How to Use Bi-Directional Logic Level Converter: Examples, Pinouts, and Specs

The Bi-Directional Logic Level Converter is a compact and versatile device designed to enable safe and effective communication between two circuits operating at different voltage levels. It is particularly useful when interfacing low-voltage microcontrollers (e.g., 3.3V) with higher-voltage peripherals (e.g., 5V). This component supports bi-directional signal conversion, making it ideal for applications where data needs to flow in both directions.

• Interfacing 3.3V microcontrollers (e.g., ESP32, Raspberry Pi) with 5V devices (e.g., Arduino, sensors).
• Communication between I2C, SPI, or UART devices operating at different voltage levels.
• Safeguarding low-voltage devices from damage caused by higher voltage signals.
• Prototyping and development of mixed-voltage systems.

The Bi-Directional Logic Level Converter typically consists of four channels, allowing for the conversion of up to four signals simultaneously. Below are the key technical details:

• Voltage Range (High Side): 3.3V to 5.5V
• Voltage Range (Low Side): 1.8V to 3.3V
• Maximum Data Rate: ~100 kHz (I2C) or higher for other protocols
• Channels: 4 independent bi-directional channels
• Dimensions: ~15mm x 15mm (varies by manufacturer)

The Bi-Directional Logic Level Converter typically has the following pin layout:

Note: Some modules may label the channels as TX and RX or simply as 1, 2, 3, and 4. Always refer to the specific module's datasheet for exact pin labeling.

1. Power the Converter:

   • Connect the HV pin to the high-voltage source (e.g., 5V).
   • Connect the LV pin to the low-voltage source (e.g., 3.3V).
   • Connect the GND pin to the common ground of both circuits.

2. Connect the Signal Lines:

   • For each signal to be converted, connect the high-voltage side to the corresponding TX pin and the low-voltage side to the corresponding RX pin (or vice versa, depending on the direction of communication).

3. Verify Connections:

   • Ensure that the voltage levels on the HV and LV pins match the operating voltages of the connected devices.
   • Double-check the ground connection to avoid communication errors.

• Voltage Compatibility: Ensure that the high and low voltage levels fall within the supported ranges of the converter.
• Data Rate Limitations: For high-speed communication protocols, verify that the converter can handle the required data rate.
• Pull-Up Resistors: Some I2C applications may require external pull-up resistors on the signal lines. Check your circuit requirements.
• Avoid Overloading: Do not exceed the maximum current rating of the converter.

Below is an example of using the Bi-Directional Logic Level Converter to interface a 3.3V sensor with a 5V Arduino UNO via I2C.

• HV: Connect to Arduino's 5V pin.
• LV: Connect to the sensor's 3.3V pin.
• GND: Connect to the common ground of the Arduino and the sensor.
• TX1/RX1: Connect to Arduino's SDA pin and the sensor's SDA pin.
• TX2/RX2: Connect to Arduino's SCL pin and the sensor's SCL pin.

#include <Wire.h> // Include the Wire library for I2C communication

void setup() {
  Wire.begin(); // Initialize I2C communication
  Serial.begin(9600); // Start serial communication for debugging
  Serial.println("I2C Communication Initialized");
}

void loop() {
  Wire.beginTransmission(0x40); // Start communication with the sensor at address 0x40
  Wire.write(0x00); // Send a command or register address to the sensor
  Wire.endTransmission(); // End the transmission

  Wire.requestFrom(0x40, 2); // Request 2 bytes of data from the sensor
  if (Wire.available() == 2) { // Check if 2 bytes are available
    int data = Wire.read() << 8 | Wire.read(); // Read and combine the 2 bytes
    Serial.print("Sensor Data: ");
    Serial.println(data); // Print the sensor data to the Serial Monitor
  }

  delay(1000); // Wait for 1 second before the next reading
}

Note: Replace 0x40 with the actual I2C address of your sensor.

1. No Communication Between Devices:

   • Verify that the HV and LV pins are connected to the correct voltage sources.
   • Ensure that the ground connection is shared between all devices.

2. Signal Distortion or Noise:

   • Check for loose or poor-quality connections.
   • Add pull-up resistors to the signal lines if required (e.g., for I2C).

3. Overheating of the Converter:

   • Ensure that the current drawn by the connected devices does not exceed the converter's rating.
   • Double-check the voltage levels on the HV and LV pins.

4. Data Transmission Errors:

   • Verify the data rate of the communication protocol. If it's too high, consider reducing it.
   • Check for proper termination of signal lines in long-distance communication.

Q: Can I use the Bi-Directional Logic Level Converter for SPI communication?
A: Yes, the converter can be used for SPI communication. However, ensure that the data rate and voltage levels are within the supported range.

Q: Do I need external pull-up resistors for I2C?
A: Some modules include built-in pull-up resistors, but if your circuit requires stronger pull-ups, you may need to add external resistors (e.g., 4.7kΩ).

Q: Can I use this converter with 1.8V devices?
A: Yes, as long as the low-voltage side is powered at 1.8V and the high-voltage side is within the supported range (e.g., 3.3V to 5V).

Q: What happens if I reverse the HV and LV connections?
A: Reversing the connections can damage the converter or connected devices. Always double-check your wiring before powering the circuit.