The onboard LED uses MPs 11, 12 and 13. See post #369 for more information. These 3 MPs are brought out on the 30 pin connector (see attachment) so in theory you could remove the on-board LED and use the signals on the the 30 pin connector. The MP pins aren't designed to drive LEDs directly, this is from the ADAU1452 datasheet: "The digital output pins are not designed for static current draw; do not use these pins to drive LEDs directly". You'll need some LED drive circuitry between the MP pins and LEDs.