The default I2C address is 0x70.

Power Pins

• VIN - this is the power pin. Since the multiplexer 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 Logic Pins - Control

• SCL - I2C clock pin, connect to your microcontroller I2C clock line. This pin is level shifted so you can use 3-5V logic, and there's a 10K pullup on this pin.
• SDA - I2C data pin, connect to your microcontroller I2C data line. This pin is level shifted so you can use 3-5V logic, and there's a 10K pullup on this pin.

I2C Logic Pins - Multiplexed

There are 4 sets of SDA and SCL pins, from SD0/SC0 to SD3/SC3. These are the multiplexed pins. Each one is a completely separate I2C bus set. You can have 4 I2C devices with identical addresses, as long as they are on one I2C bus each. 

Address Pins

On the back of the board are three address jumpers, labeled A0, A1, and A2, next to the lower mounting hole. These jumpers allow you to chain up to 8 of these boards on the same pair of I2C clock and data pins. To do so, you solder the jumpers "closed" by connecting the two pads.

On the front of the board are three address pins, labeled A0, A1 and A2. Just like the jumpers, these pins allow you to change the I2C address to connect multiple boards by connecting them to VIN.

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 soldered closed and A0 is soldered closed, the address is 0x70 + 4 + 1 = 0x75.


If only A0 is soldered closed, the address is 0x70 + 1 = 0x71


If only A1 is soldered closed, the address is 0x70 + 2 = 0x72


If only A2 is soldered closed, the address is 0x70 + 4 = 0x74

The table below shows all possible addresses, and whether the pin(s) should be high (closed) or low (open).

Reset Pin

• RST - Reset pin for resetting the multiplexer chip. Pulled high by default, connect to ground to reset.

I2C Pullup Jumpers

On the back of the board, directly below the Adafruit logo on the silkscreen, are two jumpers located next to the SCL and SDA control pins. You can cut these jumpers to disable to 10K pullup on each pin.

Old Version with Incorrect Labeling

The SCL/SDA output pins were incorrectly labeled on the first production run. If you happen to have a version with these pin labels, use this info to determine the proper output pin names.