SEGGER RTT Integration

Overview

Use this skill to integrate SEGGER RTT as a low-intrusion debug channel. Prove the RTT control block, buffer configuration, J-Link connection, and blocking policy before relying on RTT logs in timing-sensitive firmware.

When To Use

Use this skill when:

• The user wants SEGGER RTT logs or terminal input on an MCU.
• RTT Viewer/J-Link cannot find the control block, logs are missing, output blocks, or input commands fail.
• The task involves RTT buffers, up/down channels, blocking modes, J-Link, SystemView, or debug builds.

Do not use this skill when the debug probe cannot connect. Use architecture or flashing debug skills first.

First Questions

Ask for:

• MCU/core, debug probe, J-Link software version, and IDE/toolchain.
• RTT source files/config and whether SEGGER_RTT_Init() is called.
• Output mode: blocking, no-block-skip, or no-block-trim.
• Buffer sizes and channels used.
• Whether caches, MPU, low power, or secure/non-secure memory are involved.

Integration Checklist

1. Include RTT sources once. Avoid duplicate control blocks from multiple copies of RTT source.

2. Place control block in accessible RAM. J-Link must be able to locate and read the RTT control block.

3. Configure buffer policy. Blocking output can disturb real-time behavior; choose mode intentionally.

4. Verify host tooling. RTT Viewer, J-Link console, IDE plugin, or SystemView must attach to the correct target.

5. Handle cache and low power. Cacheable memory and deep sleep can hide or disrupt RTT buffers.

Common Failures

• Control block optimized out or duplicated.
• RTT logs block because host is disconnected and blocking mode is used.
• Buffers too small for burst logs.
• J-Link scans wrong RAM region.
• Cache prevents host from seeing updated data on some cores.

Verification

Before claiming RTT works:

• State probe, RTT source/config, buffer sizes, and blocking mode.
• Confirm host tool sees the control block.
• Confirm one output channel and one input channel if input is needed.
• Confirm behavior with host disconnected if product timing matters.

Example

User:

SEGGER RTT Viewer 连上了但没有日志。

Agent:

1. Asks for RTT config, init path, J-Link target, and map/control block placement.
2. Checks duplicate RTT sources and buffer mode.
3. Verifies a minimal early boot RTT print.