Eager Per Row Debouncing added (added to Ergodox) (#5498)

* Implemented Eager Per Row debouncing algorithm.

Good for when fingers can only press one row at a time (e.g. when keyboard is wired so that "rows" are vertical)

* Added documentation for eager_pr

* Ported ergodox_ez to eager_pr debouncing.

* Removed check for changes in matrix_scan.

* Added further clarification in docs.

* Accidental merge with ergodox_ez

* Small cleanup in eager_pr

* Forgot to debounce_init - this would probably cause seg-faults.

5 files changed, 302 insertions, 264 deletions

diff --git a/docs/feature_debounce_type.md b/docs/feature_debounce_type.md
index 5d4343f08..38eca3f37 100644
--- a/docs/feature_debounce_type.md
+++ b/docs/feature_debounce_type.md
@@ -33,7 +33,10 @@ The debounce code is compatible with split keyboards.
 # Changing between included debouncing methods
 You can either use your own code, by including your own debounce.c, or switch to another included one.
 Included debounce methods are:
-* eager_pk - debouncing per key. On any state change, response is immediate, followed by ```DEBOUNCE_DELAY``` millseconds of no further input for that key
+* eager_pr - debouncing per row. On any state change, response is immediate, followed by locking the row ```DEBOUNCE_DELAY``` milliseconds of no further input for that row. 
+For use in keyboards where refreshing ```NUM_KEYS``` 8-bit counters is computationally expensive / low scan rate, and fingers usually only hit one row at a time. This could be
+appropriate for the ErgoDox models; the matrix is rotated 90°, and hence its "rows" are really columns, and each finger only hits a single "row" at a time in normal use.
+* eager_pk - debouncing per key. On any state change, response is immediate, followed by ```DEBOUNCE_DELAY``` milliseconds of no further input for that key
 * sym_g - debouncing per keyboard. On any state change, a global timer is set. When ```DEBOUNCE_DELAY``` milliseconds of no changes has occured, all input changes are pushed.
 
 
diff --git a/keyboards/ergodox_ez/matrix.c b/keyboards/ergodox_ez/matrix.c
index 860cf7b22..97f764113 100644
--- a/keyboards/ergodox_ez/matrix.c
+++ b/keyboards/ergodox_ez/matrix.c
@@ -33,14 +33,14 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "debug.h"
 #include "util.h"
 #include "matrix.h"
+#include "debounce.h"
 #include QMK_KEYBOARD_H
 #ifdef DEBUG_MATRIX_SCAN_RATE
-#include  "timer.h"
+#  include "timer.h"
 #endif
 
 /*
- * This constant define not debouncing time in msecs, but amount of matrix
- * scan loops which should be made to get stable debounced results.
+ * This constant define not debouncing time in msecs, assuming eager_pr.
  *
  * On Ergodox matrix scan rate is relatively low, because of slow I2C.
  * Now it's only 317 scans/second, or about 3.15 msec/scan.
@@ -52,26 +52,17 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #ifndef DEBOUNCE
-#   define DEBOUNCE     5
+#  define DEBOUNCE 5
 #endif
 
 /* matrix state(1:on, 0:off) */
-static matrix_row_t matrix[MATRIX_ROWS];
-/*
- * matrix state(1:on, 0:off)
- * contains the raw values without debounce filtering of the last read cycle.
- */
-static matrix_row_t raw_matrix[MATRIX_ROWS];
-
-// Debouncing: store for each key the number of scans until it's eligible to
-// change.  When scanning the matrix, ignore any changes in keys that have
-// already changed in the last DEBOUNCE scans.
-static uint8_t debounce_matrix[MATRIX_ROWS * MATRIX_COLS];
+static matrix_row_t raw_matrix[MATRIX_ROWS];  // raw values
+static matrix_row_t matrix[MATRIX_ROWS];      // debounced values
 
 static matrix_row_t read_cols(uint8_t row);
-static void init_cols(void);
-static void unselect_rows(void);
-static void select_row(uint8_t row);
+static void         init_cols(void);
+static void         unselect_rows(void);
+static void         select_row(uint8_t row);
 
 static uint8_t mcp23018_reset_loop;
 // static uint16_t mcp23018_reset_loop;
@@ -81,197 +72,137 @@ uint32_t matrix_timer;
 uint32_t matrix_scan_count;
 #endif
 
