How to Use 4-Channel Bi-Directional Logic Level Shifter: Examples, Pinouts, and Specs

The 4-Channel Bi-Directional Logic Level Shifter (Manufacturer Part ID: BSS138 Level Shifter Module) is a compact and versatile device designed to facilitate communication between electronic components operating at different voltage levels. It enables seamless bi-directional data transfer across four independent channels, making it an essential tool for interfacing low-voltage microcontrollers (e.g., 3.3V) with higher-voltage peripherals (e.g., 5V).

• Interfacing 3.3V microcontrollers (e.g., ESP32, Raspberry Pi) with 5V sensors or modules.
• Enabling communication between 1.8V, 3.3V, and 5V devices in mixed-voltage systems.
• Level shifting for I2C, SPI, UART, and other digital communication protocols.
• Prototyping and development of mixed-voltage circuits.

The following table outlines the key technical details of the 4-Channel Bi-Directional Logic Level Shifter:

The module has 8 pins, divided into two voltage domains: High Voltage (HV) and Low Voltage (LV). The table below describes each pin:

1. Power Connections:

   • Connect the HV pin to the higher voltage power supply (e.g., 5V).
   • Connect the LV pin to the lower voltage power supply (e.g., 3.3V).
   • Connect the GND pin to the common ground of the circuit.

2. Data Connections:

   • For each channel, connect the high-voltage signal to the corresponding HVx pin.
   • Connect the low-voltage signal to the corresponding LVx pin.
   • Repeat for all channels as needed.

3. Communication Protocols:

   • The module supports I2C, SPI, UART, and other digital protocols. Ensure proper pull-up resistors are used for I2C communication.

• Voltage Compatibility: Ensure the voltage levels on the HV and LV sides match the specifications of the connected devices.
• Pull-Up Resistors: For I2C communication, use appropriate pull-up resistors on both the HV and LV sides.
• Data Rate: The module is suitable for low- to medium-speed communication (e.g., ~100 kHz for I2C). For higher speeds, verify signal integrity.
• Common Ground: Always connect the ground of the module to the ground of all connected devices.

Below is an example of using the level shifter 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.
• HV1, HV2: Connect to Arduino's SDA and SCL pins, respectively.
• LV1, LV2: Connect to the sensor's SDA and SCL pins, respectively.

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

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

void loop() {
  // Example: Request data from a 3.3V sensor at address 0x40
  Wire.beginTransmission(0x40); // Start communication with the sensor
  Wire.write(0x00); // Send a command or register address
  Wire.endTransmission(); // End transmission

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

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

1. No Communication Between Devices:

   • Verify that the HV and LV pins are connected to the correct voltage levels.
   • Ensure the ground of all devices is connected to the module's GND pin.
   • Check for proper pull-up resistors on I2C lines.

2. Data Corruption or Signal Loss:

   • Reduce the data rate if operating at high speeds.
   • Ensure the signal lines are not too long, as this can cause signal degradation.

3. Overheating or Damage:

   • Double-check that the voltage levels do not exceed the module's specifications.
   • Avoid short circuits between HV and LV pins.

Q: Can this module be used for analog signals?
A: No, the module is designed for digital signals only. It is not suitable for analog signal level shifting.

Q: What is the maximum voltage supported on the HV side?
A: The HV side supports a maximum voltage of 5V. Exceeding this may damage the module.

Q: Can I use fewer than four channels?
A: Yes, you can use as many or as few channels as needed. Unused channels can be left unconnected.

Q: Does the module require external power?
A: No, the module is powered directly from the HV and LV voltage inputs.

By following this documentation, you can effectively integrate the 4-Channel Bi-Directional Logic Level Shifter into your projects and ensure reliable communication between devices operating at different voltage levels.