Embedded Systems – Assignment 05
Making the Melody Roll-On
Introduction
You have now used three device drivers, the Ticker, the Real-Time Clock, and the Serial
Communication interface. It is time to jump in and do some internal design tasks. In this
project, you will complete the On-Off Sound device driver to make the sounds of the
melody program studied earlier.
Task 1
The OOSound.cpp device driver is based on the template consisting of (a) a hardware
ISR, (b) a software ISR, and (c) a data structure. Its basic operation should be something
like this –
1. The melody program wants to make a sound, corresponding to a musical note for a
certain time duration. It generates a call to the software ISR, passing the two arguments
of (a) the note’s frequency and (b) the time duration. The software ISR enqueues the two
pieces of information. Also, it checks to see if the hardware ISR is running. If it is not,
then it starts it. Thus, a queue is constructed consisting of all of the notes to be played.
2. The melody program can run a fast as allowed to enqueue all of the notes, and then it
will quit [a while( 1 ) loop].
3. Meanwhile, the hardware ISR is driven by a timer, being executed every n mSec. The
hardware ISR removes the information from the queue and causes a sound to be
generated on the speaker for the required amount of time. When it has run for the
specified time, then it removes the next note from the queue and does the same thing.
When the queue becomes empty, the hardware ISR shuts itself off by stopping the timer.
The driver, as presented in the text, is not complete. Several pieces of code have been
commented but not included. Complete the design of this driver, to make it work.
Carefully document all of your software and explain how it works.
Task 2
Make the melody program operate with your completed device driver. Demonstrate the
program’s execution. What happens if the queue is not big enough to hold the whole
melody? Show that your program works ok regardless of queue size.
Task 3
Carefully explain the organization of the whole system – the L0S and the L1S. Be sure to
discuss the content of the .h files associated with each.
Task 4
Modify the PlayMelody function and use the serial communication driver to show where
the melody is in execution, displaying the information (note, measure, phrase) with
hyperterminal. Carefully document and explain all that you must do to implement this
task.
