Wi-SUN SDK Version 2.12.0 - Release Notes (Jun 23, 2026)#

Wireless Smart Ubiquitous Network (Wi-SUN) is the leading IPv6 sub-GHz mesh technology for smart city and smart utility applications. Wi-SUN brings Smart Ubiquitous Networks to service providers, utilities, municipalities/local government, and other enterprises by enabling interoperable, multi-service, and secure wireless mesh networks. Wi-SUN can be used for large-scale outdoor IoT wireless communication networks in a wide range of applications covering both line-powered and battery-powered nodes.

Silicon Labs' Wi-SUN hardware is certified by the Wi-SUN Alliance, a global industry association devoted to seamless LPWAN connectivity. Wi-SUN builds upon open standard internet protocols (IP) and APIs, enabling developers to extend existing infrastructure platforms to add new capabilities. Built to scale with long-range capabilities, high-data throughput, and IPv6 support, Wi-SUN simplifies wireless infrastructure for industrial applications and the evolution of smart cities.

Release Summary#

Key Features | API Changes | Bug Fixes | Chip Enablement

Key Features#

• Added automatic connection parameter selection. The stack can now automatically optimize connection parameters based on the PAN size, and adapt the parameters as the size changes. This replaces the fixed legacy connection parameter configurations and predefined parameter sets.

• Introduced an optional component to allocate a separate heap for critical Wi-SUN functions. The component reserves a separate configurable heap for critical Wi-SUN stack and cryptographic allocations, allowing the Wi-SUN connection to be maintained even when the system heap is exhausted.

• Added support for Direct Connect client. The application can now act as a Direct Connect client with scanning capabilities, complementing the existing server role.

  • The client opens a secure, single-hop IPv6 wireless link to a Direct Connect server.

  • The client is available as a standalone stack variant or together with FFN; it is not supported with LFN or Border Router (BR). When used with FFN, the DC link can run alongside an active or in-progress Wi-SUN mesh connection.

• Added support for First Breath mode. First Breath enables an FFN to send expedited upstream application data after a network outage before the node reaches full operational connectivity.

• Added support for Last Gasp mode. FFNs can enter a low-energy Last Gasp mode to deliver a final burst of traffic before power loss.

• Expanded RF test component with TX and RX modes. RF test component now supports dedicated transmission and reception test modes for high-volume production testing.

API Changes#

• Added new APIs for fine-tuning the automatic parameter selection

• Added new APIs for Direct Connect client

• Added an API to insert vendor-specific data into DHCPv6 Solicit messages

• Added an API to control First Breath mode

• Added an API to control Last Gasp mode

• Deprecated a few legacy configuration parameters

• Deprecated a few API flags related to certificate configuration

Bug Fixes#

• Enhanced processing of malformed channel-mask IEs for better interoperability with third-party devices

• Fixed various LFN multicast issues

• Fixed several LFN stability and scheduling issues

• Fixed routing, forwarding, and DAO-related edge cases

• Fixed socket error propagation after connection teardown

Chip Enablement#

None.

Key Features#

New Features | Enhancements | Removed Features | Deprecated Features

New Features#

• Automatic connection parameter selection: By default, the stack will optimize connection parameters based on the PAN size, and adapt the parameters as the size changes. Parameters that are not automatically adapted can be fine-tuned using sl_wisun_set_option(), otherwise they will utilize the fixed default values. The application can override the adapted parameters by specifying explicit values using sl_wisun_set_ffn_advanced_parameters(), sl_wisun_set_lfn_advanced_parameters(), or sl_wisun_br_set_advanced_parameters().

  It's possible to revert back to the legacy fixed configuration by using sl_wisun_set_connection_parameters(), sl_wisun_set_lfn_parameters(), or sl_wisun_br_set_connection_parameters(). While the legacy configuration parameters are not deprecated, developers are encouraged to adapt the new configuration APIs.

• Separate Wi-SUN heap: The application can include an optional wisun_alloc component during project generation. This reserves a separate, application-configurable heap used for critical features needed to maintain the Wi-SUN connection even when the system heap is exhausted. Care should be taken to size the heap correctly since any cryptographic operations performed by the application will also utilize this heap.

• Direct Connect client: This client allows a device to establish a secure, single-hop wireless link to a Direct Connect server, enabling fast, direct IPv6 communication outside of the Wi-SUN network. The client is supported only as a standalone library or together with FFN; it is not available in LFN or BR. When used with FFN, the DC client and Wi-SUN mesh connection operate independently without disturbing each other. As part of the enhanced Direct Connect support, the DC server has been extended to advertise a DC server identity. This allows the client to search for a unique server identity or identify a particular server when multiple servers are available.

