4WD UART

CH344Q based quad isolated USB-UART interface with ESP programmer.

Features | Specs

• 4 fully isolated channels
  • Channel 0 - 2: classic UART with TX, RX, DTR and RTS signals
  • Channel 3: UART + ESP8266/ESP32 programmer signals (EN + IO0) and isolated 3.3V supply
• individual TX/RX activity indicators per channel
• theoretical max baud rate per channel: 6Mbps (tested up to 4.5Mbps on Linux)
• target voltage range: 3V - 5V (required for the isolators)
• USB C for power and data
• optional soft power switch (hold to power on/off) or regular toggle one
• USB inrush current limiter

Leds

Per channel:

• TX, RX - activity leds
• VTG - target power presence

For channel 3:

• 3V3 - internal isolated 3.3V supply enable

Global:

• TX, RX - global CH344Q activity leds
• ACT - USB enumeration success
• PWR - power indicator

Electronic design

Mechanical design

PCB is designed to slide into an 88x100x38mm aluminium extruded enclosure. Front panel and back panel PCBs replace the original plates.

Front panel

Front panel is designed to accommodate the version with soft power switch. A normal pushbutton is used, but installed in reverse with terminals bent, as shown on the pic:

A single 1x02 0.1" SMD type pin header is used to connect the pushbutton to the main board.
Light pipes for the leds can be made by pushing a tiny bit of hot glue into the holes.

Operation

For most modern operating systems the device does not require any special drivers and should be detected automatically.
On Linux 4WD UART is reporting as 4 /dev/TTYACMx devices:

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All channels except 3 (if 3V3 is enabled) require external power supply in range from 3V to 5V to operate the output digital isolators and do the level shifting.

Copyright (c) 2022 by Piotr Zapart
www.hexefx.com

License

This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 International License.