Arduino As MIDI controller

/*
* MIDI Drum Kit
* -------------
* Convert Arduino to a MIDI controller using various inputs and
* the serial port as a MIDI output.
*
* This sketch is set up to send General MIDI (GM) drum notes
* on MIDI channel 1, but it can be easily reconfigured for other
* notes and channels
*
* It uses switch inputs to send MIDI notes of a fixed velocity with
* note on time determined by duration of keypress and it uses
* piezo buzzer elements as inputs to send MIDI notes of a varying velocity
* & duration, depending on forced of impulse imparted to piezo sensor.
*
* To send MIDI, attach a MIDI out jack (female DIN-5) to Arduino.
* DIN-5 pinout is: _____
* pin 2 - Gnd / \
* pin 4 - 220 ohm resistor to +5V | 3 1 | MIDI jack
* pin 5 - Arduino D1 (TX) | 5 4 |
* all other pins - unconnected \__2__/
* On my midi jack, the color of the wires for the pins are:
* 3 = n/c
* 5 = black (blue)
* 2 = red (red)
* 4 = orange (yellow)
* 1 = brown
*
* Based off of Tom Igoe's work at:
* http://itp.nyu.edu/physcomp/Labs/MIDIOutput
*
* Created 25 October 2006
* copyleft 2006 Tod E. Kurt * http://todbot.com/
*/

// what midi channel we're sending on
#define drumchan 1

// general midi drum notes
#define note_bassdrum 35
#define note_snaredrum 38
#define note_hihatclosed 42
#define note_hihatopen 44
#define note_crash 49

// define the pins we use
#define switchAPin 7
#define switchBPin 6
#define switchCPin 5
#define piezoAPin 0
#define piezoBPin 1
#define ledPin 13 // for midi out status

// analog threshold for piezo sensing
#define PIEZOTHRESHOLD 100

int switchAState = LOW;
int switchBState = LOW;
int switchCState = LOW;
int currentSwitchState = LOW;

int val,t;

void setup() {
pinMode(switchAPin, INPUT);
pinMode(switchBPin, INPUT);
pinMode(switchCPin, INPUT);
digitalWrite(switchAPin, HIGH); // turn on internal pullup
digitalWrite(switchBPin, HIGH); // turn on internal pullup
digitalWrite(switchCPin, HIGH); // turn on internal pullup

pinMode(ledPin, OUTPUT);
Serial.begin(31250); // set MIDI baud rate
}

void loop() {
// deal with switchA
currentSwitchState = digitalRead(switchAPin);
if( currentSwitchState == LOW && switchAState == HIGH ) // push
noteOn(drumchan, note_bassdrum, 100);
if( currentSwitchState == HIGH && switchAState == LOW ) // release
noteOff(drumchan, note_bassdrum, 0);
switchAState = currentSwitchState;

// deal with switchB
currentSwitchState = digitalRead(switchBPin);
if( currentSwitchState == LOW && switchBState == HIGH ) // push
noteOn(drumchan, note_snaredrum, 100);
if( currentSwitchState == HIGH && switchBState == LOW ) // release
noteOff(drumchan, note_snaredrum, 0);
switchBState = currentSwitchState;

// deal with switchC
currentSwitchState = digitalRead(switchCPin);
if( currentSwitchState == LOW && switchCState == HIGH ) // push
noteOn(drumchan, note_hihatclosed, 100);
if( currentSwitchState == HIGH && switchCState == LOW ) // release
noteOff(drumchan, note_hihatclosed, 0);
switchCState = currentSwitchState;

// deal with first piezo, this is kind of a hack
val = analogRead(piezoAPin);
if( val >= PIEZOTHRESHOLD ) {
t=0;
while(analogRead(piezoAPin) >= PIEZOTHRESHOLD/2) {
t++;
}
noteOn(1,note_hihatopen, t*2);
delay(t);
noteOff(1,note_hihatopen,0);
}

// deal with second piezos, this is kind of a hack
val = analogRead(piezoBPin);
if( val >= PIEZOTHRESHOLD ) {
t=0;
while(analogRead(piezoBPin) >= PIEZOTHRESHOLD/2) {
t++;
}
noteOn(1,note_crash, t*2);
delay(t);
noteOff(1,note_crash,0);
}
}

// Send a MIDI note-on message. Like pressing a piano key
void noteOn(byte channel, byte note, byte velocity) {
midiMsg( (0x80 | (channel<<4)), note, velocity);
}

// Send a MIDI note-off message. Like releasing a piano key
void noteOff(byte channel, byte note, byte velocity) {
midiMsg( (0x80 | (channel<<4)), note, velocity);
}

// Send a general MIDI message
void midiMsg(byte cmd, byte data1, byte data2) {
digitalWrite(ledPin,HIGH); // indicate we're sending MIDI data
Serial.print(cmd, BYTE);
Serial.print(data1, BYTE);
Serial.print(data2, BYTE);
digitalWrite(ledPin,LOW);
}