MIDI-out and MCP23017 sketch

source/sketches/testing/MIDI-Out_MCP23017.ino

@@ -0,0 +1,48 @@
+#include <Wire.h>
+
+//helper to check MCP23017 input
+#define BIT_IS_SET(i, bits)  (1 << i & bits)
+
+//array for the 8 inputs of bank A of MCP23017
+boolean button[8];
+
+void setup() {
+	//set MIDI baudrate
+	Serial.begin(31250);
+	//start I2C
+	Wire.begin();
+}
+
+void loop() {
+	//0x20 address of MCP23017 (A0,A1,A2 to ground)
+	Wire.beginTransmission(0x20);
+	Wire.write(0x12); // set MCP23017 memory pointer to GPIOA address
+	Wire.endTransmission();
+	Wire.requestFrom(0x20, 1); // request one byte of data from MCP20317
+	int inputs = Wire.read();
+	delayMicroseconds(10);
+	int i;
+	for(i=0;i<8;i++) {
+		//checkk for every input if its set
+		if (BIT_IS_SET(i,inputs)) {
+			//only send Note-on, when button was not pressed before
+			if(!button[i]) {
+				button[i] = true;
+				midiSignal(144,60+i,115);
+			}
+		} else {
+		//if not pressed, only send Note-off when button was pressed before
+			if(button[i]) {
+				button[i] = false;
+				midiSignal(128,60+i,0);
+			}
+		}
+	}  
+}
+
+//send MIDI signal
+void midiSignal(byte b1, byte b2, byte b3) {
+	Serial.write(b1);
+	Serial.write(b2);
+	Serial.write(b2);
+}