Understanding LTS and STS Releases for SimpleLink SDK

Texas Instruments now offers two types of SIMPLELINK SDK release streams: Long-term support (LTS) and Short-term support (STS). This document explains the differences, version numbering, compatibility guarantees, and support policies for each.

Two Support Tracks: LTS and STS

The SIMPLELINK SDK offers two parallel support tracks to serve different project needs:

Both tracks run simultaneously, allowing you to choose the approach that best fits your project requirements.

What's the Difference?

LTS releases provide stability and predictability:

STS releases provide innovation and latest features:

IMPORTANT: The quality of STS releases is the same as LTS releases. Both go through the same validation and testing processes.

Understanding Version Numbers

SIMPLELINK SDK uses a four-part version number, MM.mm.pp.bb, where:

For example: 9.10.01.17

Segment Meaning
Major.Minor The release stream (e.g., 9.10)
Patch Bug fix releases within that stream
Build Specific build number

LTS Version Numbers

For LTS releases, Major.Minor stays the same throughout the 3-year support period. Only Patch and Build increment.

Example of an LTS stream:

9.10.00.52  (Initial LTS Release)
    ↓
9.10.01.17  (Maintenance Release 1)  ← Fully Compatible
    ↓
9.10.02.03  (Maintenance Release 2)  ← Fully Compatible

STS Version Numbers

For STS releases, any part of the version number may change. There is no compatibility guarantee between STS versions.

Example of an STS progression:

9.10.00.52  (STS Q1) ──┐
                        │ May have breaking changes
9.11.00.12  (STS Q2) ──┤ (new features, dependencies)
                        │
9.12.00.45  (STS Q3) ──┤
                        │
10.00.00.01 (LTS)   ───┘

Active vs Inactive Release Streams

A release stream is a group of related releases that differ only in the Patch and Build numbers (same Major.Minor).

Each LTS stream has a status:

Active Streams:

Inactive Streams:

The last two LTS streams are active. All previous LTS streams are inactive.

STS releases are always considered "active" until the next STS or LTS release, at which point they become inactive.

Support Model

LTS Support Policy

LTS releases are:

Priority When Fixed
Critical (S1/P1) In next maintenance release (typically 2 per year)
Security (PSIRT) In next maintenance release (typically 2 per year)
Other Priority Not fixed in LTS (may be fixed in STS)

Note: Critical bugs discovered in STS releases are backported to active LTS releases if applicable.

STS Support Policy

STS releases are:

Compatibility Between SDK Versions

General Compatibility Principles

Code developed with older SDK versions is usually compatible with newer SDK versions, but there are exceptions. When building a project, all object files and libraries should be compiled with the same SDK version.

The most important rule: When building a project, all object files and libraries should be compiled with the same SDK version.

LTS Compatibility Guarantee

Within an LTS stream (same Major.Minor), full API/ABI compatibility is guaranteed:

STS Compatibility: No Guarantees

STS versions do not guarantee compatibility between releases, even within the same quarter:

SIMPLELINK SDK LTS vs STS: Comparison Summary

Feature LTS STS
Release Frequency Every 2 years Up to 3 releases a year
Support Duration 3 years Until next release
New Features No new features New features and enhancements
Bug Fix Approach Critical bugs (S1/P1 + PSIRT) backported to active LTS Bugs fixed forward in next release only
Maintenance Updates Up to ~2 maintenance releases/year No maintenance releases
Version Compatibility Maintains Major.Minor compatibility (patch-level updates only) Version may change with dependencies
Dependency Updates No new dependencies introduced New dependencies may be introduced
Ideal Use Case Long-term projects requiring stability Projects needing latest features and rapid innovation
Backport Policy P1/PSIRT bugs backported from STS if present No backporting from future releases
Toolchain Requirements Frozen at LTS release May require latest versions

Frequently Asked Questions

When Does LTS Begin? LTS releases begin no later than 1 year after device/product RTM (Ready to Market).

Can I mix LTS and STS in the same project? No, not recommended. Choose one track and stick with it for a given project. Mixing tracks creates compatibility risks and complicates support.

If I start with STS, can I switch to LTS later? Yes, but plan for it. Switching from STS to LTS may require code changes due to API differences. Treat it as a migration, not a drop-in upgrade.

How do I know which streams are active? Check the SimpleLink SDK release notes or contact TI support. Generally, the last two LTS streams are active.

Do I need to update my toolchain when I update the SDK?

What if I find a critical security issue on an inactive LTS stream? Contact TI support immediately. Security issues (PSIRT) may be addressed even on inactive streams depending on severity and customer impact.

Can I get commercial support for STS releases? Yes. Both LTS and STS releases are fully supported by TI. The difference is the duration of support - LTS provides 3 years, STS provides approximately 4 months.

What happens when my LTS reaches end-of-life (3 years)? Your LTS stream becomes inactive. No further maintenance releases or bug fixes. Plan to migrate to the next LTS stream before end-of-life.