Final project.


Here lies thy documentation for the final project, the Jukebox.



Ideation


This project is inspired by self playing pianos.

Player piano from wikipedia:

A melodica is a small piano with fewer keys.

Melodica played using midi.





Midi file format


Midi timings

A midi event will have the change in time from the previous event and the event data.

Example midi data in hexadecimal.

Delta time is calculated from the tempo and time signature of the midi track.

Source

Midi commands

Midi event flow.

Midi message structure.

Midi commands and their hex codes. Only note on and note off commands will be processed. Other commands are ignored.

A midi command also includes the note and velocity. The velocity is ignored and only the note and channel is used.

Source

Midi notes

128 midi notes and their corresponding keys. Source

MIDI note number Key number (Organ) Key number (Piano) Note names (English) Note names (German) Frequency (Equal tuning at 440 Hz)
top of MIDI tuning range     G#9/Ab9 gis’’’’’’/ges’’’’’’ 13289.75
127     G9 g’’’’’’ 12543.85
126     F#9/Gb9 fis’’’’’’/ges’’’’’’ 11839.82
125     F9 f’’’’’’ 11175.30
124     E9 e’’’’’’ 10548.08
123     D#9/Eb9 dis’’’’’’/es’’’’’’ 9956.06
122     D9 d’’’’’’ 9397.27
121     C#9/Db9 cis’’’’’’/des’’’’’’ 8869.84
120     C9 c’’’’’’ 8372.02
119     B8 h’’’’’ 7902.13
118     A#8/Bb8 ais’’’’’/b’’’’’ 7458.62
117     A8 a’’’’’ 7040.00
116     G#8/Ab8 gis’’’’’/ges’’’’’ 6644.88
115     G8 g’’’’’ 6271.93
114     F#8/Gb8 fis’’’’’/ges’’’’’ 5919.91
113     F8 f’’’’’ 5587.65
112     E8 e’’’’’ 5274.04
111     D#8/Eb8 dis’’’’’/es’’’’’ 4978.03
110     D8 d’’’’’ 4698.64
109     C#8/Db8 cis’’’’’/des’’’’’ 4434.92
108   88 C8 c’’’’’ 4186.01
107   87 B7 h’’’’ 3951.07
106   86 A#7/Bb7 ais’’’’/b’’’’ 3729.31
105   85 A7 a’’’’ 3520.00
104   84 G#7/Ab7 gis’’’’/ges’’’’ 3322.44
103   83 G7 g’’’’ 3135.96
102   82 F#7/Gb7 fis’’’’/ges’’’’ 2959.96
101   81 F7 f’’’’ 2793.83
100   80 E7 e’’’’ 2637.02
99   79 D#7/Eb7 dis’’’’/es’’’’ 2489.02
98   78 D7 d’’’’ 2349.32
97   77 C#7/Db7 cis’’’’/des’’’’ 2217.46
96 61 76 C7 c’’’’ 2093.00
95 60 75 B6 h’’’ 1975.53
94 59 74 A#6/Bb6 ais’’’/b’’’ 1864.66
93 58 73 A6 a’’’ 1760.00
92 57 72 G#6/Ab6 gis’’’/as’’’ 1661.22
91 56 71 G6 g’’’ 1567.98
90 55 70 F#6/Gb6 fis’’’/ges’’’ 1479.98
89 54 69 F6 f’’’ 1396.91
88 53 68 E6 e’’’ 1318.51
87 52 67 D#6/Eb6 dis’’’/es’’’ 1244.51
86 51 66 D6 d’’’ 1174.66
85 50 65 C#6/Db6 cis’’’/des’’’ 1108.73
84 49 64 C6 c’’’ 1046.50
83 48 63 B5 h’’ 987.77
82 47 62 A#5/Bb5 ais’’/b’’ 932.33
81 46 61 A5 a’’ 880.00
80 45 60 G#5/Ab5 gis’’/as’’ 830.61
79 44 59 G5 g’’ 783.99
78 43 58 F#5/Gb5 fis’’/ges’’ 739.99
77 42 57 F5 f’’ 698.46
76 41 56 E5 e’’ 659.26
75 40 55 D#5/Eb5 dis’’/es’’ 622.25
74 39 54 D5 d’’ 587.33
73 38 53 C#5/Db5 cis’’/des’’ 554.37
72 37 52 C5 c’’ 523.25
71 36 51 B4 h’ 493.88
70 35 50 A#4/Bb4 ais’/b’ 466.16
69 34 49 A4 concert pitch a’ Kammerton 440.00
68 33 48 G#4/Ab4 gis’/as’ 415.30
67 32 47 G4 g’ 392.00
66 31 46 F#4/Gb4 fis’/ges’ 369.99
65 30 45 F4 f’ 349.23
64 29 44 E4 e’ 329.63
63 28 43 D#4/Eb4 dis’/es’ 311.13
62 27 42 D4 d’ 293.66
61 26 41 C#4/Db4 cis’/des’ 277.18
60 25 40 C4 (middle C) c’ (Schloss-C) 261.63
59 24 39 B3 h 246.94
58 23 38 A#3/Bb3 ais/b 233.08
57 22 37 A3 a 220.00
56 21 36 G#3/Ab3 gis/as 207.65
55 20 35 G3 g 196.00
54 19 34 F#3/Gb3 fis/ges 185.00
53 18 33 F3 f 174.61
52 17 32 E3 e 164.81
51 16 31 D#3/Eb3 dis/es 155.56
50 15 30 D3 d 146.83
49 14 29 C#3/Db3 cis/des 138.59
48 13 28 C3 c 130.81
47 12 27 B2 H 123.47
46 11 26 A#2/Bb2 Ais/B 116.54
45 10 25 A2 A 110.00
44 9 24 G#2/Ab2 Gis/As 103.83
43 8 23 G2 G 98.00
42 7 22 F#2/Gb2 Fis/Ges 92.50
41 6 21 F2 F 87.31
40 5 20 E2 E 82.41
39 4 19 D#2/Eb2 Dis/Es 77.78
38 3 18 D2 D 73.42
37 2 17 C#2/Db2 Cis/Des 69.30
36 1 16 C2 C 65.41
35   15 B1 H1 61.74
34   14 A#1/Bb1 Ais1/b1 58.27
33   13 A1 A1 55.00
32   12 G#1/Ab1 Gis1/As1 51.91
31   11 G1 G1 49.00
30   10 F#1/Gb1 Fis1/Ges1 46.25
29   9 F1 F1 43.65
28   8 E1 E1 41.20
27   7 D#1/Eb1 Dis1/Es1 38.89
26   6 D1 D1 36.71
25   5 C#1/Db1 Cis1/Des1 34.65
24   4 C1 C1 32.70
23   3 B0 H2 30.87
22   2 A#0/Bb0 Ais2/B2 29.14
21   1 A0 A2 27.50
20         25.96
19         24.50
18         23.12
17         21.83
16         20.60
15         19.45
14         18.35
13         17.32
12         16.35
11         15.43
10         14.57
9         13.75
8         12.98
7         12.25
6         11.56
5         10.91
4         10.30
3         9.72
2         9.18
1         8.66
0         8.18


