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EE 478 Final Project

EE 478 Final Project. 49-key MIDI keyboard. Jonathan Feucht, Whitney James. Introduction. 49-key touch insensitive keyboard Utilizes the ATSAM2195 Low-power Single Chip Synthesizer with Effects Adjustable settings using an LCD 16×2 character Crystalfontz CFA-533 display. Introduction.

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EE 478 Final Project

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  1. EE 478 Final Project 49-key MIDI keyboard Jonathan Feucht, Whitney James

  2. Introduction • 49-key touch insensitive keyboard • Utilizes the ATSAM2195 Low-power Single Chip Synthesizer with Effects • Adjustable settings using an LCD 16×2 character Crystalfontz CFA-533 display

  3. Introduction Topics covered in this presentation: • Project description • Design specification • Hardware / Software implementation • Design procedure • Challenges encountered • Design improvement ideas

  4. Design requirements • Low key latency (< 800 µs) • USB or battery powered (< 2.5 Watts total) • Adjustable volume, reverb, chorus levels • Adjustable reverb / chorus types • Pitch-bend mode • Transposition • Selection of 100+ instrument sounds • 3.3 V 150 mA supply for keyboard controller / Atmel synthesizer chip • 5 V supply for LCD screen, audio amp, and speakers.

  5. Design requirements • Communication protocols • Parallel communication with ATSAM2195 chip • I²C communication between Keyboard controller and LCD driver • LCD menu master • Keyboard controller slave • RS-232 communication with LCD screen

  6. Hardware implementation

  7. Hardware implementation • Crystalfontz CFA-533 LCD • 16×2 character • Uses 19200 RS-232 • 6 navigation buttons

  8. Hardware implementation • User front end - Seeeduino • 16 MHz ATMEGA328P • Controls LCD display • EEPROM used for saving settings after powerdown • I2C Master

  9. Hardware implementation • ATSAM2195 Atmel synthesizer chip • QFN-44 package with ground plane • Measures 0.7×0.7×0.2 cm3

  10. Hardware implementation • Operates 3.3 V supply • 2.2 Vpp analog output signal • Configured in parallel implementation

  11. Hardware implementation • Amplifier stage for driving on-board speakers:

  12. Software implementation • Crystalfontz CFA533 driver • Data sent out and received in “packets” • Command • Data length • Data • CRC checksum • For every command sent out, return packet is sent back

  13. Software implementation • Buttons used for navigating tree-style menu • Left: Follow to parent menu • Right: Follow to child menu • Up: Navigate up the menu list • Down: Navigate down the menu list • Okay: If selectable, execute command or select setting; otherwise, navigate to child menu • Cancel: Go to main menu

  14. Software implementation • Button polling • Command is issued to display to return states of buttons • Return packet is 3 bytes, indicating: • Buttons pressed down since last poll • Buttons released since last poll • Buttons currently being held down • Data ended up being NOISY • Filtered data by debouncing keys • Adjusted for smooth menu navigation

  15. Software implementation

  16. Software implementation • Tree menu • Implemented as tree of menu nodes • Used for modifying all keyboard settings • Each menu node consists of a complex data structure • Each node has pointers to parent node, and an array of pointers to children nodes

  17. Menu node data structure:

  18. Software implementation

  19. Software implementation • I2C Arduino / Pic communication • Synchronization on boot-up • Arduino sends settings to PIC using 2 bytes of data • After sending setting, Pic sends acknowledge code back

  20. Design procedure

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  38. Results

  39. Results • Measurements • Key polling: Max 250 µs • I2C setting transfer: 179 ms • Power consumption: 1.2 Watts • Keyboard controller / synth chip: 0.216 Watts • Speakers / audio amplifier: 0.200 Watts • LCD display: 0.505 Watts • Seeeduino board: 0.279 Watts

  40. Challenges encountered • Reflow soldering for QFN-44 package • Procedure • Testing • 3.3 V vs. 5 V • Using program memory for menu drivers • ATSAM2195 initialization • LCD driver communication • Frustrations with Arduino environment • No μs delays • Arduino environment I²C drivers would not trigger interrupts on the PIC during reads

  41. Project status • Working as is • Planning to add more features; perhaps include second instrument package, enable drum patch, or something else.

  42. Ideas for improvement • More keys!!! • More features • Free up pins on the keyboard controller • Touch-sensitive key action • Incorporate everything on only one microcontroller

  43. Conclusion • We successfully implemented a prototype for a keyboard instrument for midgets • Still has room for more features and creativity • Our project is way cooler than Torin, Daniel, and Russell’s project

  44. DEMO

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