Do I need a RTOS?

I am bringing up my first ARM project (based on LM3S1439) and am looking
for some advice. In my particular target application the processor will be
communicating with several peripherals via SPI (2) and UART, maintaining a
file system, keeping track of time and date as well as performing a lot of
GPIO manipulation. The board is also designed with a few external
communications ports so that future additions can be accommodated.

I can see lots of wait states in the manipulation of the GPIO. For example
I might have a function that sets a pin, waits for 500ms, then clears a
pin. I could probably get away with software delays at this moment but,
given the fact that the design can scale, I don't want to introduce this
inefficiency now only to have to remove it a few months down the road. That
500ms could be precious later on. I have several timers at my disposal but
I can foresee 'running out' in the future. I can think of some elaborate
solutions to this problem but it makes for messy code.

In general I was thinking I could implement a system tick which generated
an interrupt at a known interval (say 1ms). Upon each tick, I could examine
counters associated with the periodic tasks to see if they are due for
execution. The random interrupts would be handled by the specific interrupt
handler for that peripheral (example UART receive). That seems straight
forward to me. However, how best handle (cleanly) the toggling of a pin
after a certain delay? It's not a periodic task.

Should I use a full blown RTOS? If not how should I structure my
application? I've had a look at FreeRTOS but it looks to be much more than
I need and slightly intimidating.

Any suggestions? Please feel free to speak to me like a child as I am not
extremely knowledgeable of operating systems or software architecture(I am
a EE). Also, if you can point me to or provide examples that would be
extremely helpful! Help me wrap my brain around this problem.

Thanks!


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