+__attribute__((weak)) void matrix_init_user(void) {}
 
-__attribute__ ((weak))
-void matrix_init_user(void) {}
+__attribute__((weak)) void matrix_scan_user(void) {}
 
-__attribute__ ((weak))
-void matrix_scan_user(void) {}
+__attribute__((weak)) void matrix_init_kb(void) { matrix_init_user(); }
 
-__attribute__ ((weak))
-void matrix_init_kb(void) {
-  matrix_init_user();
-}
+__attribute__((weak)) void matrix_scan_kb(void) { matrix_scan_user(); }
 
-__attribute__ ((weak))
-void matrix_scan_kb(void) {
-  matrix_scan_user();
-}
-
-inline
-uint8_t matrix_rows(void)
-{
-    return MATRIX_ROWS;
-}
+inline uint8_t matrix_rows(void) { return MATRIX_ROWS; }
 
-inline
-uint8_t matrix_cols(void)
-{
-    return MATRIX_COLS;
-}
+inline uint8_t matrix_cols(void) { return MATRIX_COLS; }
 
-void matrix_init(void)
-{
-    // initialize row and col
+void matrix_init(void) {
+  // initialize row and col
 
-    mcp23018_status = init_mcp23018();
+  mcp23018_status = init_mcp23018();
 
+  unselect_rows();
+  init_cols();
 
-    unselect_rows();
-    init_cols();
-
-    // initialize matrix state: all keys off
-    for (uint8_t i=0; i < MATRIX_ROWS; i++) {
-        matrix[i] = 0;
-        raw_matrix[i] = 0;
-        for (uint8_t j=0; j < MATRIX_COLS; ++j) {
-            debounce_matrix[i * MATRIX_COLS + j] = 0;
-        }
-    }
+  // initialize matrix state: all keys off
+  for (uint8_t i = 0; i < MATRIX_ROWS; i++) {
+    matrix[i]     = 0;
+    raw_matrix[i] = 0;    
+  }
 
 #ifdef DEBUG_MATRIX_SCAN_RATE
-    matrix_timer = timer_read32();
-    matrix_scan_count = 0;
+  matrix_timer      = timer_read32();
+  matrix_scan_count = 0;
 #endif
-
-    matrix_init_quantum();
-
+  debounce_init(MATRIX_ROWS);
+  matrix_init_quantum();
 }
 
 void matrix_power_up(void) {
-    mcp23018_status = init_mcp23018();
+  mcp23018_status = init_mcp23018();
 
-    unselect_rows();
-    init_cols();
+  unselect_rows();
+  init_cols();
 
-    // initialize matrix state: all keys off
-    for (uint8_t i=0; i < MATRIX_ROWS; i++) {
-        matrix[i] = 0;
-    }
+  // initialize matrix state: all keys off
+  for (uint8_t i = 0; i < MATRIX_ROWS; i++) {
+    matrix[i] = 0;
+  }
 
 #ifdef DEBUG_MATRIX_SCAN_RATE
-    matrix_timer = timer_read32();
-    matrix_scan_count = 0;
+  matrix_timer      = timer_read32();
+  matrix_scan_count = 0;
 #endif
 }
 
