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Audioprocessor for Automobiles Using the TMS320C50 DSP

Audioprocessor for Automobiles Using the TMS320C50 DSP. Ted Subonj Presentation on SPRA302 CSE671 / Dr. S. Ganesan. Overview. Introduction Goals Hardware Components Software Components Conclusion. Introduction. Automobile Interior Space is Limited

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Audioprocessor for Automobiles Using the TMS320C50 DSP

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  1. Audioprocessor for Automobiles Using the TMS320C50 DSP Ted Subonj Presentation on SPRA302 CSE671 / Dr. S. Ganesan

  2. Overview • Introduction • Goals • Hardware Components • Software Components • Conclusion

  3. Introduction • Automobile Interior Space is Limited • Normal Echo is Not Present Inside an Automobile • Sound Inside a Car Can Lack a “Spacious” Quality

  4. Introduction • Audio Characteristics Which Determine Space Size, as Perceived By The Ear • Delay Between Original Signal and Echo • Difference in Volume Between Original Signal and Echo • Sound Coming From Different Directions • Ratio of Mono and Difference-Signal

  5. Goals • Goal Is To Create A New Sense Of Space (Independent Of Actual Room) • Four Signals Will Be Constructed From Two Stereo Channels • Output Signals Will Have A Variable Repetition Delay, Hence Simulating Echo • Output Signals Will Have A Variable Mono/Difference-Signal Mixing Ratio

  6. Hardware Components • Processor Unit • TMS320C50 DSP and Peripheral Components • Converter Unit • Crystal CS4225 AD/DA Converter • Analog Unit (Converter Unit Support) • Analog I/O Components • Filters for Internal Reference Voltages

  7. Hardware Components • I/O Interface • 74AC138 I/O Decoder with 2 x 8-bit Inputs, 2 x 8-bit Outputs • Memory Interface • 74AC138 Memory Decoder • 32kWord x 16-bit RAM Memory Space (Four 32k x 8-bit RAM Chips) • 32k x 8-bit EEPROM Code Space

  8. Hardware Components • UART-Serial Interface • Power Supply • Two 5V Regulators • Processor and Converter Serial Interface • Uses Both Processor Serial Ports for Communication • One Port for Audio Transmission in Both Directions • One Port for Communication With User Interface

  9. Hardware Components • LCD Display • Hitachi LMO93XMLN • 16 x 2 Character With Background LED Light • Keyboard • 6 Closing Keys Using 1 Input Port Each

  10. Software Components • Main Program • User Interface Runs in the Background • Read Keyboard • Write to LCD and Converter • Invoke the Active Menu Routine • User Interface CPU Utilization: 1%

  11. Software Components • Interrupts • Four Interrupt Sources • Receiving, Transmitting, and Processing of Data Performed in Interrupt Subprograms • Calculation of Mono Signal and Channel-Difference Signal • Mono Signal: Sum of Channels x Input Volume • Difference Signal: Channel Difference x Vol.

  12. Software Components • Echo Effects • Step 1: Take Value from Circ Buffer Using Echo Delay Pointer • Step 2: Multiply By Feedback Volume • Step 3: IIR Butterworth Low-Pass Filter • Step 4: Sum the Input and Feedback Signal and Restore it to the First Location of the Circular Buffer

  13. Software Components • Calculate Channel Signals • Get Mono and Channel-Difference Signals From Circular Buffer Using Repetition Pointer • Multiply By Their Respective Volume • Sum the Values and Write Them to the Channel’s Output Buffer

  14. Software Components • User Interface Adjustable Parameters • Main Volume (0 … 100%) • Attenuation for Converter’s Output • Mono Echo (0 … 100m) • Mono Signal’s Delay • Determines Difference Between Maximum Value and Repeat Value in Circular Buffer • Difference Signal Echo (0 … 100m) • Difference Signal’s Delay • Determines Difference Between Maximum Value and Repeat Value in Circular Buffer

  15. Software Components • User Interface Adjustable Parameters (Cont’d) • Mono Echo Feedback (0 … 100%) • Determines Volume of Echo’s Main Signal and Feedback • Difference Signal Echo Feedback (0 … 100%) • Determines Volume of Echo’s Main Signal and Feedback

  16. Conclusion • The Audioprocessor Was Based on a TMS320C50 DSP • The Audio Interface Used a Crystal CS4225 Audio Converter Module • The User Interface Hardware Consisted of a Hitachi LMO93XMLN LCD and 6 Keys • User Interface and Signal Processing SW Were Designed and Implemented

  17. Conclusion • Signal Processing Effects Were Developed and Tested Using the PC • Preprocessed Audio Data Was Played Using Two 16 Bit Sound Cards • The Hardware Was Built But Not Tested Due to PCB Delays

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