Cad Design


Finished cad design.

Servos are mounted in front.

Servos line up with keys.

Slots constraint the linkages.

LCD, SD card and the rotary encoder will be here.

Back view. The hole on the right was originally intended for a sever fan to supply the air pressure to play the melodica. It was not powerfull enough.

Servos are mounted in foam to absorb vibrations.



Molding and casting


CNC milling

Milling has started.

Toolpath.

Pocketing has begun.

Finishing passes.

Milling is done.

Close up of finished mold.

CNC milling underway.



Molding

Silicone is poured in at an angle.

Silicone pour is done.

Foam is broken off.

Finished mold.



Casting

Polyurathane is poured into the mold.

There are some overflows and spills.

Once hard enough they can be cut off with a knife.

Heat makes the polyurathane cure faster.

The mold is bent to demold the parts.

Parts are pushed out of the mold.

Cast parts.

Some parts did not reach the bottom of the mold.

One batch was not mixed well. The polyurathane did not set even after a day.

Holes are drilled into the ends.

Finished part with hole.



CNC milling


First attempt milling.

Facing the back.

Milling is done.

The first attempt has an inconsistent height because of the second side facing. The second attempt only has operations on one side.

Second attempt at milling left side.

Right side milling.



3D printing


3D printing of standoffs.

3D printing is done.

Printing in progress.

Another 3d printed part, holddown clamps for the melodica.



Laser cutting




Pcb design


This section documents printed circuit board design in kicad and milling.

Shift register board design


Shift registers convert serial data to parrallel data. Up to 40 outputs(5 shift registers) can be driven using only 5 pins.


This is the Kicad schematic design.

PCB design in Kicad.

Front side PCB view.

Back side PCB view.

Front copper toolpath in Flatcam.

Back copper toolpath in Flatcam.



Microcontroller board design


This is the microcontroller schematic.

This is the PCB design in kicad.

PCB 3d view in kicad.

Toolpaths in Flatcam.



Shift register board milling


Milling has started for the shift register board.

The back copper is isolation milled.

Excess copper is being removed.

Front copper milling is started.

Milling continues...

Isolation milling is done.

The holes are milled.

Finished holes.

Finished front copper board.

Two finished sides of the PCB.

Shift registers are soldered on.

Pcb is populated.

Pin headers are solder on.

Back copper view.



Microcontroller board milling


Milling for the microcontoller board has started.

Toolpath of microcontroller board.

FR4 is used for this PCB. Water is used to prevent fiberglass dust from getting into the air and makes the cut smoother.

Dust generated is trapped in the water.

Video of PCB milling.

The PCB is milled, board outline and holes are cut.

