How to Use Gravity 1-8 I2C Multiplexer: Examples, Pinouts, and Specs

The Gravity 1-8 I2C Multiplexer by DFRobot is a versatile device designed to expand the capabilities of a single I2C bus. It allows up to eight I2C devices to be connected and managed simultaneously, even if they share the same I2C address. This is achieved by dynamically switching between the connected devices, ensuring seamless communication without address conflicts.

• Connecting multiple sensors or modules with identical I2C addresses.
• Expanding the I2C bus for complex projects with multiple peripherals.
• Prototyping and testing multiple I2C devices in parallel.
• Robotics, IoT, and automation systems requiring multiple I2C devices.

• Manufacturer Part ID: Gravity I2C Multiplexer
• Operating Voltage: 3.3V to 5V
• I2C Address: Configurable (default: 0x70)
• Number of Channels: 8
• Communication Protocol: I2C
• Dimensions: 42mm x 32mm
• Mounting: Gravity-compatible interface

The Gravity 1-8 I2C Multiplexer has the following pin layout:

1. Power the Module: Connect the VCC pin to a 3.3V or 5V power source and the GND pin to ground.
2. Connect the I2C Bus: Attach the SDA and SCL pins to the corresponding I2C lines of your microcontroller (e.g., Arduino UNO).
3. Connect I2C Devices: Attach up to eight I2C devices to the CH0 to CH7 channels. Ensure proper wiring for power and ground.
4. Select a Channel: Use I2C commands to select the desired channel for communication. Only one channel can be active at a time.

• Address Conflicts: The multiplexer resolves address conflicts by isolating devices on different channels. Ensure devices with the same address are connected to separate channels.
• Pull-Up Resistors: The module includes onboard pull-up resistors for the I2C bus. Avoid adding additional pull-ups unless necessary.
• I2C Address Configuration: The default I2C address is 0x70. If multiple multiplexers are used, configure their addresses using the onboard solder pads.

Below is an example of how to use the Gravity 1-8 I2C Multiplexer with an Arduino UNO:

#include <Wire.h>

// Default I2C address of the multiplexer
#define MULTIPLEXER_ADDR 0x70

// Function to select a specific channel (0-7)
void selectChannel(uint8_t channel) {
  if (channel > 7) return; // Ensure channel is within range
  Wire.beginTransmission(MULTIPLEXER_ADDR);
  Wire.write(1 << channel); // Activate the desired channel
  Wire.endTransmission();
}

void setup() {
  Wire.begin(); // Initialize I2C communication
  Serial.begin(9600); // Initialize serial communication for debugging

  Serial.println("Initializing I2C Multiplexer...");
  selectChannel(0); // Select channel 0 as an example
  Serial.println("Channel 0 selected.");
}

void loop() {
  // Example: Communicate with a device on channel 0
  selectChannel(0); // Ensure channel 0 is active
  Wire.beginTransmission(0x40); // Replace 0x40 with your device's I2C address
  Wire.write(0x00); // Example command
  Wire.endTransmission();

  delay(1000); // Wait for 1 second
}

1. I2C Devices Not Responding:

   • Ensure the correct channel is selected using the selectChannel() function.
   • Verify the wiring of the I2C devices, including power and ground connections.
   • Check for address conflicts if multiple devices are connected.

2. Multiplexer Not Detected:

   • Confirm the I2C address of the multiplexer (default: 0x70).
   • Use an I2C scanner sketch to detect the multiplexer and connected devices.

3. Communication Errors:

   • Ensure the I2C bus voltage matches the operating voltage of the connected devices.
   • Check for loose or faulty connections in the circuit.

Q: Can I use multiple multiplexers in the same project?
A: Yes, you can use multiple multiplexers by configuring their I2C addresses using the onboard solder pads.

Q: Can I activate multiple channels simultaneously?
A: No, the multiplexer allows only one channel to be active at a time to prevent address conflicts.

Q: Do I need external pull-up resistors?
A: The module includes onboard pull-up resistors. Additional pull-ups are generally not required unless specified by your circuit design.