Started following some tutorial on att85 usi. Downloaded example code from make avr book.

Make AVR Examples/Chapter05_Serial-IO/serialOrgan/serialOrgan.c

@@ -0,0 +1,74 @@
+/*
+
+serialOrgan.c
+
+Reads a character in serial from the keyboard, plays a note.
+
+See organ.h for pin defines and other macros
+See organ.c (and include it in the Makefile) for playNote() and rest()
+
+*/
+
+// ------- Preamble -------- //
+#include <avr/io.h>
+#include <util/delay.h>
+#include "organ.h"
+#include "scale16.h"
+#include "pinDefines.h"
+#include "USART.h"
+
+#define NOTE_DURATION     0xF000        /* determines long note length */
+
+int main(void) {
+
+  // -------- Inits --------- //
+  SPEAKER_DDR |= (1 << SPEAKER);                 /* speaker for output */
+  initUSART();
+  printString("----- Serial Organ ------\r\n");
+
+  char fromCompy;                        /* used to store serial input */
+  uint16_t currentNoteLength = NOTE_DURATION / 2;
+  const uint8_t keys[] = { 'a', 'w', 's', 'e', 'd', 'f', 't',
+    'g', 'y', 'h', 'j', 'i', 'k', 'o',
+    'l', 'p', ';', '\''
+  };
+  const uint16_t notes[] = { G4, Gx4, A4, Ax4, B4, C5, Cx5,
+    D5, Dx5, E5, F5, Fx5, G5, Gx5,
+    A5, Ax5, B5, C6
+  };
+  uint8_t isNote;
+  uint8_t i;
+
+  // ------ Event loop ------ //
+  while (1) {
+
+                                                            /* Get Key */
+    fromCompy = receiveByte();      /* waits here until there is input */
+    transmitByte('N');     /* alert computer we're ready for next note */
+
+                                                         /* Play Notes */
+    isNote = 0;
+    for (i = 0; i < sizeof(keys); i++) {
+      if (fromCompy == keys[i]) {       /* found match in lookup table */
+        playNote(notes[i], currentNoteLength);
+        isNote = 1;                  /* record that we've found a note */
+        break;                               /* drop out of for() loop */
+      }
+    }
+
+                      /* Handle non-note keys: tempo changes and rests */
+    if (!isNote) {
+      if (fromCompy == '[') {                   /* code for short note */
+        currentNoteLength = NOTE_DURATION / 2;
+      }
+      else if (fromCompy == ']') {               /* code for long note */
+        currentNoteLength = NOTE_DURATION;
+      }
+      else {                                /* unrecognized, just rest */
+        rest(currentNoteLength);
+      }
+    }
+
+  }                                                  /* End event loop */
+  return 0;
+}