SWO on FRDM-MCXN947 Pauses Under Debug Mode

kaosad — Wed, 19 Aug 2026 07:47:35 GMT

I followed this useful guide: ITM vs. UART Printing on MCUXpresso IDE. At first, I thought it wasn’t working because nothing appeared on the SWO ITM Console. Soon, I realized that the SWO pauses during active debugging. I have to press Resume (F8) just to see the output. This is frustrating because I cannot view log prints in real time while stepping through code. How can I fix this limitation?

Re: SWO on FRDM-MCXN947 Pauses Under Debug Mode

Harry_Zhang — Fri, 21 Aug 2026 10:05:22 GMT

Hi @kaosad

With ITM/SWO, data is generated and transmitted by the running target. When you hit a breakpoint or single-step, the Cortex-M core is halted, so the application stops executing and no new printf() / ITM_SendChar() calls occur. As a result, the SWO ITM Console only receives new messages while the MCU is running.

When you press Resume, the target runs again and the ITM hardware can stream trace data over SWO in real time. MCUXpresso's SWO mechanism is designed to capture events from a running MCU without interrupting execution.

Harry

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SWO on FRDM-MCXN947 Pauses Under Debug Mode

Re: SWO on FRDM-MCXN947 Pauses Under Debug Mode