Add sym_defer_pr debouncer type (#14948)

1 files changed, 72 insertions, 0 deletions

diff --git a/quantum/debounce/sym_defer_pr.c b/quantum/debounce/sym_defer_pr.c
new file mode 100644
index 0000000000..8b33acc6a2
--- /dev/null
+++ b/quantum/debounce/sym_defer_pr.c
@@ -0,0 +1,72 @@
+/*
+Copyright 2021 Chad Austin <chad@chadaustin.me>
+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/>.
+*/
+
+/*
+Symmetric per-row debounce algorithm. Changes only apply when
+DEBOUNCE milliseconds have elapsed since the last change.
+*/
+
+#include "matrix.h"
+#include "timer.h"
+#include "quantum.h"
+#include <stdlib.h>
+
+#ifndef DEBOUNCE
+#    define DEBOUNCE 5
+#endif
+
+static uint16_t last_time;
+// [row] milliseconds until key's state is considered debounced.
+static uint8_t* countdowns;
+// [row]
+static matrix_row_t* last_raw;
+
+void debounce_init(uint8_t num_rows) {
+    countdowns = (uint8_t*)calloc(num_rows, sizeof(uint8_t));
+    last_raw   = (matrix_row_t*)calloc(num_rows, sizeof(matrix_row_t));
+
+    last_time = timer_read();
+}
+
+void debounce_free(void) {
+    free(countdowns);
+    countdowns = NULL;
+    free(last_raw);
+    last_raw = NULL;
+}
+
+void debounce(matrix_row_t raw[], matrix_row_t cooked[], uint8_t num_rows, bool changed) {
+    uint16_t now       = timer_read();
+    uint16_t elapsed16 = TIMER_DIFF_16(now, last_time);
+    last_time          = now;
+    uint8_t elapsed    = (elapsed16 > 255) ? 255 : elapsed16;
+
+    uint8_t* countdown = countdowns;
+
+    for (uint8_t row = 0; row < num_rows; ++row, ++countdown) {
+        matrix_row_t raw_row = raw[row];
+
+        if (raw_row != last_raw[row]) {
+            *countdown    = DEBOUNCE;
+            last_raw[row] = raw_row;
+        } else if (*countdown > elapsed) {
+            *countdown -= elapsed;
+        } else if (*countdown) {
+            cooked[row] = raw_row;
+            *countdown  = 0;
+        }
+    }
+}
+
+bool debounce_active(void) { return true; }