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Background Telemetry Channel (BTC) on the BlackFin

Background Telemetry Channel (BTC) on the BlackFin. Presented by Alan Martin Winter 2004 - ENCM 515. What is it?. BTC is a method of communication between an embedded processor (the Blackfin in this case) and the host (your computer).

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Background Telemetry Channel (BTC) on the BlackFin

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  1. Background Telemetry Channel (BTC) on the BlackFin Presented by Alan Martin Winter 2004 - ENCM 515

  2. What is it? • BTC is a method of communication between an embedded processor (the Blackfin in this case) and the host (your computer). • This communication occurs in the background, not interfering with other tasks that the processor may be performing at the time

  3. How does it work? • BTC uses shared registers that both the host and target application have read/write access to during program run-time • BTC is designed for use over a JTAG connection through an emulator • USB works, but to a limited extent

  4. Why do I care? • You can view data without having to stop the processor first. • You can view data that is constantly changing, and watch it change • You can change data values while the program is running, and the program will immediately use these new values without having to recompile

  5. WOW! How do I use it? • You need to include a library file with your project – libbtc532.dlb on the Blackfin 533 • You should also include btc.h with your project, unless you know all the macros you’ll need and define them yourself (this is a waste of time in my opinion, since the header file is easy to use)

  6. Is that it? • Not entirely. • You still need to define some BTC channels in your program • You also need to initialize BTC • Finally, you need to set the priority of BTC

  7. Channels? Like CNN? • You need to define a name for each channel (basically a label for some data you will read) • You also need to define the starting address and the length of the channel, much like a circular buffer

  8. Initialize? Priority? What? • BTC priority is determined by where you put the btc_poll function call. For example: • Placing it in a high-priority interrupt effectively makes it high priority • Placing it in a low-priority interrupt gives it low priority • Placing it in a loop in the main body of the function can have different effects depending on how interrupts on your system work

  9. Are you quite finished? • Well… no. • BTC is now setup and ready for use, but you have to setup the BTC window in VisualDSP++ to read/write the values. • You also need to do a couple things in order to view a plot being updated by BTC as you go.

  10. BTC memory? • The BTC memory window is a debug window, much like Plot. It can be accessed through the same menu • Double-click on a number to edit it (if possible).

  11. Plot windows with BTC? How? • Open a plot window as normal • Right click on the window and select Auto Refresh Settings… and then select the settings you need • Don’t forget to set the refresh rate and activate the Auto Refresh

  12. Now are you finished? • Yes. BTC is now ready to use! Build the program, run it, and you’ll see BTC in action!

  13. You lied! This doesn’t work! • The simulator does not currently support BTC • Using the USB connection will give you a much more limited amount of BTC. You can still view arrays, but only one plot at a time can be updated.(There may be other limits as well, but those are what I have found)

  14. Are there any examples? • There are a few sample programs available that use BTC. • Timer run using C code • Timer run using Assembly code • FFT code, which updates a plot • Audio example, where you can modify a value using BTC for volume control

  15. Did you say Assembly code? • Yes, I did. BTC can be run in Assembly code as well as C/C++. The code is only slightly more complicated.

  16. Now I can use BTC? • Now you can use BTC. • For best learning, download one of the examples and run it. The examples come with a readme.txt file that explains how to operate BTC in VisualDSP++. • There’s no better way to learn than by doing

  17. Who told you what to say?(aka References) • “VisualDSP++ Development Environment for Analog Devices Embedded Processors for Digital Signal Processing”, Analog Devices, 2003 • “VisualDSP++ Getting Started Guide for 16-bit Processors”, Analog Devices, n.d. • Examples programs of BTC operation from sample programs installed with VDSP 3.5

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