-// Returns a matrix_row_t whose bits are set if the corresponding key should be
-// eligible to change in this scan.
-matrix_row_t debounce_mask(matrix_row_t rawcols, uint8_t row) {
-  matrix_row_t result = 0;
-  matrix_row_t change = rawcols ^ raw_matrix[row];
-  raw_matrix[row] = rawcols;
-  for (uint8_t i = 0; i < MATRIX_COLS; ++i) {
-    if (debounce_matrix[row * MATRIX_COLS + i]) {
-      --debounce_matrix[row * MATRIX_COLS + i];
-    } else {
-      result |= (1 << i);
-    }
-    if (change & (1 << i)) {
-      debounce_matrix[row * MATRIX_COLS + i] = DEBOUNCE;
+uint8_t matrix_scan(void) {
+  if (mcp23018_status) {  // if there was an error
+    if (++mcp23018_reset_loop == 0) {
+      // if (++mcp23018_reset_loop >= 1300) {
+      // since mcp23018_reset_loop is 8 bit - we'll try to reset once in 255 matrix scans
+      // this will be approx bit more frequent than once per second
+      print("trying to reset mcp23018\n");
+      mcp23018_status = init_mcp23018();
+      if (mcp23018_status) {
+        print("left side not responding\n");
+      } else {
+        print("left side attached\n");
+        ergodox_blink_all_leds();
+      }
     }
   }
-  return result;
-}
-
-matrix_row_t debounce_read_cols(uint8_t row) {
-  // Read the row without debouncing filtering and store it for later usage.
-  matrix_row_t cols = read_cols(row);
-  // Get the Debounce mask.
-  matrix_row_t mask = debounce_mask(cols, row);
-  // debounce the row and return the result.
-  return (cols & mask) | (matrix[row] & ~mask);;
-}
-
-uint8_t matrix_scan(void)
-{
-    if (mcp23018_status) { // if there was an error
-        if (++mcp23018_reset_loop == 0) {
-        // if (++mcp23018_reset_loop >= 1300) {
-            // since mcp23018_reset_loop is 8 bit - we'll try to reset once in 255 matrix scans
-            // this will be approx bit more frequent than once per second
-            print("trying to reset mcp23018\n");
-            mcp23018_status = init_mcp23018();
-            if (mcp23018_status) {
-                print("left side not responding\n");
-            } else {
-                print("left side attached\n");
-                ergodox_blink_all_leds();
-            }
-        }
-    }
 
 #ifdef DEBUG_MATRIX_SCAN_RATE
-    matrix_scan_count++;
+  matrix_scan_count++;
 
-    uint32_t timer_now = timer_read32();
-    if (TIMER_DIFF_32(timer_now, matrix_timer)>1000) {
-        print("matrix scan frequency: ");
-        pdec(matrix_scan_count);
-        print("\n");
+  uint32_t timer_now = timer_read32();
+  if (TIMER_DIFF_32(timer_now, matrix_timer) > 1000) {
+    print("matrix scan frequency: ");
+    pdec(matrix_scan_count);
+    print("\n");
 
-        matrix_timer = timer_now;
-        matrix_scan_count = 0;
-    }
+    matrix_timer      = timer_now;
+    matrix_scan_count = 0;
+  }
 #endif
 
 #ifdef LEFT_LEDS
-    mcp23018_status = ergodox_left_leds_update();
-#endif // LEFT_LEDS
-    for (uint8_t i = 0; i < MATRIX_ROWS_PER_SIDE; i++) {
-        select_row(i);
-        // and select on left hand
-        select_row(i + MATRIX_ROWS_PER_SIDE);
-        // we don't need a 30us delay anymore, because selecting a
-        // left-hand row requires more than 30us for i2c.
-
-        // grab cols from left hand
-        matrix[i] = debounce_read_cols(i);
-        // grab cols from right hand
-        matrix[i + MATRIX_ROWS_PER_SIDE] = debounce_read_cols(i + MATRIX_ROWS_PER_SIDE);
-
-        unselect_rows();
-    }
-
-    matrix_scan_quantum();
+  mcp23018_status = ergodox_left_leds_update();
+#endif  // LEFT_LEDS
+  for (uint8_t i = 0; i < MATRIX_ROWS_PER_SIDE; i++) {
+    // select rows from left and right hands
+    select_row(i);
+    select_row(i + MATRIX_ROWS_PER_SIDE);
+
+    // we don't need a 30us delay anymore, because selecting a
+    // left-hand row requires more than 30us for i2c.
+
+    // grab left + right cols.
+    raw_matrix[i] = read_cols(i);    
+    raw_matrix[i+MATRIX_ROWS_PER_SIDE] = read_cols(i+MATRIX_ROWS_PER_SIDE);
+    
+    unselect_rows();
+  }
+  
+  debounce(raw_matrix, matrix, MATRIX_ROWS, true);
+  matrix_scan_quantum();
 
