The default I2C address is 0x20.
- VIN - This is the power pin. To power the board, give it the same power as the logic level of your microcontroller - i.e. for a 5V micro like Arduino, use 5V, or for a 3V micro like a Feather, use 3V.
- GND - This is common ground for power and logic.
- SCL - I2C clock pin, connect to your microcontroller's 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's 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 connect to development boards with STEMMA QT connectors, or to other things, with various associated accessories.
- Along the top are the 8 I/O pins for expanding your project. They are labeled above the pads, left-to-right as P7 through P0.
- On the far left is the positive voltage for the expander I/O pins. It is labeled below the pad with a + in a circle
- On the far right is the ground for the expander I/O pins. It is labeled below the pad with a - in a circle.
- 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 is one address pin, labeled A0. Just like the jumpers, this pin allows you to change the I2C address to connect multiple boards by connecting it to VIN.
The default I2C address is 0x20. The other address options can be calculated by “adding” the A0/A1/A2 to the base of 0x20.
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 0x20 + A2 + A1 + A0 which would be 0x27.
So for example if A2 is soldered closed and A0 is soldered closed, the address is 0x20 + 4 + 1 = 0x25.
If only A0 is soldered closed, the address is 0x20 + 1 = 0x21
If only A1 is soldered closed, the address is 0x20 + 2 = 0x22
If only A2 is soldered closed, the address is 0x20 + 4 = 0x24
The table below shows all possible addresses, and whether the pin(s) should be high (closed) or low (open).
- On the left side of the front of the board is the on LED which lights up when the board has power. It is labeled above the LED as on.
- Towards the right side of the back of the board is the LED jumper. It is two pads connected by a trace, labeled as LED to the left of the pads. If you'd rather not have the on LED lit up when the board has power, you can cut the trace between the two pads. To reenable the on LED, you can bridge the pads again with solder.