Changes lets_split to use timer based debouncing

The let's split code used delays in its debouncing algorithm which
increases input latency. This commit copies and adapts the code from
`quantum/matrix.c` to lets_split's `matrix.c`.

2 files changed, 197 insertions, 47 deletions

diff --git a/keyboards/lets_split/matrix.c b/keyboards/lets_split/matrix.c
index 81dfb14455..4def27239c 100644
--- a/keyboards/lets_split/matrix.c
+++ b/keyboards/lets_split/matrix.c
@@ -21,9 +21,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <stdint.h>
 #include <stdbool.h>
 #include <avr/io.h>
-#include <avr/wdt.h>
-#include <avr/interrupt.h>
-#include <util/delay.h>
+#include "wait.h"
 #include "print.h"
 #include "debug.h"
 #include "util.h"
@@ -31,6 +29,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "split_util.h"
 #include "pro_micro.h"
 #include "config.h"
+#include "timer.h"
 
 #ifdef USE_I2C
 #  include "i2c.h"
@@ -38,14 +37,29 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #  include "serial.h"
 #endif
 
-#ifndef DEBOUNCE
-#  define DEBOUNCE	5
+#ifndef DEBOUNCING_DELAY
+#   define DEBOUNCING_DELAY 5
 #endif
 
+#if (DEBOUNCING_DELAY > 0)
+    static uint16_t debouncing_time;
+    static bool debouncing = false;
+#endif
+
+#if (MATRIX_COLS <= 8)
+#    define print_matrix_header()  print("\nr/c 01234567\n")
+#    define print_matrix_row(row)  print_bin_reverse8(matrix_get_row(row))
+#    define matrix_bitpop(i)       bitpop(matrix[i])
+#    define ROW_SHIFTER ((uint8_t)1)
+#else
+#    error "Currently only supports 8 COLS"
+#endif
+static matrix_row_t matrix_debouncing[MATRIX_ROWS];
+
 #define ERROR_DISCONNECT_COUNT 5
 
-static uint8_t debouncing = DEBOUNCE;
-static const int ROWS_PER_HAND = MATRIX_ROWS/2;
+#define ROWS_PER_HAND (MATRIX_ROWS/2)
+
 static uint8_t error_count = 0;
 
 static const uint8_t row_pins[MATRIX_ROWS] = MATRIX_ROW_PINS;
@@ -55,11 +69,19 @@ static const uint8_t col_pins[MATRIX_COLS] = MATRIX_COL_PINS;
 static matrix_row_t matrix[MATRIX_ROWS];
 static matrix_row_t matrix_debouncing[MATRIX_ROWS];
 
-static matrix_row_t read_cols(void);
-static void init_cols(void);
-static void unselect_rows(void);
-static void select_row(uint8_t row);
-
+#if (DIODE_DIRECTION == COL2ROW)
+    static void init_cols(void);
+    static bool read_cols_on_row(matrix_row_t current_matrix[], uint8_t current_row);
+    static void unselect_rows(void);
+    static void select_row(uint8_t row);
+    static void unselect_row(uint8_t row);
+#elif (DIODE_DIRECTION == ROW2COL)
+    static void init_rows(void);
+    static bool read_rows_on_col(matrix_row_t current_matrix[], uint8_t current_col);
+    static void unselect_cols(void);
+    static void unselect_col(uint8_t col);
+    static void select_col(uint8_t col);
+#endif
 __attribute__ ((weak))
 void matrix_init_quantum(void) {
     matrix_init_kb();
@@ -118,33 +140,54 @@ void matrix_init(void)
     }
 
