The default I2C address is 0x49.

Power Pins

• VIN - This is the power pin. To power the board, give it the same power as the logic level of your microcontroller - e.g. for a 3V microcontroller like a Feather RP2040, use 3V, or for a 5V microcontroller like Arduino, use 5V. There is a 5V boost converter onboard to supply an attached PC joystick with 5V.
• GND - This is common ground for power and logic.

I2C Logic Pins

The default I2C address is 0x49.

• SCL - I2C clock pin, connect to your microcontroller I2C clock line. There's a 10K pullup on this pin.
• SDA - I2C data pin, connect to your microcontroller I2C data line. There's a 10K pullup on this pin.
• STEMMA QT - These connectors allow you to connect to development boards with STEMMA QT / Qwiic connectors or to other things with various associated accessories.

Interrupt Pin and LED

• IRQ - This is the interrupt output pin. It can be configured to pulse low whenever an input from an attached PC joystick is detected so you do not have to spam-read the I2C port to detect input.
• Interrupt LED - On the front of the board, directly above the IRQ pin, is the interrupt LED. It is the red LED and turns on whenever an interrupt is detected.

UPDI Pin

• UPDI - This is the single-pin Unified Program and Debug Interface. This pin is for external programming or on-chip-debugging for the ATtiny816 running the seesaw firmware. We have a page in the ATtiny Breakouts with seesaw Learn Guide detailing how to reprogram these chips with your own firmware (at your own risk). We don't provide any support for custom builds of seesaw - we think this is cool and useful for the Maker community.

5V LED

• 5V - On the front of the board, next to the IRQ LED, is the 5V LED, labeled 5V. It is the green LED. It acts as a power indicator LED that receives power from the 5V boost converter. 

DE-15 Port

The large, chonky port on the adapter board is a 15 pin D-Sub socket port. Your vintage analog PC joystick will plug into this port, just like how you used to plug into your Game Port on your PC add-on card. You'll be able to read the joystick X & Y plus button inputs.

If you're curious what these analog joysticks look like inside, check out the teardown that Ladyada did with the Gravis Advanced Classic PC Joystick in the video below.