Programming USB Port Labels

This procedure applies to optional USB ports added to the P4 Node Adapter using CH340C devices behind a CH334R USB hub.

It allows the builder to assign human-readable USB port names (Product Strings) and unique serial numbers so Windows can clearly identify each port.

Scope and Important Notes

  • This procedure applies only to:
    • CH340C devices installed on the P4 Node Adapter
  • This does not apply to:
    • The Waveshare P4 board’s built-in USB port (see note below)

Builder note
This is a one-time configuration step typically done during assembly or initial bring-up.

About the Waveshare P4 Built-In USB Port

The Waveshare P4 board includes its own onboard USB-to-UART converter, factory programmed by the manufacturer.

  • ✔ It already has valid USB descriptors
  • ✔ It does not require labeling for normal use
  • ❌ It is not reprogrammed as part of this procedure
  • ❌ Its USB descriptor is typically not user-configurable

Only the optional CH340C devices added on the adapter are programmed.

Required Tool (Windows)

Download and install the official WCH configuration utility:

CH34xSerCfg – USB Descriptor Configuration Tool
https://www.wch-ic.com/downloads/CH34xSerCfg_ZIP.html

  • Windows-only
  • GUI-based
  • Official WCH utility

Hardware Prerequisites

Depending on the selected build option:

  • CH334R USB hub installed
  • 1–3 × CH340C USB-to-UART devices installed
  • Corresponding slide switches installed and functional
  • Adapter connected to a Windows PC via USB

Slide Switch Usage (Critical)

Each CH340C port includes a dedicated slide switch that controls whether that device is connected to the USB hub.

Rules

  • Only one slide switch may be ON at a time during programming
  • All other CH340C switches must be OFF
  • This ensures the configuration tool talks to exactly one device

There are no jumpers and no bypass paths.

Use the following values consistently:

Function Product String Serial Number
Serial Console Node Console P4-CONSOLE
CAN Bridge SLCAN Bridge P4-SLCAN
ESP32-C6 Flash C6 Flash P4-C6FLASH

Serial numbers must be unique across all CH340C devices.

Programming Procedure (Repeat Per CH340C)

Step 1 – Disable All Ports

Set all CH340C slide switches to OFF.

Step 2 – Enable One Port

Turn ON exactly one slide switch corresponding to the CH340C you want to program.

Step 3 – Launch Configuration Tool

  1. Run CH34xSerCfg.exe
  2. Right-click → Run as Administrator
  3. Click Read to load current device data

If no device is detected:

  • Verify only one switch is ON
  • Replug USB

Step 4 – Set USB Descriptor Fields

Edit only the following fields:

  • Product String
    • Example: SLCAN Bridge
  • Serial Number
    • Example: P4-SLCAN

⚠ Do not change:

  • VID
  • PID
  • Power parameters

Step 5 – Write Configuration

  1. Click Write
  2. Wait for success confirmation
  3. Turn the slide switch OFF
  4. Unplug and replug USB (recommended)

Step 6 – Repeat

Repeat Steps 2–5 for each remaining CH340C port.

Verification

After all ports are programmed:

  1. Turn all slide switches ON
  2. Open Windows Device Manager
  3. Expand Ports (COM & LPT)

You should see entries similar to:

  • USB-SERIAL CH340 (Node Console) (COMx)
  • USB-SERIAL CH340 (SLCAN Bridge) (COMy)
  • USB-SERIAL CH340 (C6 Flash) (COMz)

COM numbers may vary.

Troubleshooting

Multiple devices appear in the tool

  • More than one slide switch is ON

No device appears

  • Slide switch OFF
  • USB cable disconnected
  • Driver not installed

Wrong label applied

  • Re-enable that port’s switch and repeat the procedure

Summary

  • The CH334R hub does not assign port identities
  • Each CH340C must be labeled individually
  • Slide switches provide deterministic, builder-controlled selection
  • This avoids jumpers, firmware tricks, and guesswork
  • USB / Serial Build Configuration Options
  • SLCAN Bridge Usage Guide
  • ESP32-C6 Flashing Guide
Last updated on: February 05, 2026 © 2026 Pat Fleming