SWO

SWO

When introducing the SWD interface, ARM also introduced an optional extension for SWD, called Serial Wire Output (SWO). SWO specifies a dedicated pin, in addition to the debug signals of the SWD interface, which allows the target CPU to output specific data like printf output on a dedicated pin via UART or Manchester protocol. This pin is unidirectional, so it is not possible to send data to the target CPU on this pin.

The Instrumentation Trace Macrocell (ITM) and Serial Wire Output (SWO) can be used to form a Serial Wire Viewer (SWV). The Serial Wire Viewer provides a low cost method of obtaining information from inside the MCU.

Note: Not all targets that support SWD also support SWO. Moreover, SWO is not supported by all CPU architectures that support SWD.