Hardware Design

 

MIDI Interface

The midi signal output by the music instrument is sent through an optoisolator circuit to the UART of the Mega32 microcontroller.The optoisolator circuit keeps the music instrument and the sheet music generator system electrically isolated from each other so that any current spikes present in the midi output donít affect the UART.Figure 3 shows the hardware diagram.

 

 

Figure 3: Midi Input Circuit.The MIDI cable pins are color coordinated to correspond to the color of the wires in the cable.

 

TV Interface

The TV screen is painted by proper voltage waveforms sent by the mcu through an RCA cable.We use a simple 2 bit DAC to convert the outputs of pin 5 and 6 of PORTD to the proper voltage signals.The sync pulse corresponds to 0V voltage level, black corresponds to .3V, and white is around 1V.The resistor values used in our DAC results in:

†††††††

Signal

††† Pin 5

Pin 6

Voltage input to the TV

sync

0

0

0V

black

 

1

0

=.24V

white

1

1

+= 1.06V

†††††††††††††††††††††††††††††††

 

where a value of 1 for the pin corresponds to Vcc or 5V.When the screen is painted, Pin 5 is set to 1 and Pin 6 is set to 0 if the pixel should be black and 1 if the pixel should be white.At the end of each screen line Pin 6 is set to 0 and Pin 5 is set to 0 in the ISR for sync-ing.

 

User and PC Interface

The user interacts with the sheet music generator system using a keypad and through a GUI.The keypad is wired as shown in Appendix B.Key D enables transmission to the PC and key # resets the sheet music.

 

*please see Appendix B for further detail