Lab 8: IQmath FIR Filter
8 - 38 C2000 Microcontroller Workshop - Numerical Concepts
11. Click the “Debug” button (green bug). The “CCS Debug Perspective” view should
open, the program will load automatically, and you should now be at the start of
main(). If the device has been power cycled since the last lab exercise, be sure to
configure the boot mode to EMU_BOOT_SARAM using the Scripts menu.
Run the Code – Filtered Waveform
12. Open a memory browser to view some of the contents of the filtered ADC results buffer.
The address label for the filtered ADC results buffer is AdcBufFilteredIQ in the “Data”
memory page. Set the format to 32-Bit Signed Integer. Right-click in the memory
window, select Configure… and set the Q-Value to 24 (which matches the IQ format
being used for this variable). Then click OK to save the setting. We will be running our
code in real-time mode, and will need to have the window continuously refresh.
Note: For the next step, check to be sure that the jumper wire connecting PWM1A (pin #
GPIO-00) to ADCINA0 (pin # ADC-A0) is in place on the Docking Station.
13. Run the code in real-time mode using the Script function: Scripts Realtime
Emulation Control Run_Realtime_with_Reset, and watch the memory
browser update. Verify that the ADC result buffer contains updated values.
14. Open and setup a dual-time graph to plot a 50-point window of the filtered and unfiltered
ADC results buffer. Click: Tools Graph Dual Time and set the following
values:
Acquisition Buffer Size 50
DSP Data Type 32-bit signed integer
Q Value 24
Sampling Rate (Hz) 50000
Start Address A AdcBufFilteredIQ
Start Address B AdcBufIQ
Display Data Size 50
Time Display Unit
µs
Select OK to save the graph options.
15. The graphical display should show the generated FIR filtered 2 kHz, 25% duty cycle
symmetric PWM waveform in the Dual Time A display and the unfiltered waveform
generated in the previous lab exercise in the Dual Time B display. Notice the shape and
phase differences between the waveform plots (the filtered curve has rounded edges, and
lags the unfiltered plot by several samples). The amplitudes of both plots should run
from 0 to 3.3.
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