USB HUB-V3 based on SL2.1A

This project is a USB hub based on the SL2.1A chip. Placing it on an office desk eliminates the need to crawl under the desk to plug in USB drives. Connecting a Bluetooth receiver also makes using a Bluetooth keyboard and mouse more convenient, resulting in a cleaner desktop.
Specific functions include:

expanding one USB port to six ports
; a separate USB port; using a CH340N converter to TTL
serial port for programming; and one-click download support.

Note:

RXD and TXD have already been reversed; do not reverse them when downloading programs.
If you are not soldering a crystal oscillator, you can ground the chip's XI pin.
The switch on the CAD panel file needs to be removed and replaced with an opening. You can buy nylon posts on Taobao to insert, or use a long-handled button.
The USB hole in the panel file can be increased by 1mm; otherwise, it may be difficult to install after printing .

Upgrades:
Future upgrades may include the SL2.2S, adding independent power supply and other protection circuits; the casing may be 3D printed.
After installation: