1 / 34

Wireless Guitar Effects Processor

Wireless Guitar Effects Processor. ECE 345: Senior Design April 26, 2001. Group 26: Jeff Johnisee Ken Schutte Scott VanDyke. Objectives. Implement wireless transmission to increase mobility on stage and decrease number of cables in stage set-up

binta
Télécharger la présentation

Wireless Guitar Effects Processor

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Wireless Guitar Effects Processor ECE 345: Senior Design April 26, 2001 Group 26: Jeff Johnisee Ken Schutte Scott VanDyke

  2. Objectives • Implement wireless transmission to increase mobility on stage and decrease number of cables in stage set-up • Provide hands-free method to choose effect and modify its parameters • Construct simple modules to enclose circuitry and produce a marketable product

  3. System Overview TI 54x DSP A/D D/A serial Transmitter Reciever Amp HC12 A/D Guitar Amp ElectricGuitar Roland EV-5

  4. Initial DSP Plan • Reverberation • Using Comb and All-Pass Filters • Phasing • Using 4 Oscillating All-Pass filters • 4-tap Delay • Using 5 Delay Buffers

  5. DSP Implementation • Reverberation • 4 All-Pass Filters in Series • Phasing • Using 1 Oscillating All-Pass filters • 4-tap Delay • No Change

  6. Block Diagram of All Pass Filter Frequency Response Input g Z-N g Output

  7. Block Diagram of Phaser 1-mix Input output All Pass mix LFO

  8. Phaser Specifications • All Pass Delay (varying) • 1 – 255 Samples (0 - .0059 Seconds) • Phase Length (user varying) • 0.75 – 16.2 Seconds • All Pass Gain • 0.625

  9. Impulse Response

  10. Block Diagram of 4-Tap Delay

  11. 4-Tap Delay Specifications • Delay Line Lengths (real time user varying) • 0 - 65535 Samples (0 – 1.5 Seconds) • 0 - 32768 Samples (0 - .75 Seconds) • 0 - 16384 Samples (0 - .375 Seconds) • 0 - 8192 Samples (0 - .186 Seconds) • Delay Taps • 0.75 • 0.6 • 0.5 • 0.4 • Decay (real time user varying) • 0.5

  12. Impulse Response

  13. Block Diagram of Reverb 1-mix Input output AP AP AP AP mix decay

  14. Reverb Specifications • Delay Line Lengths • 840 Samples (.02 Seconds) • 636 Samples (.015 Seconds) • 2248 Samples (.05 Seconds) • 1644 Samples (.04 Seconds) • All Pass Gain (real time user varying) • ~0 - 0.625 (AP1, AP2) • ~0 - 0.750 (AP3, AP4) • Decay (real time user varying) • ~0 - 0.50 • Mix • 0.50

  15. Impulse Response

  16. Signal Amplification • Electric guitar output • full volume  200-300mV • peaked around 500mV • constant 35-40mV noise

  17. Amplifier Circuit: basic audio pre-amp

  18. Amplifier Frequency ResponseVout p-p vs. input frequency for 100mV p-p sine wave

  19. Initial design: Build simple AM transmitter / receiver Adjust sensitivity to fit guitar audio spectrum Simplicity would make troubleshooting easier Final design: LINX analog RF chips ¼ wave whip antennas Separate containers if time permits WIRELESS DESIGN

  20. FM mod / demod for analog signals. 8-channel binary selective operating freq. In 902-920 MHZ band. 2.7-16V DC supply voltage range. Module design includes VCO(oscillator) only requires antenna and power. Designed for high-quality wireless audio. Covers 50HZ – 25kHZ audio band. Relatively low cost, pair around $60. LINX HP-II 900MHZ TRANSMITTER / RECEIVER PAIR

  21. FM MODULATION • LPF shapes signal to 25kHz BW • VCXO serves as freq. reference and is directly mod. • PLLlocks on to phase and sets Tx freq. According to chan. sel. Lines. • Microcontroller sets CTS high.

  22. FM DEMODULATION • SAW BPR for unwanted RF energy not in BW. • LNA increases receiver sensitivity and lowers noise. • IF receiver strip converts the signal to 2 IF levels and performs the demodulation. • Active LPF cleans up audio signal. • RSSI is set high when signal strength is good.

  23. WIRELESS SYSTEM LAYOUT

  24. Signal strength (dBm) in red. Noise strength (dBm) in blue. SNR = 9.875. Noise floor evident in transmitted audio. SNR OF Tx / Rx PAIR

  25. OVERALL PERFORMANCE OF WIRELESS SYSTEM • Considering: • Small percentage of wireless project success • Small signal strength and BW of guitar signal • Very satisfied with audio quality! • Noise heard from amp could also be attributed to: • Guitar grounding problem • Poor jack connection on amp

  26. HC12 Microcontroller • Interface between user controls and DSP • Monitors selection buttons • Reads controller pedal through A/D • Activates status LEDs

  27. Roland EV-5 controller pedal • Acts as variable voltage source • Pedal sweeps between Vmin and Vcc • Side knob controls Vmin • Sent to A/D and represented by 8 bit value

  28. Serial Communication • One byte specifies effect and control level A5 A4 A3 A2 A1 A0 S1 S0

  29. Serial Set-up: The HC12 SCI • Baud Rate Control Register • SCI Baud Rate = MCLK/(16*SBR) • 8MHz clk, 9600 bps  SBR = 0x34 • SCI Control Registers • Enable transmitter, reciever SC0CR2 = 0x0C • One stop bit, eight data, no parity  SC0CR1 = 0x00

  30. Serial Set-up: TI EVM320C549 • TL16C550 Serial Controller • Configured in core.asm code • Accessible Registers • LCR = 0x03 : 8 data bits, 1 stop bit, no parity • Baud Rate Generator: divisor for 3.6864MHz • 3686400/N = 16*(9600 bps)  N = 24 • MCR = 0x01 : Data terminal ready

  31. Problems and Obstacles • Wireless design • RF interference • Signal strength • HC12 • Chip problems • Serial interface • DSP • Reducing noise • Output quality

  32. Audio quality of effects Wireless audio HC12 control Production of finalized product Successes

  33. If we had more time… • Integration of DSP and controller boxes • Manufacture printed circuit board • Development of more elegant and user-friendly power supplies

  34. Questions?

More Related