-    return 1;
+  return 1;
 }
 
-bool matrix_is_modified(void) // deprecated and evidently not called.
+bool matrix_is_modified(void)  // deprecated and evidently not called.
 {
-    return true;
+  return true;
 }
 
-inline
-bool matrix_is_on(uint8_t row, uint8_t col)
-{
-    return (matrix[row] & ((matrix_row_t)1<<col));
-}
+inline bool matrix_is_on(uint8_t row, uint8_t col) { return (matrix[row] & ((matrix_row_t)1 << col)); }
 
-inline
-matrix_row_t matrix_get_row(uint8_t row)
-{
-    return matrix[row];
-}
+inline matrix_row_t matrix_get_row(uint8_t row) { return matrix[row]; }
 
-void matrix_print(void)
-{
-    print("\nr/c 0123456789ABCDEF\n");
-    for (uint8_t row = 0; row < MATRIX_ROWS; row++) {
-        phex(row); print(": ");
-        pbin_reverse16(matrix_get_row(row));
-        print("\n");
-    }
+void matrix_print(void) {
+  print("\nr/c 0123456789ABCDEF\n");
+  for (uint8_t row = 0; row < MATRIX_ROWS; row++) {
+    phex(row);
+    print(": ");
+    pbin_reverse16(matrix_get_row(row));
+    print("\n");
+  }
 }
 
-uint8_t matrix_key_count(void)
-{
-    uint8_t count = 0;
-    for (uint8_t i = 0; i < MATRIX_ROWS; i++) {
-        count += bitpop16(matrix[i]);
-    }
-    return count;
+uint8_t matrix_key_count(void) {
+  uint8_t count = 0;
+  for (uint8_t i = 0; i < MATRIX_ROWS; i++) {
+    count += bitpop16(matrix[i]);
+  }
+  return count;
 }
 
 /* Column pin configuration
@@ -284,43 +215,45 @@ uint8_t matrix_key_count(void)
  * col: 0   1   2   3   4   5
  * pin: B5  B4  B3  B2  B1  B0
  */
-static void  init_cols(void)
-{
-    // init on mcp23018
-    // not needed, already done as part of init_mcp23018()
-
-    // init on teensy
-    // Input with pull-up(DDR:0, PORT:1)
-    DDRF  &= ~(1<<7 | 1<<6 | 1<<5 | 1<<4 | 1<<1 | 1<<0);
-    PORTF |=  (1<<7 | 1<<6 | 1<<5 | 1<<4 | 1<<1 | 1<<0);
+static void init_cols(void) {
+  // init on mcp23018
+  // not needed, already done as part of init_mcp23018()
+
+  // init on teensy
+  // Input with pull-up(DDR:0, PORT:1)
+  DDRF &= ~(1 << 7 | 1 << 6 | 1 << 5 | 1 << 4 | 1 << 1 | 1 << 0);
+  PORTF |= (1 << 7 | 1 << 6 | 1 << 5 | 1 << 4 | 1 << 1 | 1 << 0);
 }
 
