Lab 7: Event Manager
Start Address AdcBuf
Acquisition Buffer Size 50
Display Data Size 50
DSP Data Type 16-bit unsigned integer
Sampling Rate (Hz) 50000
Time Display Unit
µs
Select OK to save the graph options.
10. The graphical display should show the generated 2 kHz, 25% duty cycle symmetric
PWM waveform. The period of a 2 kHz signal is 500 µs. You can confirm this by
measuring the period of the waveform using the graph (you may want to enlarge the
graph window using the mouse). The measurement is best done with the mouse. The
lower left-hand corner of the graph window will display the X and Y-axis values.
Subtract the X-axis values taken over a complete waveform period (you can use the PC
calculator program found in Microsoft Windows to do this).
Frequency Domain Graphing Feature of Code Composer Studio
11. Code Composer Studio also has the ability to make frequency domain plots. It does this
by using the PC to perform a Fast Fourier Transform (FFT) of the DSP data. Let's make
a frequency domain plot of the contents in the ADC results buffer (i.e. the PWM
waveform).
Click:
View Graph Time/Frequency… and set the following values:
Display Type FFT Magnitude
Start Address AdcBuf
Acquisition Buffer Size 50
FFT Framesize 50
DSP Data Type 16-bit unsigned integer
Sampling Rate (Hz) 50000
Select OK to save the graph options.
12. On the plot window, left-click the mouse to move the vertical marker line and observe the
frequencies of the different magnitude peaks. Do the peaks occur at the expected
frequencies?
7 - 38 C28x - Event Manager
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