• First Breath mode: First Breath is a feature that allows a Wi-SUN FFN to rapidly deliver critical application data upstream following a network outage or a device reboot, before the node completes full joining process. This enables applications to expedite high-priority messages (such as alerts or maintenance signals) without waiting for the full operational state. The feature is controlled using sl_wisun_set_first_breath() and the application receives SL_WISUN_MSG_FB_READY_IND event when the node is ready for expedited traffic.

• Last Gasp mode: When an FFN detects imminent power failure, Last Gasp mode enables the node to temporarily maintain network connectivity and send a final burst of high-priority messages, such as alerts or telemetry, before shutting down. This capability boosts the reliability of critical event reporting in power-constrained scenarios. The feature is managed with the sl_wisun_set_last_gasp() API.

• Vendor-specific data in DHCPv6 Solicit messages: sl_wisun_set_dhcpv6_vendor_data() allows the application to insert vendor-specific data into the DHCPv6 Solicit messages that are sent when joining a Wi-SUN network and when DHCP lease is renewed.

• Event Task: Wi-SUN event processing has been moved to a separate wisun_event_task component that's included by default. The application can override this by including wisun_disable_event_task component which allows the application to consume events directly from the underlying Event System instead of sl_wisun_on_event() callback.

• Channel Mask for Explicit Channel Plans: Added a channel_mask field to sl_wisun_phy_config_explicit_t to restrict the set of channels on which the device is permitted to transmit. The mask applies to asynchronous, unicast, and broadcast frames, and is advertised in both US-IE and BS-IE.

• Expanded RF Test Component: Extended the wisun_rf_test component with dedicated TX and RX test modes to support high-volume production testing. The PHY configuration can be selected from the command line.

Enhancements#

• LFN improvements

  • LFN adapts listening strategy based on measured parent drift

  • Improved LFN recovery after parent reboot

  • Increased LFN multicast group enrollment support up to 8 groups

• Improved asynchronous frame TX fairness between nodes

• Improved key rotation reliability by retrying key fetches through the rotation window

• Persisted RPL DODAG ID and DAO sequence in NVM to reduce route instability

• Optimized the size of stack release libraries by removing unnecessary strings

• Improved socket POSIX compatibility

  • Reorganized socket header placement to better align with POSIX

  • Updated IPV6_TCLASS socket option to make it RFC3542 compliant

• Optimized authenticator heap usage to support larger networks on memory-constrained SoC Border Routers

Removed Features#

None.

Deprecated Features#

None.

API Changes#

New APIs | Modified APIs | Removed APIs | Deprecated APIs

New APIs#

Modified APIs#

Removed APIs#

None.

Deprecated APIs#

Bug Fixes#

Chip Enablement#

None.

Application Example Changes#

New Examples | Modified Examples | Removed Examples | Deprecated Examples

New Examples#

Modified Examples#

Removed Examples#

None.

Deprecated Examples#

None.

Known Issues and Limitations#

None.

Impact of Release Changes#

Impact Statements | Migration Guide

Impact Statements#

None.

Migration Guide#

sl_wisun_regdb.c is generated only once at project creation and is not automatically regenerated when upgrading the SDK. Because the file is user-modifiable, any fixes or updates introduced in newer SDK versions within sl_wisun_regdb.c are not applied automatically after migration. When upgrading, manually compare your project's sl_wisun_regdb.c with the latest version shipped in the SDK and merge the required changes to ensure all fixes are included.

Using This Release#

What's in the Release?#

This release contains the following:

• Wi-SUN stack library

• Wi-SUN sample applications

• Wi-SUN border router and RCP pre-compiled demos

• Documentation

If you are a first-time user, see the Wi-SUN Getting Started Guide.

Compatible Software#

Installation and Use#

The Wi-SUN SDK is distributed as part of the Simplicity SDK, Silicon Labs' unified software development kit suite. To get started quickly, install Simplicity Studio 6, which provides a complete development environment, including project and resource management, software configuration tools, a full IDE with GNU toolchain, and analysis utilities. Step-by-step installation instructions are available in the Simplicity Studio 6 User’s Guide.

Documentation for each SDK version is included with the SDK installation.

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SDK Release and Maintenance Policy#

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