How to see debug output from USB Host?

[Lars Beiderbecke]

I generated a USB Host for HID Class with CubeMX, but when I connect a mouse, its LED at the bottom doesn't light up.

Debugging through USBH_Process(), phost showed the status as HOST_IDLE and CMD_SEND.

To further debug this, I've set the debug level of the USB library to the highest setting and enabled the SWO pin. But how do I actually see any output in TrueStudio? I enabled SWO in the debug configuration, but I'm unsure about the other settings. I've also read somewhere that gdb cannot deal with SWO?!

Any hint or link would be appreciated.