Revision 3:ed89297af2ce, committed 2014-09-22

Comitter:

andrewhead

Date:

Mon Sep 22 02:12:29 2014 +0000

Parent:

2:49e2b1273f16

Child:

4:400a042e762a

Commit message:

Read chord from pressed keys.

Changed in this revision

--- a/main.cpp	Sat Sep 20 21:19:25 2014 +0000
+++ b/main.cpp	Mon Sep 22 02:12:29 2014 +0000
@@ -6,10 +6,10 @@
 const int BUZZERS = 3;
 const int LETTERS = 27;
 
-// Flag that says whether we're waiting to collect input from other buttons
-// following one upward edge.
-bool flag = false;
-time_t startSeconds = time(NULL);
+// Collection is the time that it takes after pressing one key and then reading
+// all the keys to determine what the chord is.
+const int COLLECTION_MS = 500;
+Timer collectionTimer;
 
 InterruptIn buttons [BUTTONS] = {
     InterruptIn(D2),
@@ -43,8 +43,10 @@
     2024,   // B4
     10000000 // inaudible pitch
 };
+// Possible chords that can be played.
+// Note that 7 is no button pressed, or a 'silent' pitch.
 int chords [LETTERS][BUZZERS] = {
-    {0, 2, 4}, // single notes
+    {0, 7, 7}, // single notes
     {1, 7, 7},
     {2, 7, 7},
     {3, 7, 7},
@@ -92,7 +94,7 @@
 }
 
 void setFlag() {
-    flag = true;
+    collectionTimer.start();
 }
 
 void silenceBuzzers(void) {
@@ -108,20 +110,49 @@
     }   
 }
 
+int readChord(void) {
+    /* Detect the current chord from the keys pressed. Return int index of chord.
+       Return -1 if no chord can be found with the current keys.
+       Note that we can only read as many keys as there are buzzers, so check
+       on each key in an ascending order. */
+    int firstThreeButtons[BUZZERS] = {7, 7, 7};
+    int pressedCount = 0;
+    for (int i = 0; i < BUTTONS; i++) {
+        if (buttons[i].read() == 1) {
+            firstThreeButtons[pressedCount] = i;
+            pressedCount++;   
+        }
+        if (pressedCount >= BUZZERS) {
+            break;
+        }
+    }
+    int matchIndex = -1;
+    for (int i = 0; i < LETTERS; i++) {
+        bool chordMatches = true;
+        for (int j = 0; j < BUZZERS; j++) {
+            if (firstThreeButtons[j] != chords[i][j]) {
+                chordMatches = false;
+                break;            
+            }
+        }
+        if (chordMatches == true) {
+            matchIndex = i;
+            break;
+        }
+    }
+    pc.printf("Matched chord %d\n", matchIndex);
+    return matchIndex;
+}
+
 void waitForChord(void) {
-     /* Should be run in the main loop so that it can print */
+     /* This method should be run in the main loop so that it can print */
      while (true) {
-        time_t currentSeconds = time(NULL);
-        time_t secondsPast = currentSeconds - startSeconds;
-        if (flag == true) {
-            pc.printf("Pressed\n");
-            flag = false;
+        if (collectionTimer.read_ms() > COLLECTION_MS) {
+            collectionTimer.stop();
+            collectionTimer.reset();
+            int chordIndex = readChord();
         }
-        else {
-            pc.printf("Not pressed\n");   
-        }
-        pc.printf("Seconds: %d\n", secondsPast);
-        wait_ms(500);
+        wait_ms(10);
     }   
 }