Ch340 – Hardware details

Pinout

USB-UART CH340 converter pinout diagram

Click here for a high-resolution image of the pinout.

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Pin Details

⚠️

Mandatory pins for basic operation are VCC, GND, RXD and TXD.

Pin Marking	Pin Name	Description
VCC	Power Input	Main power (3V3 or 5V depending on the board switch) input for the CH340 module.
GND	Ground	Common ground for all signals and power connections.
RXD	Receive Data	Serial data input (data received from the USB host or external device).
TXD	Transmit Data	Serial data output (data sent to the USB host or external device).

ℹ️

Optional pins for additional features are 3V3, 5V and R232.

Pin Marking	Pin Name	Description
3V3	3.3V Output	Provides a 3.3V output from the CH340, useful for powering low-voltage circuits.
5V	5V Output	Provides a 5V output, typically used to power external devices.
R232	RS-232 Signal	Used for RS-232 communication (specific function depends on implementation).

ℹ️

Hardware flow control pins (CTS, RTS, DTR, DSR, DCD) can be used for advanced serial communication.

Pin Marking	Pin Name	Description
CTS	Clear to Send	Hardware flow control signal, used to indicate when data can be sent.
RTS	Request to Send	Hardware flow control signal, used to request data transmission.
DTR	Data Terminal Ready	Signals that the device is ready to communicate.
DSR	Data Set Ready	Indicates that the device is ready to receive data.
DCD	Data Carrier Detect	Detects the presence of a connected device in serial communication.

⚠️

Make sure you're using a data-capable USB cable. Some USB cables only provide power and do not support data transfer.

⚠️

Ensure that GND is properly connected to establish a common reference for all signals.

⚠️

Ensure that RXD (Receive) is connected to TXD (Transmit) on the target device, and TXD is connected to RXD. Incorrect wiring will result in no communication.

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Jumper Details

This board contains hardware jumpers. See below for their locations and functions:

JP1 on the board

Jumper	Default State	Function
JP1	NC (Normally closed)	When closed, enables the PWR LED.

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Voltage Selection Switch

Used to select the 5V or 3V3 power supply on the VCC pin.

Voltage switch on the board

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Dimensions

• Board Dimensions: 38 × 22 mm (1.5 × 0.9 inch)
• Header Pin Holes: 1.5 mm
• Screw Holes: Designed for M3 screws (3.2 mm diameter)
• Soldered boards are LEGO compatible! 🧱

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Hardware repository

Schematics, KiCad files, Gerber files and more can be found in the GitHub repository:

USB-UART CH340 converter board Hardware design

GitHub hardware repository for this product

The hardware repository contains everything you need to understand, modify, or manufacture the board. The different output folders are versioned. You can check which board version you have by looking for the version mark on the PCB.

Below is an overview of the available files.

CAD files

We use KiCad, an open-source PCB design tool. You can open and edit the .kicad_pro project file, which includes both the schematic and PCB layout.

The PANEL files are used internally for production.

Schematic

The OUTPUTS folder contains the schematic in .pdf format, exported from KiCad.

BOM (Bill of Materials)

The bill of materials (BOM) is provided in two formats:

• A standard .csv table, listing all components, part numbers, and values.
• An interactive BOM (.html) that visually highlights each component on the PCB, making it easy to locate and reference parts.

3D files

A 3D model of the PCB is available in .step format, allowing you to inspect the board design in CAD software.

Gerber files

Gerber files are essential for PCB manufacturing, as they contain precise instructions for each layer of the board. The repository includes standard Gerber outputs in a .zip file, such as:

• Copper layers (.Cu.gbr) – Defines the traces and pads on the board.
• Solder mask layers (.Mask.gbr) – Specifies the protective solder mask.
• Silkscreen layers (.Silkscreen.gbr) – Contains text and component markings.
• Paste layers (.Paste.gbr) – Used for stencil fabrication in SMD assembly.
• Drill files (.drl) – Provides drilling coordinates for vias and holes.
• Board outline (.Edge_Cuts.gbr) – Defines the shape of the PCB.
• Gerber job file (.gbrjob) – Describes the set of Gerber files used for production.

These files are ready for fabrication and can be used in PCB manufacturing.

Compliance

The Compliance section includes important regulatory and safety documentation for this product. These files ensure compliance with relevant industry standards and legal requirements.

• CE – Certification document confirming compliance with EU safety, health, and environmental requirements.
• UKCA – UKCA (UK Conformity Assessed) certification for the UK market.
• Safety Instructions – Safety guidelines and precautions in English and in German.
• Info.txt – Contains product details such as SKU, country of origin, HS tariff code, and barcode.