-static matrix_row_t read_cols(uint8_t row)
-{
-    if (row < 7) {
-        if (mcp23018_status) { // if there was an error
-            return 0;
-        } else {
-            uint8_t data = 0;
-            mcp23018_status = i2c_start(I2C_ADDR_WRITE, ERGODOX_EZ_I2C_TIMEOUT);    if (mcp23018_status) goto out;
-            mcp23018_status = i2c_write(GPIOB, ERGODOX_EZ_I2C_TIMEOUT);             if (mcp23018_status) goto out;
-            mcp23018_status = i2c_start(I2C_ADDR_READ, ERGODOX_EZ_I2C_TIMEOUT);     if (mcp23018_status) goto out;
-            mcp23018_status = i2c_read_nack(ERGODOX_EZ_I2C_TIMEOUT);                if (mcp23018_status < 0) goto out;
-            data = ~((uint8_t)mcp23018_status);
-            mcp23018_status = I2C_STATUS_SUCCESS;
-        out:
-            i2c_stop();
-            return data;
-        }
+static matrix_row_t read_cols(uint8_t row) {
+  if (row < 7) {
+    if (mcp23018_status) {  // if there was an error
+      return 0;
     } else {
-        /* read from teensy
-         * bitmask is 0b11110011, but we want those all
-         * in the lower six bits.
-         * we'll return 1s for the top two, but that's harmless.
-         */
-
-        return ~((PINF & 0x03) | ((PINF & 0xF0) >> 2));
+      uint8_t data    = 0;
+      mcp23018_status = i2c_start(I2C_ADDR_WRITE, ERGODOX_EZ_I2C_TIMEOUT);
+      if (mcp23018_status) goto out;
+      mcp23018_status = i2c_write(GPIOB, ERGODOX_EZ_I2C_TIMEOUT);
+      if (mcp23018_status) goto out;
+      mcp23018_status = i2c_start(I2C_ADDR_READ, ERGODOX_EZ_I2C_TIMEOUT);
+      if (mcp23018_status) goto out;
+      mcp23018_status = i2c_read_nack(ERGODOX_EZ_I2C_TIMEOUT);
+      if (mcp23018_status < 0) goto out;
+      data            = ~((uint8_t)mcp23018_status);
+      mcp23018_status = I2C_STATUS_SUCCESS;
+    out:
+      i2c_stop();
+      return data;
     }
+  } else {
+    /* read from teensy
+     * bitmask is 0b11110011, but we want those all
+     * in the lower six bits.
+     * we'll return 1s for the top two, but that's harmless.
+     */
+
+    return ~((PINF & 0x03) | ((PINF & 0xF0) >> 2));
+  }
 }
 
 /* Row pin configuration
@@ -333,69 +266,70 @@ static matrix_row_t read_cols(uint8_t row)
  * row: 0   1   2   3   4   5   6
  * pin: A0  A1  A2  A3  A4  A5  A6
  */
-static void unselect_rows(void)
-{
-    // no need to unselect on mcp23018, because the select step sets all
-    // the other row bits high, and it's not changing to a different
-    // direction
-
-    // unselect on teensy
-    // Hi-Z(DDR:0, PORT:0) to unselect
-    DDRB  &= ~(1<<0 | 1<<1 | 1<<2 | 1<<3);
-    PORTB &= ~(1<<0 | 1<<1 | 1<<2 | 1<<3);
-    DDRD  &= ~(1<<2 | 1<<3);
-    PORTD &= ~(1<<2 | 1<<3);
-    DDRC  &= ~(1<<6);
-    PORTC &= ~(1<<6);
+static void unselect_rows(void) {
+  // no need to unselect on mcp23018, because the select step sets all
+  // the other row bits high, and it's not changing to a different
+  // direction
+
+  // unselect on teensy
+  // Hi-Z(DDR:0, PORT:0) to unselect
+  DDRB &= ~(1 << 0 | 1 << 1 | 1 << 2 | 1 << 3);
+  PORTB &= ~(1 << 0 | 1 << 1 | 1 << 2 | 1 << 3);
+  DDRD &= ~(1 << 2 | 1 << 3);
+  PORTD &= ~(1 << 2 | 1 << 3);
+  DDRC &= ~(1 << 6);
+  PORTC &= ~(1 << 6);
 }
 
