README and song position pointer message update

Author: kevinstadler

README.md

@@ -2,14 +2,16 @@
 
 This sketch implements a [MIDI beat clock](https://en.wikipedia.org/wiki/MIDI_beat_clock) driver which can be controlled by tapping a button or pedal (such as a digital keyboard sustain pedal) connected to the Arduino. Holding the button/pedal down for 1 second stops the beat messages until a new tempo is tapped in.
 
-The default pin setting I used for building a compact unit out of an Arduino Nano is as follows:
+The default pinout I used for building a compact unit out of an [Arduino Nano](http://www.pighixxx.com/test/wp-content/uploads/2014/11/nano.png) is as follows:
 
 * External power supply (5-20V) to pins `VIN` and `GND`
 * Button or pedal to pins `GND` and `14` aka `A0` (used in `INPUT_PULLUP` mode)
-* MIDI DIN connector pin 2 to Arduino `GND`
+* [MIDI DIN connector](https://en.wikipedia.org/wiki/MIDI#Connectors) pin 2 to Arduino `GND`
 * MIDI DIN connector pin 4 to Arduino pin `5V` *through a 220 Ohm resistor*
 * MIDI DIN connector pin 5 to Arduino pin `10` *through a 220 Ohm resistor*
-* Status LED to Arduino pin `6` (through a suitable resistor)
+* Status LED to Arduino pin `6` (through a suitable resistor) and `GND`
+
+Since the MIDI messages are not sent via the hardware serial interface, it is also possible to run the Arduino off USB power and use the normal Serial monitor for debugging.
 
 <img src="https://raw.githubusercontent.com/kevinstadler/arduino-tap-midi-clock/master/arduino-tap-midi-clock.jpg" alt="Arduino Tap Midi Clock hardware" title="Arduino Tap Midi Clock hardware" align="center" width="100%" />
 

miditap.ino

@@ -112,12 +112,8 @@ void setClockPulse() {
     clockPulseActive = true;
     Timer1.attachInterrupt(sendClockPulse, clockPeriod);
     // syncing the onset of the arpeggiator with the actual time of the tap (rather
-    // than just the tempo of the tapping) would be nice, but a midi start alone
-    // sadly doesn't do the trick
-    // TODO: try out the Song Position Pointer message to reset arpeggiator:
-    //Midi.write(0xF2);
-    //Midi.write(0x00);
-    //Midi.write(0x00);
+    // than just the *tempo* of the tapping) would be nice, but neither a MIDI start
+    // nor a Song Position Pointer message appear to reset the arpeggiator on my Korg
   }
 }