Finishd PCB.

One part did not cut through.

This was fixed with a penknife.

Some copper was removed near the atmega chip.

Finished, wired microcontroller board.

Soldered microcontroller.





Programming


The LCD and rotary encoder ate wired up.

Rotory encoder programming


The rotary encoder used is a pulse rotary encoder. The clock pulse is polled by the microcontroller when needed. Turning the rotary encoder scrolls the selection menu and clicking the rotary encoder selects the midi track.

Program to read rotary encoder.

Endoder count printed on serial monitor.



LCD programming


The LCD used is a 20x4 LCD. It communicates with the m328 through a 4 bit parallel interface.

Modified example program.

LCD hello world.



SD card programming


FatFs is used to communicate with the SD card. Fatfs is used because it can use file names longer than 8.5 characters. Limiting the file name lengths to 8 chars and a file extension made long file names hard to read. The fat FS library is used to buffer the data from the SD card in 512 byte blocks.

Code to read SD card data.




Code for menu navigation.

Menu displayed on LCD.

Menu navigation.



Midi file processing


MD_midi library is used to buffer the midi data read from the SD card. The midi used is standard midi file type 0. The type 0 midi file only has 1 track and all channel events are on that one track, making it easier to read the midi file as all the data is in a continuous ckunk. Md_midi also generates clock timings using timer 0. The clock timings is determined using the rate of the music. MD_midi generates the midi events at the right time and sends the midi data through UART at a baud rate of 19200 to the other two microcontrollers.

Code for midi callback.



Assembly triangle wave generator


The ask synth library is used. It generates a polyphonic tone using triangle waves. Timer 2 is used with a prescaller of 4 to generate a interrupt at 15.6 khz. The microcontroller is programmed for up to 16 tones. Ask synth uses assembly and is programmed for the atmega328p. A speaker is used to generate the notes that could not be played by the melodica. Midi supports 128 notes and all notes can be played by the speaker. A l289 motor driver is used to drive the speaker. A second microcontroller is used because there was not enough memory and the microcontroller would reset itself.

Test code.

Assembly source code.

Configurations needed to be set before compile.

Example waveform generated by asmsynth. Source:Sezam

Example sketch.



UART buffering


The standard uart buffer of 64 bytes is not enough because the program is not fast enough to read the buffer before it is full.

The standard uart buffer size is 64.

Recieve buffer size is increades to 256 and transmit is reduced to 16.



ADSR envelope


An adsr envelope is used to make the notes sound more realistic. The adsr envelope use timer 0 for the clock.



Shift register programming


The shift register is used as the atmega328 dose not have enough pins to control 37 servos at once. The shift register converte serial data to parrallel data.

digitalWriteFast is a macro that compiles into a single assembly instrucion.

Shift register test with LEDs.



Servo timer interrupts


The third microcontroller controls the servo motors. Timer 1 compare and overflow interrupts are used to generate a pulse for the servo motor. The melodica only cover notes 35 hex to 59 hex. There is a 5 A poly fuse to limit the current into the servos so that in case too many servos move at once, it would not draw too much current. This polyfuse has been accidentaly tested and verified to be working. A third microcontroller was used because the second microcontroller uses too many of it cycles inside that timer 2 interrupt vector. There are only 1024 cycles between timer 2 interrupts and it was not enough. The timer 2 interrupt took too many cycles and caused the servo timings generated by timer 1 to be inconsistent. The srevos draw the most current. A 12v 3 a wall adaptor is used to supply the power. It goes through a 5v 5a buck convertor that supplies the microcontrollers and servos.

Timer 1 interrupts are used to drive the servos.

Timer 1 setup.

Servo test.

Servo test 2.



Bootloader burn


A bootloader is needed to program the atmega328 chip using uart. The standard programming via ISP does not. Fuses need to be set for the external crystal.

The chip is first tested with AVRdude.

Minicore is used because the standard arduino core dosent include the atmega328 chip.

The fuses and bootloader are burnt.



Source files


All source files including test code.

Download.



Slide




Project video




Full test





Testing


Volume Midi Track Test result
Minecraft Volume Alpha Calm Good
Key Good
Living Mice Missed notes
Sweden Stuck notes
Minecraft Volume Beta Mall Stuck notes
Mellohi Good
Wait Good
Undertale Home Good
Once Upon A Time Good
Undertale Stuck notes
Misc Hello World Stuck notes
Eight Melodies Good

Minecraft Volume Alpha


Calm


Key


Living Mice


Sweden


Minecraft Volume Beta


Mall


Mellohi


Wait


Undertale


Home


Once Upon A Time


Undertale


Hello World




Eight melodies






Finished


Wires bundled and tied. Boards mounted with 3d printed mounts.

A foot pump is used to supply air pressure. Initially a server fan was used, but it was not powerful enough and was too loud.

Balloon to smooth out air pressure.

Servo pressing keys.



Its Done!

That's all folks!