Serial Wire Debug (SWD)

Serial Wire Debug (SWD) is a two-wire protocol for accessing the ARM debug interface.

It is part of the ARM Debug Interface Specification v5 and is an alternative to JTAG.

The physical layer of SWD consist of two lines:

• SWDIO: A bidirectional data line.
• SWCLK: A clock driven by the host.

By using SWD interface should be able to program MCUs internal flash memory, access memory regions, add breakpoints, stop/run CPU, etc.

The other good thing about SWD is that you can use the serial wire viewer for your printf() statements for debugging.

2 pin (Debug) + 1 pin (Trace)