COSC 4290 Embedded Systems

Spring 2014

Homework Assignment #3

"And when the music stops, the rest is silence..."
--Merrick, Buffy The Vampire Slayer

Due: Wednesday, February 12th, 11:00am CST
Submit: Turn your C source file using the turnin command on the Systems Lab machines.
Expect to present a demonstration of your system during lab time.
Work is to be completed individually.

Pulse Width Modulation

Plug your mbed into the mbed application board, being careful to correctly align the pins on the inner headers with proper orientation.

Following the examples given in the textbook and on the website, construct a program that reads analog values from the two potentiometers, (analog inputs on pins 19 and 20,) and uses those values to alter the colors of the RGB LED, (PWM outputs on pins 23 [red], 24 [green] and 25 [blue].)

Music

When the joystick center button is pushed (digital input on pin 15,) your mbed should play a tune on the speaker (PWM output on pin 26.) Example frequency tables and song data are included at the end of chapter 4.

Optional Enhancements

Once you have the required functionality in place, here are some possible extensions you could consider:

• Use the other dimensions of the joystick inputs to alter the third LED color.
• Rather than the obvious correspondence between the analog potentiometer inputs and two of the LED output, devise a more complex mapping that allows two potentiometers to explore a different region of the three-dimensional LED color space.
• Use serial input from the host keyboard (see the PC serial port examples in the book) to trigger different notes on the speaker. With some practice, one could play a song on the mbed with keyboard inputs. (Use minicom -S /dev/ttyACM0 -b 9600 on the Linux host to connect to the mbed serial port.)