Arduino Touch Screen Keyboard

Top picture: the Arduino / Adafruit TFT touch screen ( http://www.adafruit.com/products/1651 ) assembly connected to a buzzer (top picture). (You could also connect your Arduino to a small 8 ohm speaker, but will need a 100 ohm resistor between the digital output pin and the speaker.)

Bottom picture: the Arduino / Adafruit TFT touch screen connected to a monobox amplified speaker (bottom picture - a Make Magazine project http://makezine.com/projects/make-34/monobox-powered-speaker-2/ ).

What we are going to do:

1. The Arduino sketch KeyboardOO demonstrates the use of the Adafruit touch screen shield as a 'piano' keyboard.
2. The 'OO' in the project title refers to Object Oriented. In KeyboardOO.ino normal Arduino style functions have been converted into object oriented program components.
If you have come to the Arduino with a background in object oriented programming, the attached sketch (keyboardOO.ino) will be sufficient explanation on its own.
But many of us, including the author of this Instructable, don't have the advantage of that programming knowledge. So the exercise of converting Arduino functions to classes and methods was at times mysterious and challenging. Luckily for me help was available, and I received substantial assistance. Thanks to Andrew Wendt for instructions and patience.

What we are going to use:

1. Arduino Uno
2. Adafruit 2.8" TFT touch screen shield for Arduino
3. A middle shield, made from a proto board that gives access to the Arduino pins that would have otherwise been covered by the TFT shield. The pictures showing the buzzer and monobox speaker show the bent-pin headers that give access to these pins. Step 2 gives further details.

The Adafruit TFT shield covers all of the input / output pins on the Arduino Uno. But some of these pins are not used by the TFT shield, so they are available for other Arduino functions, such as in this case to send signals to a buzzer or speaker.
These are the pins that are not used by the TFT shield: 2,3,5,6,7 digital; 0-5 analog, and 4 digital if the sketch does not use the SD card.
To gain access to the available pins, make an intermediate shield with a proto board and straight through female headers for those pins that are needed by the TFT shield. Use 90 degree female headers for the pins that are available for other purposes.

(Note: it's the TFT touch screen shield that covers the I/O pins. If you were to use the non-shield version of the TFT screen (see http://www.adafruit.com/products/1770 ) you would not need an intermediate shield - but the shield version is very convenient.)

Assembly
It's a bit tricky keeping all the pins straight when the two shields are assembled on the Arduino. Take care in aligning the shields.
Next install the piezo buzzer: plug one lead of the buzzer into Arduino pin A0 and the other lead into Arduino ground.

Loading the Arduino sketch.
Five files are required. keyboardOO.ino - the main sketch, two header files Key.h and Button.h, and two implementation files, Key.cpp and Button.cpp.
Load the main sketch into your Arduino IDE. Open a tab for each of the .h files (Button.h and Key.h) and .cpp files (Button.cpp and Key.cpp) and save these files in their respective tabs. The picture above shows how the main sketch, keyboardOO.ino, will look after these files have been saved.

Here are the files:

Run the sketch. The TFT keyboard will now perform as a touch screen mini keyboard.

Here is a demonstration video of how it looks and sounds:

Sketch has been converted to object oriented style

Why was this done?

My reason: because it's fun to learn things, and Arduino is all about learning.

The technical reason: because once you have converted your sketch into separate, object oriented components, it is easier to maintain - and these 'code components' are available to be put to other uses - for instance, you can use them in other sketches.
(Note: the usual term used for this object oriented component approach is 'encapsulation'.)

List of sketch features:
KeyboardOO has a number of features. (Study the sketch to see how these features were implemented.)
- It uses a TFT calibration routine for the touch screen. This routine is taken from the Adafruit example sketch 'On -- Off Switch'.
- It has touch-screen keys and buttons that allow you to play notes and change musical octaves. A full 7 octaves are available.
- It has a routine that monitors state changes - whether a key touch has changed since the previous reading. This is necessary to ensure a single touch, no matter the duration, only changes the octave once (i.e. it avoids jumping octaves).
- It sets an array of musical notes and their frequencies at the first octave. Musical frequencies increase by a factor of 2 to the power n where n is the selected octave number. (See http://en.wikipedia.org/wiki/Octave .) To make this frequency adjustment we have used the bitshift operator ">>" ( http://arduino.cc/en/Reference/Bitshift ). You could also use the power function "pow()" ( http://arduino.cc/en/Reference/Pow ) to achieve the same result.
- The keyboard keys and octave buttons have been converted to object oriented program components that draw the keys and buttons on the screen, and that check if a key or button has been touched.