Crystals are actually more expensive than comparable oscillators.

Alps has some but they tend to be quite expensive.

A cheaper solution would be to use a rotary switch to control a digital pot.

why would I do that when I have the ISR? Besides, eventually I want to sleep the chip and have the ISR wake it every second (or five seconds). Not sure if that's going to happen, but it's the goal.

Advance a counter / time struct in the isr.

To wake it up, you need to have an isr on the LF oscillator.

if you dismantle the USPS it will just be replaced by other services (FedEx, UPS, etc.) at a higher cost.

Cost is just one of many factors evaluated for delivery service. I for one don't mind paying more, if usps can provide certainty of service.

I guess that's why I don't use usps.

BarBot

BarBot!

Just what you need at the SuperBowl party.

what exactly is wrong with a goto?

It doesn't provide inferior people the ability to feel otherwise.

There are many ways to do it, from the simplest of directly adc'ng the ac signal, to ieee-1057 7-parameter estimation / dft.

You will need to figure out their pros  / cons.

At OCR = 0, you get 16khz;
OCR = 1, you get 8khz;
OCR = 31, you get 0.5khz.
...

19 system clock cycles, yes?

No. The latency varies, depending on many factors, starting from as low as 2.

Why did you recommend a series resistor to the gate

So during high speed switching, the mosfet can burn up faster / sooner.

expecting the Atmel code to work perfectly.

It will work perfectly, on its intended target.

All you need to do is to understand what the code is doing, read the datasheet of your own target and replicate the same on your target: aka what an application note is designed to do.

It shouldn't be so hard

Nothing is difficult, until you start doing it.

Use the capture function.

I'm thinking it might not be an option there.

What made you think so?

I remember something about potatoes being used as batteries

There are examples of using potato / tomato / apple / etc. to power your mcu.