以DMA传输方式接收外部串口设备发送的数据并保存到SDRAM存储器中，通过使用串口调试工具来查看数据传输是否正确。-DMA transfer to an external serial device to receive data sent and saved to SDRAM memory, by using the serial port debugging tool to view data transmission is correct.

在STM32板子与电脑串口助手进行通信,用串口的DMA方式,先接收,再发送到PC端,可以连续接收,通过按键一次发送.(In the STM32 board and computer serial assistant for communication, using the serial port DMA way, first receive, and then sent to the PC terminal, you can receive continuously, sent through