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 Topics covered in this presentation:  Project description   Design specification Hardware / Software implementation    Design procedure Challenges encountered Design improvement ideas

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.

Design requirements 

Communication protocols

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Parallel communication with ATSAM2195 chip I²C communication between Keyboard controller and LCD driver

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LCD menu master Keyboard controller slave

RS-232 communication with LCD screen

Hardware implementation 7 Column selector 8 Row data Keyboard controller PIC18LF4525 (I ²C Slave) 49 Keys, organized as button matrix with 7 columns, 8 rows Pitch Bend Optoelectronic Device 2Y0A21 I ²C User Interface ATMEGA328 (I ²C Master) RS232 LCD / Keypad Module CFA-533 8 Parallel MIDI Synthesizer ATSAM2195 Audio Amplifier Speaker

Hardware implementation  Crystalfontz CFA-533 LCD  16 ×2 character  Uses 19200 RS-232  6 navigation buttons

Hardware implementation  User front end - Seeeduino     16 MHz ATMEGA328P Controls LCD display EEPROM used for saving settings after powerdown I 2 C Master

Hardware implementation   ATSAM2195 Atmel synthesizer chip QFN-44 package with ground plane  Measures 0.7

×0.7×0.2 cm 3

Hardware implementation    Operates 3.3 V supply 2.2 Vpp analog output signal Configured in parallel implementation

Hardware implementation  Amplifier stage for driving on-board speakers:

Software implementation 

Crystalfontz CFA533 driver

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Data sent out and received in “packets”

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Command Data length

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Data CRC checksum For every command sent out, return packet is sent back

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

Software implementation 

Button polling

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Command is issued to display to return states of buttons Return packet is 3 bytes, indicating:

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Buttons pressed down since last poll Buttons released since last poll Buttons currently being held down Data ended up being NOISY

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Filtered data by debouncing keys Adjusted for smooth menu navigation

Software implementation

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

Menu node data structure:

Software implementation

Software implementation  I 2 C 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

Design procedure

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Results

Results  Measurements  Key polling: Max 250 µs  I 2 C 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

Challenges encountered      

Reflow soldering for QFN-44 package

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Procedure Testing

3.3 V vs. 5 V Using program memory for menu drivers ATSAM2195 initialization LCD driver communication Frustrations with Arduino environment

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No μs delays Arduino environment I²C drivers would not trigger interrupts on the PIC during reads

Project status  

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

Ideas for improvement

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More keys!!!

More features Free up pins on the keyboard controller Touch-sensitive key action Incorporate everything on only one microcontroller

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

DEMO