2 - RTDX – Real Time Data eXchange (Yahoo Chat)

Aim

To configure and use RTDX – Real Time Data eXchange (Yahoo Chat).

Theory

Compared to PC’s, Digital Signal Processors (DSP’s) are super-efficient when it comes to executing Signal Processing algorithms. Thus they are of immense use in the industry. But when it comes to the simple but essential task of display, the good old PC is miles ahead.

For example, you may run a complex algorithm and get a numerical result, ten times faster on the DSP than the PC. However, you cannot see the calculated value, as the DSP does not provide us any sort of Visual Display Unit (monitor, in simpler terms).

But wait! There is still hope. Texas Instruments DSP provides a mechanism called RTDX which can throw some light (literally!) on this problem. By this method, data is exchanged between the PC and DSP. A two way communication channel is set up. Using that, the result of any complex algorithm as calculated by the ‘super-fast’ but ‘visually disabled’ DSP can be sent to the ‘slow’ but ‘visually able’ PC. This experiment shows just how to do that.

Apparatus / Setup

Texas Instruments DSP – MATLAB & Simulink – Custom application for RTDX (e.g. – “General Purpose Display” provided by T.I.).

Procedure

1. Circuit

We make a simple circuit as shown below. The expected output is the constant 302, but we intend to generate it on the DSP and receive it on the PC screen. Set parameter ‘ochan1’ within the ‘To RTDX’ box.

2. Setup from MATLAB

Build the above circuit from MATLAB Simulink. (Note that you should choose the option ‘Build’ and NOT ‘Build & Run’ from the Simulation Parameters box. This can be accessed by the following steps.

After opening a new file in Simulink, go to the Simulation menu -> Simulation Parameters -> choose Real Time Workshop tab -> in Target Selection area, press Browse -> list of available tabs comes up, select Target for Texas Instruments TMS320C6000 Processor. The Build button should now show Build and Run. (Same procedure as Experiment 1).

Then, within the Category drop-down menu, choose “TI C6000 Runtime”-> then choose the Build Action : Build. The Build and Run button should again show Build.

3. Setup from CCS

During the Build process, Code Composer Studio (CCS) opens up. A new project is created and the executable for the above circuit is made. However it is still not loaded and remains on the PC awaiting further instructions.

RTDX has to be enabled next. This has to be done from CCS. Follow following steps to do so.

• From CCS, go to Tools Menu -> RTDX -> Configuration control
• Current Settings window opens up
• Uncheck the Enable RTDX checkbox
• Press the Configure button
• RTDX Configuration Control Window pops up
• Choose RTDX mode : continuous mode
• Press OK
• Check the Enable RTDX checkbox

This slideshow illustrates the above process. Zoom in and locate the mouse within these screenshots to view the changes.

Step 1	Step 2
Step 3	Step 4

After enabling RTDX, load the executable onto the DSP from CCS. From File menu -> choose Load Program. Do not execute it yet.

4. External Application Required

At this point, if you run the program on DSP, the value 302 will be generated on DSP and sent to the PC via parallel/ USB port. However we need an application to read the buffer where these sent values are stored. TI provides one such tool – General Purpose Display (GPD). (Search for this app within the folder where CCS is installed on your comp). Within GPD, Select Add Channel and provide the same channel name (ochan1). See Figures below.

Fig. General Purpose Display Program

Fig. Options for Adding Channel

Then run the executable on DSP. Just after that, press the Start button on GPD. You should see some familiar values popping up on screen.

Discussion

Provided everything ran successfully before, you can try other variations of the previous program.

For example, you may log the values of the DSP's digital clock using RTDX like in Fig. below.