![]() Because the SWO trace output clock is derived from the CPU clock, the Init function needs that clock plus which SWO port number to be initialized. My recommendation is to initialize it from the application. □ An example project with all the sources is available on GitHub: Įxternal tools (like the Segger RTT viewer) can set up the SWO in the hardware. #Segger embedded studio real time terminal codeIn order to write debug message over SWO to the host, a small piece of code is needed. J-link-edu-connected-to-trace-port Source Code to Send Debug Messages over SWO Trace Pin SWO is part of the ARM CoreSight Debug block which usually is part of Cortex-M3, M4 and M7: There would be another encoding (Manchester encoded) which is not covered here. And this is what I’m going to show in this article. One of the most common usage is the first one: using SWO to print debug messages from the target in UART style. Variable or memory cell change over time.What kind of data is sent is up to the application, and there is only very little CPU processing or code needed. Up to 32 packet types (or stimulus) can be used. So make sure that SWD is selected as debugging protocol: swd-debug. SWO only is supported in SWD (Single Wire Debug) mode, and not in JTAG mode. You can think of SWO as a kind of UART TX pin using a special format to send out data packets. To receive the SWO trace output on the host, the GNU ARM Eclipse plugins have built-in SWO support for the Segger J-Link probes. Technically SWO is a single trace pin which is used to stream out data packets with a certain clock rate, derived from the CPU core clock. ARM SWOīut there is yet another thing: ARM SWO trace port as defined by ARM for Cortex-M. But works only with Segger debugging probes. There is Segger RTT which is small, fast and best of all does not need any special pins. There is USB CDC, but this requires a USB connector, a USB stack and a microcontroller capable of USB. There is semihosting, but this is very slow, depends on the debugger and toolchain/library used plus is a wast of FLASH and RAM so I don’t recommend using semihosting at all. ![]() However, on many boards the UART’s are used by the application. As the standard text and command line interface to my target boards I’m using a normal UART/SCI. ![]()
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