SWO outputs only works with HSI enabled for SYSCLK, not HSE

[mangobay11]

Hi,

I am using a STM32F105RC. I was trying to get SWO printf outputs to work, and found that they only work when I configure HSI (8MHz) to be used for SYSCLK, but not when I configure HSE (25MHz) for SYSCLK. I've confirmed that the external oscillator itself is correct.

Any ideas would be appreciated, Thanks!

[TDK]

You'll have to configure the SWV viewer clock rate to match your system clock. In STM32CubeIDE, this is done in the debug configuration window.

[mangobay11]

Hi TDK, thanks for the reply.

I am using OpenOCD. I found that the SWO clock frequency was not set correctly, but I don't understand why.

Anyways, with a core clock frequency of 25MHz and a SWO clock frequency of 2.25MHz I am able to view SWO output