The music synthesizer plays musical notes up to 3 octaves from low A to high A.  The synthesizer allows user to either (1) play a song from the list of pre-programmed songs in the song library or (2) create a new song into the synthesizer by entering the appropriate notes using the attached keypad.

Upon start up, the user will be prompted with the greeting: "WELCOME TO MUSIC SYNTHESIZER ..." followed by the main menu:

OPTIONS:
1: Create Song
2: Play Song Library
3: Press * to Quit
Enter Option:

Options:
1: Enter Note
2: Play Back Song
3: Clear Hist
Enter Option:

Selection "1: Enter Note" will further guide the user to enter the note(s) using the keypad.

Enter Octave (1,2,3):

"1" corresponds to the lowest octave, "2" to the middle octave and "3" to the highest octave.  Then the user must further specify if the note to be entered is a sharp or a natural note.

Sharp(Y/N)?

Answering "Y" means the note to be entered is intended to be a sharp note; "N" will indicate a natural note.  The user will then be prompted to enter the note:

Enter Note:

 Selection "2: Play Back Song" will play back the newly created song or note(s).

Selection "3: Clear Hist" clears the playback buffer so that the user can create a different song.
 

Options:
1: Nowhere Man
2: Fur Elise
3: Air
4: Silent Night
Enter Option:

 After the user selects an option, the LCD will display "Playing Song..." while the synthesizer is playing the selected song.
 

Note: the user will get "Invalid Input" prompt for any unacceptable input.

Hardware
We use an XS40 board, an 8051 chip, a keypad and an LCD.  The keypad is the input device that accept the user entry and the LCD  is the monitor display to interact with the user.  We connect the keypad to port 1 of the 8051 and the LCD to port 2 and port 3 (pins 0-1) of the 8051.  We use port 0 (pins 1-6) of the 8051 to communicate to/from the XS40 board of user input/selection. We synthesize the musical notes by generating square waves on one of the output pins of the XS40 board.  We use 12 MHz clock as the reference frequency and design a divider process to generate frequencies of the musical scale, i.e. from 440Hz to 1760Hz (low A to high A).  The processor will write to the memory mapped register a number between 0 and 35 that corresponds to to the notes A, B, C, ..., G# for 3 octaves.
 

Software
There are 6 bits connecting the 8051 and the 8031 to interact with each other.  The software on the 8051 interacts with the user and conveys the user request/input to the 8031, while the software on the 8031 executes the request and returns the status after the execution.

Note: We will refer to the 6 bits as "Select" from here on.

The playback was implemented by taking in the octave, optional sharp, and the letter of the note, and storing the note's converted signal into a playback buffer. Upon playback, an encoding to signal the start of the playback is sent to the FPGA board, and the signal for the subsequent notes are sent over the 6 bit bus, where as each note has a unique 6 bit encoding.

The 8051 follows the following logic. A finite state machine was create to implement the transitions for the various menu options. Since we interfaced two 8051's, the transitions from state to state were implement through an artificial clock cycle delay. (refer to 8051.doc for the state diagram and calc.c for the actual code):

Inactive: Select = "111111"

Get "Menu"
if Menu == CreateSong
{

Get "NoteOption"
if NoteOption == Enter Note
{

while (buffer not full and !Quit)
{

Get Octave
Get SharpNoteIndicator
Get Note (see NoteEncoding.doc for the bit patterns corresponding to the musical note A - G#)

}

}
else if NoteOption == PlayBack
{

Select = "000111"
while (!EndOfPlayBackBuffer)
{

Select = Note

}
Select = "111111"

}
else if NoteOption == ClearHistory
{

ClearPlayBackBuffer

}

}
else If Menu == Enter Song
{

Get SongOption
if (SongOption == NowhereMan) Select = "000001"
else if (SongOption == FurElise) Select = "000010"
else if (SongOption == Air) Select = "000011"
else if (SongOption == SilentNight) Select = "000100"

Wait until Select = "000000"

}
else If Menu == Quit
{

End

}

On the 8031, we download the following logic (refer to 8031.doc for the state diagram and  main.c for actual code):

Inactive: Select = "111111"

while (1)
{

if (Select = "000111")
{

Get Select = Note
Play Note

}
else if (Select = "111000")
{

Get Select
if (Select == "000001") PlayNowhereMan
else if (Select == "000010") PlayFurElise
else if (Select == "000011") PlayAir
else if (Select == "000100") PlaySilentNight
Set Select = "000000"

}

}

1.  calc.c
2.   io.c
3.   io.h
4.   main.c
5.   wrled.vhd
6.   ctrup.vhd
7.   play.vhd
8.   xs40.vhd
9.   final2.ucf
10. NoteEncoding.doc