Question

I have a class on low-level programming which requires a final project (syllabus at the end). It is basically a piece of software that puts to use all you learned.

I had a few ideas, like designing my own Roguelike (should be kind of like NetHack, only single-player), but I’d like some suggestions on alternatives. It needn’t be a game; it can be anything. The time frame is a month and a half, and I have other projects, etc. so it shouldn’t be too time-consuming to implement.

Requirements:

• Use, at least, four I/O devices, one of which should be the mouse or serial port
• Some of those devices should use interrupts, others should use polling
• Languages: C and Assembly (mandatorily, else there is a penalization)
• Implement state machines

The peripherals we were lectured on were:

• Graphics card – Graphical mode
• Graphics card – Text mode
• Mouse
• Keyboard
• Real Time Counter
• On-board Speaker (via timers 0 and 2)
• Serial port

This is the abridged syllabus:

Input/Output peripherals and their
operation Direct mapping in a process
address space Access to peripherals in
polled mode and by interrupt Processor
interrupts in the IA-32 architecture
and the interrupt controller. Writing
interrupt service routines in Assembly
and in C Study of some typical
personal computer peripherals, such as
keyboard, mouse, graphics card, real
time clock, timer, loudspeaker and
serial port.

Programming in the C programming
language: main differences with
respect to C++ language; structured
programming in C. Memory layout of a
process. Function calls: mechanisms,
parameter passing, storage of local
variables and return values. Combined
programming in C and the IA-32
processor family assembly. Creation
and use of libraries. Static linking
of object code.

Use of software development tools:
gcc, make, gdb, ar, prof, diff, patch
and SVN

Answer 1

One simple option is to go for games. They can always use several devices, such as mouse, keyboard, timers, graphics card and (depending what you do) the RTC.

Another option is to go for a "music composer" application. For instance, you could write (using the keyboard and mouse) a song (note frequency, duration) and then let the computer speaker play it.

You could also go for a "clock/calendar application". It could draw a clock in the screen (which might be harder than it might look if you draw an analog one on the screen), and then let the user adjust the time of the day(saving the changes in the RTC). The clock could also include alarm and some ticking sound.

As for the calendar, you could also allow the user to create "events" in the calendar, which could work a bit like alarms.

You could also try to write your own "notepad"-like application. This would require having a working GUI(write area, menus, etc.). This could either be in text or graphics mode. You could detect the keyboard being pressed to add character, handle CAPS LOCK (giving you the opportunity to mess up with the keyboard LEDs). You could use mouse position/clicks to change position in text editor or trigger menus. Then timers to have the blinking caret in the text editor. Clicking a disabled menu option could cause a short speaker sound to indicate an invalid action.

I’d recommend writing most of the code in C, except for little bits in Assembly. ISRs are a good opportunity for Assembly code.

Regarding state machines:

1. Games can have many states ("Main Menu", "Playing Game", "Pause Menu", "High scores") with well defined transitions between states.
2. A music composer could have some states too("Stop", "Pause", "Playing")
3. A clock application could have states such as "Show Clock", "Show Calendar", "Alarm Message Box", "Event Message Box", "Event Message Box With Pending Alarm.
4. The notepad application could have states such as "Editing Text", "In Menu" or "In Message Box")

Most of the devices you mentioned can be accessed with interrupts. Unfortunately, I can not think of good opportunities for polling…