CH340G USB to TTL Serial Converter Module - 3.3V/5V Logic Programmer

Specifications

• Core IC: WCH CH340G

• USB Interface: Standard USB Type-A Male

• Operating Logic Voltage: 3.3V or 5V (Selectable via physical jumper)

• Pinout: 5V, VCC, 3V3, TXD, RXD, GND

• Baud Rates: 50 bps to 2 Mbps

• Timing: 12.000 MHz External Crystal Oscillator

• LED Indicators: Power, TX Traffic, RX Traffic

• Dimensions: ~45mm x 17mm x 6mm

• Supported OS: Windows (7/10/11), macOS, Linux

Key Applications and Projects

• ESP8266 / ESP32 Flashing: Providing the 3.3V serial interface necessary to upload custom IoT firmware (like Tasmota or ESPHome) to bare ESP-01 modules.

• Headless Raspberry Pi Console: Logging directly into a Raspberry Pi's Linux terminal via its GPIO UART pins when you don't have a monitor or network connection available.

• Router & Modem Unbricking: Connecting to the hidden UART diagnostic headers inside dead Wi-Fi routers to interrupt the bootloader and flash fresh firmware via TFTP.

• GPS Module Interfacing: Testing NMEA sentence outputs from raw GPS modules directly on your PC terminal before integrating them into a microcontroller circuit.

Unlock New Capabilities (Project Evolution) The ESP-01 Mass-Programming Jig: Are you building a swarm of Wi-Fi temperature sensors? Flashing bare ESP-01 modules with loose jumper wires is tedious. Evolve your workflow! Take a small piece of perfboard and solder an 8-pin female header to accept the ESP-01. Wire the RX, TX, and GND to this CH340G module. Add a small tactile push-button bridging the ESP's GPIO0 pin to Ground. Plug the CH340G directly into your PC (set to 3.3V logic!). Now, you can drop an ESP-01 into the socket, hold the button, apply power, and flash your code in seconds. You have just built a factory-style programming jig!

Package Includes:

• 1 x CH340G USB to TTL Serial Converter Module (Black)

• 1 x Yellow 2-Pin Shunt Jumper (Pre-installed)

FREQUENTLY ASKED QUESTIONS (FAQ)

Q: The title says RS232, does this output true RS232 voltage? No. This is a very common marketing misconception. This module outputs TTL (Transistor-Transistor Logic) signals operating at 0V to 5V (or 3.3V). True RS232 operates at -12V to +12V. Do not wire this directly to an old 9-pin RS232 serial port without a MAX232 level-shifting chip in between.

Q: How do I switch between 3.3V and 5V logic? Locate the 3 exposed pins on the side (5V, VCC, 3V3) and the yellow jumper cap. To use 5V logic, place the cap over the 5V and VCC pins. To use 3.3V logic, move the cap to cover the 3V3 and VCC pins.

Q: Does moving the jumper change the TX and RX voltage levels? Yes. The jumper determines the reference voltage for the CH340G chip. Setting it to 3.3V ensures the TX logic level drops to a safe 3.3V.

Q: Do I need to install drivers for the CH340G? Yes. Unlike FTDI chips which are often baked into modern OS updates, you typically need to download and install the official "WCH CH340 Driver" for Windows or macOS for the virtual COM port to appear.

Q: Where is the DTR pin for auto-resetting Arduinos? This specific 6-pin module design does not break out the DTR pin. It is designed purely for standard serial communication and manual flashing.

Q: How do I program an Arduino Pro Mini without a DTR pin? You must reset the board manually. Hold down the physical reset button on your Arduino Pro Mini, click "Upload" in the Arduino IDE, and release the reset button the exact moment the IDE text changes from "Compiling" to "Uploading".

Q: Can I use this to program an ESP8266? Absolutely. Ensure the jumper is strictly set to 3.3V. Connect TX to RX, RX to TX, and GND to GND. Remember that you must manually ground the GPIO0 pin on the ESP module on boot to enter flash mode.

Q: What do the onboard LEDs mean? The PWR-DSP LED illuminates continuously to show the board has USB power. The TXD-DSP flashes when your PC is transmitting data, and the RXD-DSP flashes when the target device replies.

Q: How do I wire the TX and RX pins? Serial data must cross over. Wire the CH340G TX (Transmit) to the target board's RX (Receive). Wire the CH340G RX to the target board's TX.

Q: Is it mandatory to connect the GND pin? Yes! You must always connect the GND pin on this module to the GND of your target microcontroller to establish a common electrical reference, otherwise, the data signals will be garbled.

Q: What is the maximum baud rate supported? The CH340G, supported by the onboard 12MHz crystal, can handle high-speed baud rates up to 2 Mbps.

Q: Can I power my circuit directly from the VCC pin? If set to 5V, the VCC pin can supply up to ~400mA directly from the USB port. If set to 3.3V, the power is drawn from the CH340G's internal low-dropout regulator, which maxes out around 50mA. Do not power heavy loads (like an actively transmitting ESP8266) from the 3.3V pin.

Q: Will this work with a Raspberry Pi? Yes. You can plug it into a PC and wire it to the Raspberry Pi's GPIO UART pins to access the serial console. Just ensure the jumper is set to 3.3V to protect the Pi's logic pins.

Q: What is the silver oval component on the board? That is a 12.000 MHz crystal oscillator. It provides a highly accurate timing heartbeat to the CH340G chip, ensuring serial data packets stay synchronized at high speeds.

Q: My computer says "USB Device Not Recognized", how do I fix this? This almost always indicates a missing driver. Download the latest CH340/CH341 driver package from the WCH website. If it still fails, ensure the module is plugged directly into the PC and not through an unpowered USB hub.

Q: Can I remove the yellow jumper completely? If you remove the jumper cap, the central VCC pin will not output any power, and the logic voltage of the IC may float unpredictably. The jumper must bridge VCC to either 3V3 or 5V for stable operation.

Q: Can I use this with Windows 11? Yes, the latest WCH drivers fully support Windows 11.

Q: Is this compatible with macOS Apple Silicon (M1/M2/M3)? Yes, WCH provides updated, signed drivers for modern macOS architectures, though installation may require approving the driver in your Mac's Security & Privacy settings.

Q: What happens if I accidentally leave it on 5V and connect it to a 3.3V sensor? Sending a 5V signal into a sensor or microcontroller that is strictly rated for 3.3V logic (like a GPS module or an ESP32) will typically cause permanent electrical damage to the target device. Always check the jumper before connecting!

Q: Can I plug dupont jumper wires directly onto these pins? Yes, the 6-pin male header features standard 2.54mm (0.1") pitch spacing, perfectly accommodating standard female-to-female dupont jumper cables.