Project:

The project goals are:

           Adjustable number of detents

           Adjustable foce threshold

           Software controlled damping

 

The team's design utilizes several components:

           Arduino Leonardo

           Firgelli L16-50-35-12-P actuators (2x)

           FSRs (4x)

           TI L293D H bridge

           MSU Eagle custom PCB print

The Arduino microcontroller is the heart of the team's project. This microcontroller allows for software control over the joystick. The Arduino has it's own IDE for programming which allows for USB plug-and-play, mouse movement, and keyboard libraries straight out of the box! It is perfect for the joystick since it has the required 7 digital pins and 6 analogue pins.

These actuators support the positioning the joystick. As the user pushes the joystick, the actuators will either lengthen or shorten, but what's special about these is that they have potentiometer position referencing.  This allows for equal positon based denting!

FSRs (Force Sensing Resistors) register force as pressure is placed on the pads. This value can be read through the analogue inputs of the Arduino.

The TI L293D allows the Arduino to drive the actuators in both forward and reverse directions. Using the h bridge is essential since the joystick will be able to talk quickly and reliably to the actuators. Here is the circuit schematic used to make this happen.

After creating the hardware prototyped in the video at top, the team used CadSoft EAGLE PCB design software and MSU fabricated the circuit. The PCB created can be used as a shield on top of the Arduino allowing the team to save space.

The code used for the controlling the Arduino is based off of standard libraries:

           USB plug-and-play

           Mouse HID

           Keyboard HID

 

Here is some pseudocode and a flowchart for the operation of the Arduino:

 

LOOP

WHILE serial input check for serial input serial input

IF valid serial input specified parameter to new serial value

ELSE exit serial input check

IF joystick position is equal to maximum or minimum position prevent movement

IF force threshold value is met or exceeded

INITIALIZE new position value

INCREMENT position counter

WRITE actuator movement


WRITE cursor movement

IF pedal click present perform selected click routine

END of loop body

 

 

 

These libraries allow for easy programming and out-of-the-box functionality. Connect the joystick to any computer runing any modern operating system (Window, Mac OS X, or Linux) and you are good to go!

And finally, to compliment the joystick here is an onscreen keyboard that is designed to work with and control the joystick. The keyboard also works independently as well. The keyboard has been written with Processing using the Processing IDE.

The Arduino IDE was developed off of the Processing IDE so both IDEs share some commonalities, such as serial communication. The team selected the Processing IDE for several reasons:

           Open-source environment

           Cross platform

           Solid serial communication with Arduino IDE

The keyboard supports a number of features:

           Visual based design

           Text-to-speech

           User defined dictionary

           Different sized layouts (4x4 to 12x12)

Processing IDE is designed with artists, hobbiest, and those new to programming. Being a visually based IDE not much

One such feature is text-to-speech. This feature uses an internet connection to retrieve and cache small .mp3 files for text-to-speach feedback. Frequently used words will remain cached so bandwidth can be preserved.

Here is a picture of dictionary words. Note, different size keyboards can be selected by choosing the red squares on either side of the keyboard: