USB to UART

USB to UART Converter (CH340G)

A compact USB-to-UART adapter based on the CH340G, implemented as a USB-A edge connector board. Fabrication files have been generated; board fabrication is pending.

Overview

This project implements a reliable USB-to-UART interface suitable for development, debugging, and embedded bring-up tasks. Unlike typical breakout boards, this design uses a USB-A edge connector, allowing direct insertion into a host USB port without a cable.

The board supports both 5 V and 3.3 V UART logic levels via jumper selection.

Key Features

• CH340G USB-to-UART bridge
• USB-A edge connector (ENIG finish, bevelled)
• Jumper-selectable UART logic level (5 V / 3.3 V)
• On-board 3.3 V LDO
• USB ESD protection
• Polyfuse on VBUS for over-current protection
• Status LEDs (Power, TX, RX)
• RTS / CTS / DTR / DSR signals exposed
• 2-layer PCB, 1.6 mm thickness

Design Tools Used

• KiCad (schematic capture, PCB layout, Gerber generation)

Design Highlights

• Grounding strategy

  • Ground stitching vias near USB connector, ESD, and IC
  • Controlled return paths for high-speed signals

• Clock integrity

  • 12 MHz crystal placed close to XI/XO pins
  • Symmetric routing and tight loop area
  • Dedicated ground vias for crystal capacitors

• Manufacturability

  • ENIG finish selected for USB edge reliability
  • Bevelled edge specified for connector durability
  • Clean DRC-verified Gerber output

Repository Structure

usb-to-uart-ch340g-pcb/
├── README.md
├── LICENSE
├── docs/
│   ├── images/
│   └── design-notes.md
├── schematic/
│   └── usb-to-uart-ch340g_schematic.pdf
├── pcb/
│   └── layout_screenshots/
├── fabrication/
│   ├── USB-to-UART-CH340G_Gerbers.zip
│   └── fab-notes.txt
├── datasheet/
│   └── CH340G_datasheet.pdf
└── KiCAD files/
    ├── usb-to-uart.kicad_pro
    ├── usb-to-uart.kicad_sch
    ├── usb-to-uart.kicad_prl
    └── usb-to-uart.kicad_pcb

Fabrication Details

• Layers: 2
• Board thickness: 1.6 mm
• Copper weight: 1 oz
• Surface finish: ENIG
• USB edge connector: bevelled
• Solder mask: standard

References and Attribution

• The USB-A edge connector footprint is adapted from an open-source KiCad footprint library. The original library is referenced here for attribution: https://github.com/vasya-zh/PCB-Edge-USB-connector-KiCad-library

• Component selection and implementation follow the WCH CH340G datasheet and standard USB Full-Speed design guidelines.

• Some YouTube tutorials and online articles on USB-to-UART designs were consulted during development.
  PCB Cupid
  Hardik Seth
  Electronics Globe

License

This project is released under the MIT License unless stated otherwise. Third-party references retain their respective licenses.

Notes

This project was built as a practical hardware design exercise, with emphasis on finishing a complete, manufacturable PCB rather than producing a minimal demo board. Future revisions may explore USB-C support or auto-voltage sensing.