Embedded Target for Texas Instruments C6000 DSPs

C6711 DSK Tutorial 2-3--Single Rate Application

In this tutorial you create and build a model that simulates audio reverberation applied to an input signal. Reverberation is similar to the echo effect you can hear when you shout across an open valley or canyon, or in a large empty room.

You can choose to create the Simulink model for this exercise from blocks in the DSP Blockset and Simulink block libraries, or you can find the model in the Embedded Target for TI C6000 DSP demos. For this example, we show the model as it appears in the demonstration program. The demonstration model name is c6711dskafxr.mdl as shown in the next figure. Open this model by typing c6711dskafxr at the MATLAB prompt.

To exercise this model you need a microphone connected to the Mic In connector on your C6711 DSK and speakers and an oscilloscope connected to the Line Out connector on your C6711 DSK. To test the model, speak into the microphone and listen to the output from the speakers. You can observe the output on the oscilloscope as well.

To download and run your model to your C6711 DSK, you complete five tasks:

1. Use Simulink blocks and blocks from other blocksets to create your model application.
2. Add the Embedded Target for TI C6000 DSP blocks that let your signal sources and output devices communicate with your C6711 DSK--the C6711 DSK ADC and C6711 DSK DAC blocks that you find in the Embedded Target for TI C6000 DSP C6711 DSK Board Support library.
3. Configure the simulation parameters for your model, including:
• Simulation parameters such as simulation start and stop time and solver options.
• Real-Time Workshop options such as target configuration and target compiler selection.
4. Build your model to the selected target.
5. Test your model running on the target by changing the input to the target and observing the output from the target.

Your target for this tutorial is your C6711 DSK installed on your PC. Be sure to configure and test your board as directed in Configuring Your C6711 DSK.

Building the Audio Reverberation Model

To build the model for audio reverberation, follow these steps:

1. Open Simulink.
2. Create a new model by selecting File -> New -> Model from the Simulink menu bar.
3. Use Simulink blocks to create the following model.

   

1. Look for the Integer Delay block in the Signal Operations library of DSP Blockset. You do not need to add the input and output signal lines at this time. When you add the C6711 DSK blocks in the next section, you add the input and output to the sum blocks.

4. Save your model with a suitable name before continuing.

Adding C6711 DSK Blocks to Your Model

So that you can send signals to your C6711 DSK and get signals back, TI C6000 includes a block library that contains five blocks designed to work with the codec and LEDs on your C6711 DSK:

• Input block (C6711 DSK ADC)
• Output block (C6711 DSK DAC)
• Light emitting diode block (C6711 DSK LED)
• DIP switch block (C6711 DIP Switch)
• Reset block (Reset C6711 DSK)

Type c6711dsklib at the MATLAB prompt to bring up this window showing the library contents.

Figure 2-9: Embedded Target for TI C6000 DSP Block Library c6711dsklib

These blocks are included in the Embedded Target for TI C6000 DSP c6000lib blockset in the Simulink Library browser.

The C6711 DSK ADC and C6711 DSK DAC blocks let you configure the codec on the C6711 DSK to accept input signals from the input connectors on the board, and send the model output to the output connector on the board. Essentially, the C6711 DSK ADC and C6711 DSK DAC blocks add driver software that controls the behavior of the codec for your model.

To add an input to the your model without using a C6711 DSK ADC block, add a DSP source block, such as a signal generator, that creates the discrete time signal you need and use that signal as the input to your model.

To add C6711 DSK target blocks to your model, follow these steps:

1. Double-click Embedded Target for TI C6000 DSP in the Simulink Library browser to display the C6000lib blockset.
2. Double-click DSK Blocks to view the C6711 DSK blocks.
3. Drag and drop C6711 DSK ADC and C6711 DSK DAC blocks to your model as shown in the figure.

   

4. Connect new signal lines as shown in the figure.

Configuring the Embedded Target for TI C6000 DSP Blocks

To configure the Embedded Target for TI C6000 DSP blocks in your model, follow these steps:

1. Click the C6711 DSK ADC block to select it.
2. Select Block Parameters from the Simulink Edit menu.
3. Set the following parameters for the block:
• Select the +20 dB mic gain boost check box
• For Output data type, select Double from the list
• Set Scaling to Normalize
• Set Source gain to 0.0
• Enter 64 for Samples per frame

1. Include a signal path running from the input to the output in your model so you can display both the input signal and the modified output signal on the oscilloscope for comparison.

4. For ADC source, select Mic In.
5. Click OK to close the Block Parameters: ADC dialog.
6. Now set the options for the C6711 DSK DAC block.
• Set Scaling to Normalize
• For DAC attenuation, enter 0.0
• Set Overflow mode to Saturate.
7. Click OK to close the dialog.

You have completed the model. Now configure the Real-Time Workshop simulation options to build and download your new model to your C6711 DSK.

Testing Your C6711 DSK

Configuring Simulation Parameters for Your Model