XWLink (DAPlink) based on Air32

This document introduces
a programmer based on the domestically produced AIR32 microcontroller. The casing uses a common USB flash drive casing, currently only available for USB-A ports, and the cost is less than 10 RMB.
Advantages: inexpensive, has a casing, compact, 0805 package.
Disadvantages: no isolation, no ESD protection. The PCB layout
uses horizontal lines on the top layer and vertical lines on the bottom layer, which is convenient for routing. Since JLCPCB provides free four-layer boards, two ground layers are added in the middle, which can be removed without affecting the wiring. The USB differential traces do not pass through vias. It has been tested and can run DAPlinkV2. The code uses open-source DAPLink code, with modifications to the onboard modules to enable flashing LEDs during programming. The code is open-source on GITEE: DAPLINK: Air32 modified DAPLINK project, supporting 216MHz CPU frequency, high-speed serial port and serial flow control, and USB flash drive programming and upgrades (gitee.com). The code is written using RTOS + HAL libraries, facilitating development and portability. It can also program STlink binaries. The tutorial can be found in 012_STLinkV2.1 VCP - JLCPCB EDA Open Source Hardware Platform (oshwhub.com). The speed was compared by burning a 732 KB bin file using KEIL, and the results are as follows. This has some reference value, but inaccuracies are inevitable due to manual speed variations. The test file is attached; you can test it yourself. For serial USB flash drive burning , simply drag and drop the bin file to be burned to the root directory of the USB flash drive.