PIC32MX: Sinusoidal Analog Output

Overview:

How do we obtain analog output? ie PWM (brief description)

How do we get sinusoidal output? ie divide up sinusoid into N points, scale duty cycle accordingly

General discussion about how cutoff frequency, number of points period (N) and the RC time constant matter.

State that the examples here have PWM at 20kHz.

Cutoff Frequency

How to choose cut-off frequency -- what is the equation?

Show picture if you choose your frequency to high and if you choose your frequency to low.

Say something about how the amplitude decreases with high frequency

Number of Points Per Period

Show Pictures of number of points to small - discuss that you see the capacitor charging

Show picture of good number of points

RC Time Constant

The RC time constant plays a big role in creating the sine wave. By increasing the RC constant, the quality of the output signal is increased, where "quality" refers to the width of the output signals. Despite having such advantages, a larger RC constant will result in a phase lag which causes a delay between the output of the PIC and the output from the whole circuit.

The sine waves were generated at 25Hz with 100 points. The sine wave labeled 1 was generated with an RC constant of 4.7 x 10^-5, the sine wave labeled 2 was generated using an RC constant 2.2 x 10^-4 and the sine wave labeled 5 was generated using an RC constant 4.7 x 10^-3.

Sample Code

Include your sample code (this may need cleaned up a bit).

To make a box around the code, put a 'space' in front of each line.