add anti-ghost logic

1 files changed, 58 insertions, 20 deletions

diff --git a/matrix.c b/matrix.c
index fc975a8fcc..6129f52c68 100644
--- a/matrix.c
+++ b/matrix.c
@@ -7,38 +7,36 @@
 #include "matrix.h"
 #include "print.h"
 
+// matrix is active low. (key on: 0/key off: 1)
+// row: Hi-Z(unselected)/low output(selected)
+//      PD:0,1,2,3,6,7/PC:6,7/PF:7
+// col: input w/pullup
+//      PB:0-8
+
+// matrix state buffer
 uint8_t *matrix;
-uint8_t *prev_matrix;
+uint8_t *matrix_prev;
 static uint8_t _matrix0[MATRIX_ROWS];
 static uint8_t _matrix1[MATRIX_ROWS];
 
 static uint8_t read_col(void);
+static void unselect_rows(void);
 static void select_row(uint8_t row);
 
 
+// this must be called once before matrix_scan.
 void matrix_init(void)
 {
-    // Column: input w/pullup
+    // initialize row and col
+    unselect_rows();
     DDRB = 0x00;
     PORTB = 0xFF;
 
-    // Row: Hi-Z(unselected)
-    // PD:0,1,2,3,6,7
-    // PC:6,7
-    // PF:7
-    DDRD = 0x00;
-    PORTD = 0x00;
-    DDRC = 0x00;
-    PORTC = 0x00;
-    DDRF = 0x00;
-    PORTF = 0x00;
-
-    for (int i=0; i < MATRIX_ROWS; i++) {
-        _matrix0[i] = 0xFF;
-        _matrix1[i] = 0xFF;
-    }
+    // initialize matrix state: all keys off
+    for (int i=0; i < MATRIX_ROWS; i++) _matrix0[i] = 0xFF;
+    for (int i=0; i < MATRIX_ROWS; i++) _matrix1[i] = 0xFF;
     matrix = _matrix0;
-    prev_matrix = _matrix1;
+    matrix_prev = _matrix1;
 }
 
 uint8_t matrix_scan(void)
@@ -46,25 +44,65 @@ uint8_t matrix_scan(void)
     uint8_t row, state;
     uint8_t *tmp;
 
-    tmp = prev_matrix;
-    prev_matrix = matrix;
+    tmp = matrix_prev;
+    matrix_prev = matrix;
     matrix = tmp;
 
     for (row = 0; row < MATRIX_ROWS; row++) {
         select_row(row);
         _delay_us(30);  // without this wait read unstable value.
         state = read_col();
+        unselect_rows();
 
         matrix[row] = state;
     }
     return 1;
 }
 
+bool matrix_is_modified(void) {
+    for (int i=0; i <MATRIX_ROWS; i++) {
+        if (matrix[i] != matrix_prev[i])
+            return true;
+    }
+    return false;
+}
+
+bool matrix_has_ghost(void) {
+    for (int i=0; i <MATRIX_ROWS; i++) {
+        if (matrix_has_ghost_in_row(i))
+            return true;
+    }
+    return false;
+}
+
+bool matrix_has_ghost_in_row(uint8_t row) {
+    uint8_t state = ~matrix[row];
+    // no ghost exists in case less than 2 keys on
+    if (((state - 1) & state) == 0)
+        return false;
+
+    // ghost exists in case same state as other row
+    for (int i=0; i < MATRIX_ROWS; i++) {
+        if (i == row) continue;
+        if ((~matrix[i] & state) == state) return true;
+    }
+    return false;
+}
+
 static uint8_t read_col(void)
 {
     return PINB;
 }
 
+static void unselect_rows(void) {
+    DDRD  = 0x00;
+    PORTD = 0x00;
+    DDRC  = 0x00;
+    PORTC = 0x00;
+    DDRF  = 0x00;
+    PORTF = 0x00;
+}
+
 static void select_row(uint8_t row)
 {
     switch (row) {