The default I2C address is 0x50.

Power Pins

  • VIN - this is the power pin. Since the EEPROM chip may use 3 VDC, we have included a voltage regulator on board that will take 3-5VDC and safely convert it down. To power the board, give it the same power as the logic level of your microcontroller - e.g. for a 5V microcontroller like Arduino, use 5V.
  • 3V - this is the 3.3V output from the voltage regulator, you can grab up to 100mA from this if you like.
  • GND - common ground for power and logic.

I2C Logic Pins

  • 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.
  • STEMMA QT - These connectors allow you to connectors to dev boards with STEMMA QT connectors or to other things with various associated accessories.

Address Pins

On the back of the board are three address jumpers, labeled A0, A1, and A2. 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 0x50. The other address options can be calculated by “adding” the A0/A1/A2 to the base of 0x50.

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 0x50 + A2 + A1 + A0 which would be 0x57.


So for example if A2 is soldered closed and A0 is soldered closed, the address is 0x50 + 4 + 1 = 0x55.


If only A0 is soldered closed, the address is 0x50 + 1 = 0x51


If only A1 is soldered closed, the address is 0x50 + 2 = 0x52


If only A2 is soldered closed, the address is 0x50 + 4 = 0x54

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

Write-Protect Pin

  • WP - Write-protect pin. Connect to VCC to make the EEPROM read-only.

Power LED

  • Power LED - In the upper left corner, above the STEMMA connector, on the front of the board, is the power LED, labeled on. It is the green LED.

This guide was first published on Sep 20, 2022. It was last updated on Jun 22, 2024.

This page (Pinouts) was last updated on Mar 08, 2024.

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