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Audio Module Controlled by FPGA

Audio Module Controlled by FPGAThe project consists to control audio module with a programmable device the FPGA. We have chosen an excerpt from Ode to Joy from the Ninth Ludwig van Beethoven Symphony to provide an example of application. The next level of implementation was the implement a synthesizer using the PC keyboard.

The FPGA model used is a manufacturer EPF8282A ALTERA. This family component is FLEX 8000, provides 282 records, 208 logic cells and 64 pins of I/O.

 

 

Program Description

The program is developed in VHDL with a view to implementation on an EPF8282A. With the optimized program code have been used 202 of the 208 logical cells. It consists of the following processes:

Program Description

State Machine

Make the audio control module implemented in four states:

  • Melody ROM update, which in turn causes the update of Notes ROMs, Times and Volumes
  • Operations on the Port B: The volume on the top and the bell in the low.
  • Update the data on Port A and B.
  • Time delay function of the note.

Notes ROM

For coding of melody proposal has only been necessary to use SOL6 an eighth of a SOL7 without sustained, equivalent to 8 elements and is therefore 3 bits.

ROM Timing

The time required have been 4 (white, black dot, black and eighth), therefore with 2 bits

Volume ROM

In our case all the notes have the same volume (piano), with a bit is enough.

Melody ROM

Encodes the score. The method for doing this is almost direct and thanks to the three previous ROMs define the characteristic elements of musical notation.

The first codification of the notes could be the port module audio, but then use 16 bits for each note and the coding method austerity.

With the proposed coding scheme uses 6 bits for each note and encoding method is much closer to the shape of musical thought. This method is much better when the size of the melody, and that the first 3 ROMs cause memory using a fixed minimum. Details of the melody are organized into four ROMs. Three ROMs encode the notes, volumes and times respectively, and the remaining ROM encodes the melody.

[Year: 2008; Market: professional audio; Product group: audio]

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