Power Pins:

• Vin - this is the power pin. Since the sensor chip uses 3-5 VDC. To power the board, give it the same power as the logic level of your microcontroller - e.g. for a 5V micro like Arduino, use 5V
• GND - common ground for power and logic

I2C Control-Side pins:

• SCL - this is the I2C clock pin for the chip itself, connect to your microcontrollers I2C clock line.
• SDA - this is the I2C data pin for the chip itself, connect to your microcontrollers I2C data line.
• RST - this is the reset pin, for resetting the multiplexer chip. Pulled high by default, connect to ground to reset.

I2C Address Selection

The default I2C address is 0x70.

• A0 A1 A2 - these are the address selection pins for the multiplexer. By default the multiplexer is at address 0x70 and these three pins are pulled low. Connect them to Vin to set the address to 0x71 - 0x77.
• A0 is the lowest-significant bit (if it is pulled high, it will increase the address by 1).
• A1 is the 2nd-lowest-significant bit (if it is pulled high, it will increase the address by 2).
• A2 is the 3rd-lowest-significant bit (if it is pulled high, it will increase the address by 4).

The default I2C address is 0x70. The other address options can be calculated by “adding” the A0/A1/A2 to the base of 0x70.

A0 sets the lowest bit with a value of 1, A1 sets the next bit with a value of 2 and A2 sets the next bit with a value of 4. The final address is 0x70 + A2 + A1 + A0 which would be 0x77.


So for example if A2 is wired to power and A0 is soldered closed, the address is 0x70 + 4 + 1 = 0x75.


If only A0 is wired to power, the address is 0x70 + 1 = 0x71


If only A1 is wired to power, the address is 0x70 + 2 = 0x72


If only A2 is wired to power, the address is 0x70 + 4 = 0x74

The table below shows all possible addresses, and whether the pin(s) should be high/H (wired to power) or low/L (unconnected).

I2C Multiplexed-Side pins:

• SDx and SCx:  There are 8 sets of SDx and SCx pins, from SD0/SC0 to SD7/SC7. These are the multiplexed pins. Each one is a completely seperate I2C bus set. So you can have 8 I2C devices with identical addresses, as long as they are on one I2C bus each.
  These pins do not have any pullups installed, so if you are using a chip or breakout without i2c pullups be sure to add them! Nicely, you can have Vin be 3.3V and have these pins pulled up to 5V (that is, they are 5V compliant)