Re: PC Based oscilloscope
Measuring in the voltage domain is quite easy although achieving 1MHz bandwidth without using special hardware could be a problem. The internal ADC in a PIC isn't fast enough to sample at 2MHz (the absolute minimum rate to see 1MHz signals).
If you convert to frequency, the measurement becomes far more difficult. To be able to measure a frequency which is modulated at 1MHz, it has to be at least (Nyquist limit) 2MHz at it's lowest and a PIC will struggle to measure such short cycles accurately. If you increase the frequency to improve resolution, you decrease the ability to measure it accurately. Even if you could measure it, at such high frequency deviation it would be very difficult to keep the frequency increase linear to the voltage.
You might be able to sample fast enough if you use two or more PICs with the ADC triggering alternating between them but keeping them in sync would be difficult.
Brian.