Blackberry Trackball

An alternative to a Rotary Encoder is the Blackberry Trackball. These breakout boards can be found relatively cheaply on Amazon, eBay, Alibaba, etc.

They have the following features:

UP, DOWN, LEFT, RIGHT hall-effect sensors for navigation.
BLUE, RED, GREEN and WHITE surface mount LEDs (via 180 ohm resistors) behind trackball.
- Note: The BLUE and RED LEDs on these boards seem to be swapped!
Push to make dome switch (Pulled up VCC by 10K ohm resistor, push to make to GND).

Connecting to Gotek

You can choose to either connect the DOWN/UP or LEFT/RIGHT (or join DOWN/LEFT and UP/RIGHT for both) to the Gotek.

Connect the pins to the J7 Pins 1 and 2:

Connect the BTN pin of the Trackball board to the JA pin on the Gotek.

The Trackball LED pins are the Anode side of the LED:

You can make the trackball light up different colours depending on which of the four LEDs are supplied VCC voltage.

On the Gotek there are typically two LED lights:

The Cathode side of these LEDs are connected to the Gotek MCU on pins (FPI5V_DSELn and DISP_DIO) that are pulled up to VCC, and are active low.

This means that inverter circuit is required if you want to drive the LEDs on the Trackball board correctly.

A suggested setup would be:

(Note: The BLUE and RED LEDs on these boards seem to be swapped!)

Without an inverter circuit connected the Activity light you will have the following behaviour:

With an inverter circuit connected the Activity light you will have the following behaviour:

An example of how an inverter circuit works in this setup can be seen below - click on the L/H switch to simulate the signal:

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