For my breadboarded test rig, I used a four pin Harwin M20 connector. Even on a half size micromouse, this will not take up much room and I may use it as the only debug/programming connector.

The pins on the 20-pin standard JTAG connector to use are:

Pin 1 – VCC:

This is the traget board Vcc. It is used by the STLINK/V2

Pin 7 – TMS/SWDIO:

The SWD Data signal

Pin 8 – GND:

Be sure there is a common ground

Pin 9 – TCK/SWCLK

The SWD Clock Signal

Pin 15 – nSRST/RESET

System reset – probably optional(你可以不要这个复位pin，直接关电源再上电来复位)

ST-Link/V2 JTAG/SWD接口定义 ：

可以自己做一些转接PCB板子，现在USB四线的可以用起来。做一个现在智能手机usb接口，接四根线就好。

SWD不单单可以下载还可以单步调试，速度比JTAG快。有人问，那为什么要发明JTAG这个20pin的接口呢？因为JTAG标准制定不是为了下载程序调试程序用的 ，它用来做“边界扫描”用的，什么是边界扫描不知道的可以 搜搜一些，在国内谷歌需要翻墙软件才好用。百度搜索专业术语类不好用，最近我发现好多东西搜搜比百度好用不少。