown PPK2 diagnostic. Version 1.0.19 removes eager BLE pairing-key generation and restores PMIC measurement settings after telemetry reads. Updated current measurements are pending; the historical captures below remain attributed to their original versions.

Community PPK2 Measurements

These are measured board-level snapshots, not datasheet limits or guaranteed production figures. They depend on the core version, sketch, radio settings, power path, board revision, instrument wiring, temperature, attached probes, and peripherals. USB/debug connections can dominate microamp measurements.

Delay and System OFF, side by side

*Community PPK2 comparison posted 14 June 2026: the LM20A trace (left) labels returning delay() at abou

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