The Arcade QT is full of fun features. Here's a detailed look!

Switch Connectors

Spread out along the board are four two-pin JST XH switch connectors. They are labeled as SWITCH1, SW #2, SW #3, and SWITCH4. Using the JST XH quick connect cables, you can easily connect four arcade button switches to this board. The switches are on the following pins on the board's seesaw microcontroller:

  • SWITCH1 is on pin 18.
  • SW #2 is on pin 19.
  • SW #3 is is on pin 20.
  • SWITCH4 is on pin 2.

LED Connectors

Spread out along the board, opposite the switch connectors, are four two-pin JST XH LED connectors. They are labeled as LED1, LED2, LED3, and LED4. Using the JST XH quick connect cables, you can easily connect four arcade button LEDs to this board. The LED connectors are on the following pins on the board's seesaw microcontroller:

  • LED1 is on pin 12.
  • LED2 is on pin 13.
  • LED3 is is on pin 0.
  • LED4 is on pin 1.

STEMMA QT Connectors

On the bottom of the board, near each end, are two STEMMA QT connectors. These allow you to connect to development boards with STEMMA QT connectors or to other breakouts using various associated accessories.

ATTiny817 seesaw Microcontroller

The Arcade QT breakout uses an ATtiny817 microcontroller to take I2C commands and converts them to digital or PWM signals.

Address Jumpers

In the center of the back of the board are four address jumpers. These jumpers allow you to chain up to 16 of these boards on the same pair of I2C clock and data pins. To do so, you cut the traces between the the two pads.

The default I2C address is 0x3A. The other address options can be calculated by “adding” the A0/A1/A2/A3 to the base of 0x3A.

A0 sets the lowest bit with a value of 1, A1 sets the next bit with a value of 2, A2 sets the next bit with a value of 4, and A3 sets the high bit with a value of 8. The final address is 0x3A + A3 + A2 + A1 + A0 which would be 0x49.

  • 
If only A0 is cut, the address is 0x3A + 1 = 0x3B
  • 
If only A1 is cut, the address is 0x3A + 2 = 0x3C
  • 
If only A2 is cut, the address is 0x3A + 4 = 0x3E
  • If only A3 is cut, the address is 0x3A + 8 = 0x42


So for example if A2 is cut and A0 is cut, the address is 0x3A + 4 + 1 = 0x3F.

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

Through-Hole Pads

In the center of the board, on each edge, are a set of six through-hole pads for use with header pins and a solderless breadboard. They are labeled on the top and the bottom of the board for easy identification.

When viewed from the of the top of the board:

  • VIN - This is the power pin. Since the chip can use 3 or 5 VDC. 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.
  • GND - This is the ground pin. It is the common ground for power and logic.
  • SCL - This is the I2C clock pin. Connect to your microcontroller I2C clock line. This pin can use 3-5V logic, and there's a 10K pullup on this pin to VIN.
  • SDA - This is the I2C data pin. Connect to your microcontroller I2C data line. This pin can use 3-5V logic, and there's a 10K pullup on this pin to VIN.
  • INT - This is the interrupt pin. The Seesaw allows for setting GPIO interrupts. This pin will go low when a button is pressed.
  • UPDI - This is the single-pin Unified Program and Debug Interface for the ATtiny817. This pin is for external programming or on-chip-debugging.
If you're going to use a solderless breadboard with the Arcade QT breakout, you should solder headers to both sides of the breakout for stability.

Power LED and Jumper

In the lower left corner, on the back of the board, is the power LED, labeled on. To the left of the LED is the power LED jumper pad, which defaults to closed. Cut the trace to disable the power LED. Once cut, you can solder it closed again to enable the LED.

This guide was first published on Feb 02, 2022. It was last updated on 2022-02-04 11:51:33 -0500.

This page (Pinouts) was last updated on May 24, 2022.

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