[Keyboard] Add YDKB Grape PCB (#16661)

Co-authored-by: Drashna Jaelre <drashna@live.com>

keyboards/ydkb/grape/matrix.c

@@ -0,0 +1,96 @@
+/*
+Copyright 2022 somepin
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <stdint.h>
+#include <stdbool.h>
+#include "matrix.h"
+#include "quantum.h"
+#include "sn74x138.h"
+
+static const pin_t col_pins[MATRIX_COLS] = MATRIX_COL_PINS;
+
+/* All rows use a 74HC138 3 to 8 bit demultiplexer.
+ *
+ *     A2   A1   A0
+ *     D0   D1   D2
+ * 0:   0    0    0
+ * 1:   0    0    1
+ * 2:   0    1    0
+ * 3:   0    1    1
+ * 4:   1    0    0
+ * 5:   1    0    1
+ * 6:   1    1    0
+ */
+static void select_row(uint8_t row) {
+    sn74x138_set_addr(row);
+}
+
+static void init_pins(void) {
+    for (uint8_t x = 0; x < MATRIX_COLS; x++) {
+        setPinInputHigh(col_pins[x]);
+    }
+}
+
+static bool read_cols_on_row(matrix_row_t current_matrix[], uint8_t current_row) {
+    bool matrix_changed = false;
+
+    // Store last value of row prior to reading
+    matrix_row_t last_row_value = current_matrix[current_row];
+
+    // Start with a clear matrix row
+    current_matrix[current_row] = 0;
+
+    // Select row and wait for row selection to stabilize
+    select_row(current_row);
+    matrix_io_delay();
+
+    // For each col...
+    matrix_row_t row_shifter = MATRIX_ROW_SHIFTER;
+    for (uint8_t col_index = 0; col_index < MATRIX_COLS; col_index++) {
+
+        // Select the col pin to read (active low)
+        uint8_t pin_state = readPin(col_pins[col_index]);
+
+        // Populate the matrix row with the state of the col pin
+        current_matrix[current_row] |=  pin_state ? 0 : (row_shifter << col_index);
+    }
+    
+    // Determine if matrix changed state
+    if ((last_row_value != current_matrix[current_row]) && !(matrix_changed)) {
+        matrix_changed = true;
+    }
+
+    return matrix_changed;
+}
+
+void matrix_init_custom(void) {
+    // initialize demultiplexer
+    sn74x138_init();
+    // initialize key pins
+    init_pins();
+}
+
+bool matrix_scan_custom(matrix_row_t current_matrix[]) {
+    bool changed = false;
+
+    // Set row, read cols
+    for (uint8_t current_row = 0; current_row < MATRIX_ROWS; current_row++) {
+        changed |= read_cols_on_row(current_matrix, current_row);
+    }
+
+    return changed;
+}