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Revision: September 22, 2008

Note: This document applies to REV C of the board.

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Overview

The PmodJSTK was designed to be a versatile

user interface that can be used in a wide

variety of projects. It contains a resistive twin

axis joystick that includes a center push button

along with two additional push buttons. Also,

PmodJSTK has two programmable LEDs

located on the board that can provide

additional information to the user.

The PmodJSTK is ideally suited for Digilent

microcontroller or FPGA based projects that

required proportional control from the user,

such as robotic applications.

Functional Description

The joystick, located on the PmodJSTK,

contains two potentiometers which are

manipulated by moving the joystick in the X

and Y directions.

The PmodJSTK is equipped with an embedded

Atmel® ATtiny24 microcontroller in a MLF20

package. This microcontroller utilizes an

analog to digital converter to measure the

voltage occurring on the sweeper pins of each

of the two potentiometers. The voltage

occurring at these sweeper pins ranges from

ground potential to VCC depending on the

position of the joystick. A button is also

attached to the joystick and is activated by

pressing down directly on the joystick. The

joystick’s center button, along with the two

additional push buttons, is read by the

microcontroller.

The microcontroller assembles the joystick’s

positional data, along with the status of the

push buttons, in a series of five bytes. It

provides a 10-bit value for each axis of the

joystick. The joystick’s axis values are each

placed in 16-bit values, which are made up of

an upper byte and a lower byte.

Figure 1 PmodJSTK Circuit Diagram

Figure 2 Joystick Axis Map