Calculating resonant frequency in series RC oscillator

[opticaltempest]

What is the formula to calculate the oscillating (resonant?) frequency of a series RC circuit with a constant DC voltage?

For example the RC circuit shown at this site:

http://www.mikroelektronika.co.yu/english/product/books/PICbook/2_02chapter.htm"


How does this circuit resonate with a DC voltage? Aren't capacitors supposed to act like an open circuit to DC voltage?

I have searched all over using google but cannot find details on RC oscillators.

 

[Averagesupernova]

There is more going on inside the microcontroller than you are able to see. The RC circuit sets up a time constant. When the voltage is first applied to the circuit there is a specific amount of time it takes before the voltage at the node of the capacitor and resistor reaches a specific level.
.
Think of it this way: The microcontroller senses this voltage and modifies the circuit to discharge the capacitor at a specific rate. Then it senses a lower limit and allows the capacitor to charge again.

 

[Link_pad]

I'm no expert but it sounds like the 555 timer chip. This chip uses capacitors and resistors as a reference time constant, then from this creates a pulse signal. By the way the output of the 555 timer is not strictly A/C sinsoidal but sawtooth.So almost like using a rapid on/off switch with C & R setting the speed.