因为我的L053板子有点问题，没法用mbed的串口调试程序。

所以只能自己接串口模块连接电脑。

比较坑爹的是，nucleo板子上TX和RX的两个引脚，默认是不和MCU相连接的……

如果想要使用两个引脚，需要将板子背面的SB62和SB63相连接（焊一下）。

这个东西在ST给的文档里有说明，下载地址，在这个网页下方有很多相关的文档。比较详细的是UM1724这个pdf。

“The USART2 interface available on PA2 and PA3 of the STM32 microcontroller can be connected to ST-LINK MCU, STMicroelectronics Morpho connector or to Arduino connector. The choice can be changed by setting the related solder bridges. By default the USART2 communication between the target MCU and ST-LINK MCU is enabled in order to support Virtual Com Port for mbed (SB13 and SB14 ON, SB62 and SB63 OFF). If the communication between the target MCU PA2 (D1) or PA3 (D0) and shield or extension board is required, SB62 and SB63 should be ON, SB13 and SB14 should be OFF. In such case it possible to connect another USART to ST-LINK MCU using flying wires between Morpho connector and CN3.”

ST nucleo板子外接串口调试方法