RTT Ramcode Sample for Cortex-M0+ (Keil MDK)

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This article describes how to get started with RTT within RAM on a Cortex-M0+ device. This article assumes that there is already a basic knowledge about RTT in general (what is RTT, etc.). If this is not the case, we recommend to read RTT chapter in the J-Link User Manual (UM08001).

Minimum requirements

In order to use ETB trace on the ATMEL ATSAMD21 devices, the following minimum requirements have to be met:

  • J-Link software version V6.44g or later
  • µVision V5.24.2.0 or later (if the sample project from below shall be used)
  • J-Link Plus HW version V10.1 or later

Sample project

RTT Ramcode

The following sample project is designed to be used with J-Link and Keil MDK to demonstrate RTT. The project has been tested with the minimum requirements mentioned above and a SAMD21 XPlained Pro evalboard. The sample project comes with a pre-configured project for Keil MDK that runs out-of-the box.



  • After downloading and unzipping the project, open it with Keil µVision V5.24.2.0 or later.
  • Remark: When using another Cortex M0+ device with different RAM sections, adapt the RAM sections accordingly in the Keil project settings:

CortexM0+ RTT RAMSettings.PNG

  • Build(F7) the project and start debugging by clicking on the Debug button (Ctrl + F5)
  • Start RTT Viewer and connect with the following settings:

RTT Viewer Settings

  • Running the ramcode (F5) in Keil results in the following output in RTT viewer:

RTT Viewer output

Tested Hardware

SAMD21 XPlained Pro