How to Use USB to UART adapter: Examples, Pinouts, and Specs

The USB to UART adapter is a versatile electronic component that bridges the gap between USB interfaces and UART (Universal Asynchronous Receiver-Transmitter) communication. It enables seamless communication between a computer's USB port and serial devices, such as microcontrollers, sensors, and embedded systems. This adapter is widely used in prototyping, debugging, and programming applications.

• Programming and debugging microcontrollers (e.g., Arduino, ESP32, STM32)
• Interfacing with serial devices like GPS modules, GSM modules, and sensors
• Data logging and communication with embedded systems
• Serial communication testing and monitoring
• Connecting legacy serial devices to modern computers

• Input Interface: USB 2.0/3.0 (Type-A or Type-C, depending on the model)
• Output Interface: UART (TX, RX, GND, and optionally CTS/RTS)
• Supported Baud Rates: 300 bps to 3 Mbps (varies by chipset)
• Chipset: Commonly FTDI FT232, CP2102, CH340, or PL2303
• Voltage Levels: 3.3V or 5V (selectable on some models)
• Operating Temperature: -40°C to 85°C
• Power Supply: Powered via USB (5V)

The USB to UART adapter typically has the following pin configuration:

1. Connect the Adapter to Your Computer:

   • Plug the USB connector of the adapter into an available USB port on your computer.
   • Install the necessary drivers for the adapter's chipset (e.g., FTDI, CP2102, CH340, or PL2303). Drivers are typically available on the manufacturer's website.

2. Connect the Adapter to the Target Device:

   • Connect the TXD pin of the adapter to the RXD pin of the target device.
   • Connect the RXD pin of the adapter to the TXD pin of the target device.
   • Connect the GND pin of the adapter to the GND pin of the target device.
   • If required, connect the VCC pin to power the target device (ensure voltage compatibility).

3. Configure the Serial Communication:

   • Open a serial terminal program (e.g., PuTTY, Tera Term, or Arduino IDE Serial Monitor).
   • Select the correct COM port assigned to the adapter.
   • Set the baud rate and other serial parameters (e.g., data bits, stop bits, parity) to match the target device.

4. Test the Connection:

   • Send and receive data to verify communication between the computer and the target device.

• Voltage Compatibility: Ensure the adapter's voltage level (3.3V or 5V) matches the target device to avoid damage.
• Driver Installation: Install the correct driver for the adapter's chipset to ensure proper functionality.
• Cross TX and RX: Always connect the adapter's TXD to the target device's RXD and vice versa.
• Avoid Overloading: Do not draw excessive current from the adapter's VCC pin; it is typically limited to a few hundred milliamps.
• Use Hardware Flow Control (if needed): For devices requiring hardware flow control, connect the RTS and CTS pins appropriately.

The USB to UART adapter can be used to program or communicate with an Arduino UNO. Below is an example of Arduino code to test serial communication:

// Example: Echo received data back to the sender
// This code reads data from the serial port and sends it back.

void setup() {
  Serial.begin(9600); // Initialize serial communication at 9600 baud
  while (!Serial) {
    // Wait for the serial port to connect (for boards like Arduino Leonardo)
  }
  Serial.println("USB to UART Adapter Test");
}

void loop() {
  if (Serial.available() > 0) {
    char receivedChar = Serial.read(); // Read a character from the serial port
    Serial.print("Received: ");        // Print the received character
    Serial.println(receivedChar);
  }
}

1. Can I use the adapter with a 1.8V device?

   • Most adapters support 3.3V or 5V logic levels. For 1.8V devices, use a level shifter.

2. How do I find the COM port assigned to the adapter?

   • On Windows, check the Device Manager under "Ports (COM & LPT)." On macOS/Linux, use the ls /dev/tty* command to locate the device.

3. What is the maximum cable length for the adapter?

   • USB cables are typically limited to 5 meters. For longer distances, use a USB repeater or active extension cable.

4. Can I use the adapter for SPI or I2C communication?

   • No, the adapter is designed for UART communication only. Use a dedicated USB-to-SPI or USB-to-I2C adapter for those protocols.

By following this documentation, you can effectively use a USB to UART adapter for a wide range of serial communication tasks.