-static void select_row(uint8_t row)
-{
-    if (row < 7) {
-        // select on mcp23018
-        if (mcp23018_status) { // if there was an error
-            // do nothing
-        } else {
-            // set active row low  : 0
-            // set other rows hi-Z : 1
-            mcp23018_status = i2c_start(I2C_ADDR_WRITE, ERGODOX_EZ_I2C_TIMEOUT);        if (mcp23018_status) goto out;
-            mcp23018_status = i2c_write(GPIOA, ERGODOX_EZ_I2C_TIMEOUT);                 if (mcp23018_status) goto out;
-            mcp23018_status = i2c_write(0xFF & ~(1<<row), ERGODOX_EZ_I2C_TIMEOUT);      if (mcp23018_status) goto out;
-        out:
-            i2c_stop();
-        }
+static void select_row(uint8_t row) {
+  if (row < 7) {
+    // select on mcp23018
+    if (mcp23018_status) {  // if there was an error
+                            // do nothing
     } else {
-        // select on teensy
-        // Output low(DDR:1, PORT:0) to select
-        switch (row) {
-            case 7:
-                DDRB  |= (1<<0);
-                PORTB &= ~(1<<0);
-                break;
-            case 8:
-                DDRB  |= (1<<1);
-                PORTB &= ~(1<<1);
-                break;
-            case 9:
-                DDRB  |= (1<<2);
-                PORTB &= ~(1<<2);
-                break;
-            case 10:
-                DDRB  |= (1<<3);
-                PORTB &= ~(1<<3);
-                break;
-            case 11:
-                DDRD  |= (1<<2);
-                PORTD &= ~(1<<2);
-                break;
-            case 12:
-                DDRD  |= (1<<3);
-                PORTD &= ~(1<<3);
-                break;
-            case 13:
-                DDRC  |= (1<<6);
-                PORTC &= ~(1<<6);
-                break;
-        }
+      // set active row low  : 0
+      // set other rows hi-Z : 1
+      mcp23018_status = i2c_start(I2C_ADDR_WRITE, ERGODOX_EZ_I2C_TIMEOUT);
+      if (mcp23018_status) goto out;
+      mcp23018_status = i2c_write(GPIOA, ERGODOX_EZ_I2C_TIMEOUT);
+      if (mcp23018_status) goto out;
+      mcp23018_status = i2c_write(0xFF & ~(1 << row), ERGODOX_EZ_I2C_TIMEOUT);
+      if (mcp23018_status) goto out;
+    out:
+      i2c_stop();
+    }
+  } else {
+    // select on teensy
+    // Output low(DDR:1, PORT:0) to select
+    switch (row) {
+      case 7:
+        DDRB |= (1 << 0);
+        PORTB &= ~(1 << 0);
+        break;
+      case 8:
+        DDRB |= (1 << 1);
+        PORTB &= ~(1 << 1);
+        break;
+      case 9:
+        DDRB |= (1 << 2);
+        PORTB &= ~(1 << 2);
+        break;
+      case 10:
+        DDRB |= (1 << 3);
+        PORTB &= ~(1 << 3);
+        break;
+      case 11:
+        DDRD |= (1 << 2);
+        PORTD &= ~(1 << 2);
+        break;
+      case 12:
+        DDRD |= (1 << 3);
+        PORTD &= ~(1 << 3);
+        break;
+      case 13:
+        DDRC |= (1 << 6);
+        PORTC &= ~(1 << 6);
+        break;
     }
+  }
 }
diff --git a/keyboards/ergodox_ez/rules.mk b/keyboards/ergodox_ez/rules.mk
index 446ba3e21..e96cd2082 100644
--- a/keyboards/ergodox_ez/rules.mk
+++ b/keyboards/ergodox_ez/rules.mk
@@ -83,6 +83,7 @@ SLEEP_LED_ENABLE = no
 API_SYSEX_ENABLE = no
 RGBLIGHT_ENABLE = yes
 RGB_MATRIX_ENABLE = no # enable later
+DEBOUNCE_TYPE = eager_pr
 
