Teensy Mini-Midi Controller. Full post @ http://incredimike.com/blog/mini-midi-controller-using-teensyusb/

minimidi.ino

// Minimidi Teensy Midi Controller
// Mike Walker (http://incredimike.com)
// Based on code originally by Philip Cunningham (http://philipcunningham.org)
// Smoothing hacked from http://www.arduino.cc/en/Tutorial/Smoothing

// Set midi channel to send to 1
int channel = 1;

// Smoothing amount
const int numReadings = 10;

int pots_total = 2;
int pots[2] = {16, 17}; // Total Pots
//int pots[2] = {PIN_A4,PIN_A5}; // Total Pots

// Set the readings from the analog input to 0
int readings[numReadings] = {0,0,0,0,0};
int pintotal[6] = {0,0,0,0,0,0};
int average[6] = {0,0,0,0,0,0}; // Pin average
int lastreading[6] = {0,0,0,0,0,0};

// The reading_index of the current reading
int reading_index = 0;

// Running total
int total = 0;

// Button tracking
int button_total     = 2;
int button_pin[2]    = {0,1};
int button_status[2] = {HIGH,HIGH};
int button_last[2]   = {HIGH,HIGH};

// On-board LED
int led_board = 11;

void setup()
{
	// Standard midi rate
   Serial.begin(31250);
//  Serial.begin(38400); // debuggin

  // Button pins use internal pull-up resistor
  pinMode(0, INPUT_PULLUP);
  pinMode(1, INPUT_PULLUP);

  // Turn on the LED on the teensy board
  pinMode(led_board, OUTPUT);
  digitalWrite(led_board, HIGH);
}

void loop()
{

  //
	// Pots - including Smoothing functionality
  // 
	for (int i = 0; i < pots_total; i++ ) {

		// Set reading_index to zero
		reading_index = 0;

		// Loop to create average reading
		for (int j = 0; j < numReadings; j++ ){
			// Subtract the last reading
			total = total - readings[reading_index];
			// Read from the sensor
			readings[reading_index] = analogRead(pots[i]);
      
      //Serial.println(readings[reading_index]);
      
			// Add the reading to the total
			total = total + readings[reading_index];
			// Advance to the next position in the array
      reading_index++;
			pintotal[i] = total;
		}

	  // Calculate the average
	  // Divide by 8 to make between 0-127
	  average[i] = (pintotal[i]/numReadings)/8;

	  // If reading is different from the previous
	  if (lastreading[i] != average[i]){
	    usbMIDI.sendControlChange(i, average[i], channel);
//      Serial.print(i); // debugging
//      Serial.print('-'); // debugging
//      Serial.println(average[i]); // debugging
	  }
	  // Set last array value to current value
	  lastreading[i] = average[i];
	}
  
  //
  // Buttons
  //
  for (int i = 0; i < button_total; i++ ) {

    // Read in button status
    button_status[i] = digitalRead(button_pin[i]);
    
    // Check if current status is different than last check
    if (button_status[i] != button_last[i]) {

      // If different, set last check value to current.
      button_last[i] = button_status[i];
    
      // Send message to midi out. (start numbering buttons controls after pots)
      usbMIDI.sendControlChange(10+button_pin[i], button_last[i], channel);

//      Serial.println(button_pin[i]); // debugging
//      Serial.println(button_last[i]); // debugging
    }
  }

	// Delay output by 50ms
	delay(50);
}