 ifeq ($(strip $(RGB_MATRIX_ENABLE)), no)
   SRC += i2c_master.c
diff --git a/quantum/debounce/eager_pr.c b/quantum/debounce/eager_pr.c
new file mode 100644
index 000000000..9eb9480a7
--- /dev/null
+++ b/quantum/debounce/eager_pr.c
@@ -0,0 +1,100 @@
+/*
+Copyright 2019 Alex Ong<the.onga@gmail.com>
+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/>.
+*/
+
+/*
+Basic per-row algorithm. Uses an 8-bit counter per row.
+After pressing a key, it immediately changes state, and sets a counter.
+No further inputs are accepted until DEBOUNCE milliseconds have occurred.
+*/
+
+#include "matrix.h"
+#include "timer.h"
+#include "quantum.h"
+#include <stdlib.h>
+
+#ifndef DEBOUNCE
+  #define DEBOUNCE 5
+#endif
+
+
+#define debounce_counter_t uint8_t
+
+static debounce_counter_t *debounce_counters;
+
+#define DEBOUNCE_ELAPSED 251
+#define MAX_DEBOUNCE (DEBOUNCE_ELAPSED - 1)
+
+void update_debounce_counters(uint8_t num_rows, uint8_t current_time);
+void transfer_matrix_values(matrix_row_t raw[], matrix_row_t cooked[], uint8_t num_rows, uint8_t current_time);
+
+//we use num_rows rather than MATRIX_ROWS to support split keyboards
+void debounce_init(uint8_t num_rows)
+{
+  debounce_counters = (debounce_counter_t*)malloc(num_rows*sizeof(debounce_counter_t));  
+  for (uint8_t r = 0; r < num_rows; r++)
+  {    
+    debounce_counters[r] = DEBOUNCE_ELAPSED;
+  }
+}
+
+void debounce(matrix_row_t raw[], matrix_row_t cooked[], uint8_t num_rows, bool changed)
+{
+  uint8_t current_time = timer_read() % MAX_DEBOUNCE;
+  update_debounce_counters(num_rows, current_time);
+  transfer_matrix_values(raw, cooked, num_rows, current_time);
+}
+
+//If the current time is > debounce counter, set the counter to enable input.
+void update_debounce_counters(uint8_t num_rows, uint8_t current_time)
+{
+  debounce_counter_t *debounce_pointer = debounce_counters;
+  for (uint8_t row = 0; row < num_rows; row++)
+  {    
+    if (*debounce_pointer != DEBOUNCE_ELAPSED)
+    {
+      if (TIMER_DIFF(current_time, *debounce_pointer, MAX_DEBOUNCE) >= DEBOUNCE) {
+        *debounce_pointer = DEBOUNCE_ELAPSED;
+      }
+    }
+    debounce_pointer++;
+  }
+}
+
+// upload from raw_matrix to final matrix;
+void transfer_matrix_values(matrix_row_t raw[], matrix_row_t cooked[], uint8_t num_rows, uint8_t current_time)
+{
+  debounce_counter_t *debounce_pointer = debounce_counters;
+  for (uint8_t row = 0; row < num_rows; row++)
+  {
+    matrix_row_t existing_row = cooked[row]; 
+    matrix_row_t raw_row = raw[row];
+    
+    //determine new value basd on debounce pointer + raw value
+    if (*debounce_pointer == DEBOUNCE_ELAPSED &&
+      (existing_row != raw_row))
+    {
+      *debounce_pointer = current_time;
+      existing_row = raw_row; 
+    }
+    cooked[row] = existing_row;
+    
+    debounce_pointer++;
+  }  
+}
+
+bool debounce_active(void)
+{
+  return true;
+}
+
diff --git a/quantum/debounce/readme.md b/quantum/debounce/readme.md
index 5b318d845..f77f78c76 100644
--- a/quantum/debounce/readme.md
+++ b/quantum/debounce/readme.md
@@ -22,7 +22,7 @@ Here are a few that could be implemented:
 sym_g.c
 sym_pk.c
 sym_pr.c
-sym_pr_cycles.c //currently used in ergo-dox
+sym_pr_cycles.c 
 eager_g.c
 eager_pk.c
 eager_pr.c //could be used in ergo-dox!