     matrix_init_quantum();
+
 }
 
 uint8_t _matrix_scan(void)
 {
-    // Right hand is stored after the left in the matirx so, we need to offset it
     int offset = isLeftHand ? 0 : (ROWS_PER_HAND);
+#if (DIODE_DIRECTION == COL2ROW)
+    // Set row, read cols
+    for (uint8_t current_row = 0; current_row < ROWS_PER_HAND; current_row++) {
+#       if (DEBOUNCING_DELAY > 0)
+            bool matrix_changed = read_cols_on_row(matrix_debouncing+offset, current_row);
+
+            if (matrix_changed) {
+                debouncing = true;
+                debouncing_time = timer_read();
+                PORTD ^= (1 << 2);
+            }
+
+#       else
+            read_cols_on_row(matrix+offset, current_row);
+#       endif
+
+    }
+
+#elif (DIODE_DIRECTION == ROW2COL)
+    // Set col, read rows
+    for (uint8_t current_col = 0; current_col < MATRIX_COLS; current_col++) {
+#       if (DEBOUNCING_DELAY > 0)
+            bool matrix_changed = read_rows_on_col(matrix_debouncing+offset, current_col);
+            if (matrix_changed) {
+                debouncing = true;
+                debouncing_time = timer_read();
+            }
+#       else
+             read_rows_on_col(matrix+offset, current_col);
+#       endif
 
-    for (uint8_t i = 0; i < ROWS_PER_HAND; i++) {
-        select_row(i);
-        _delay_us(30);  // without this wait read unstable value.
-        matrix_row_t cols = read_cols();
-        if (matrix_debouncing[i+offset] != cols) {
-            matrix_debouncing[i+offset] = cols;
-            debouncing = DEBOUNCE;
-        }
-        unselect_rows();
     }
+#endif
 
-    if (debouncing) {
-        if (--debouncing) {
-            _delay_ms(1);
-        } else {
+#   if (DEBOUNCING_DELAY > 0)
+        if (debouncing && (timer_elapsed(debouncing_time) > DEBOUNCING_DELAY)) {
             for (uint8_t i = 0; i < ROWS_PER_HAND; i++) {
                 matrix[i+offset] = matrix_debouncing[i+offset];
             }
+            debouncing = false;
         }
-    }
+#   endif
 
     return 1;
 }
@@ -200,9 +243,7 @@ int serial_transaction(void) {
 
 uint8_t matrix_scan(void)
 {
-    int ret = _matrix_scan();
-
-
+    uint8_t ret = _matrix_scan();
 
 #ifdef USE_I2C
     if( i2c_transaction() ) {
@@ -233,11 +274,10 @@ uint8_t matrix_scan(void)
 void matrix_slave_scan(void) {
     _matrix_scan();
 
-    int offset = (isLeftHand) ? 0 : (MATRIX_ROWS / 2);
+    int offset = (isLeftHand) ? 0 : ROWS_PER_HAND;
 
 #ifdef USE_I2C
     for (int i = 0; i < ROWS_PER_HAND; ++i) {
-        /* i2c_slave_buffer[i] = matrix[offset+i]; */
         i2c_slave_buffer[i] = matrix[offset+i];
     }
 #else // USE_SERIAL
@@ -284,33 +324,141 @@ uint8_t matrix_key_count(void)
     return count;
 }
 
-static void  init_cols(void)
+#if (DIODE_DIRECTION == COL2ROW)
+
+static void init_cols(void)
 {
-    for(int x = 0; x < MATRIX_COLS; x++) {
-        _SFR_IO8((col_pins[x] >> 4) + 1) &=  ~_BV(col_pins[x] & 0xF);
-        _SFR_IO8((col_pins[x] >> 4) + 2) |= _BV(col_pins[x] & 0xF);
+    for(uint8_t x = 0; x < MATRIX_COLS; x++) {
+        uint8_t pin = col_pins[x];
+        _SFR_IO8((pin >> 4) + 1) &= ~_BV(pin & 0xF); // IN
+        _SFR_IO8((pin >> 4) + 2) |=  _BV(pin & 0xF); // HI
     }
 }
 
-static matrix_row_t read_cols(void)
+static bool read_cols_on_row(matrix_row_t current_matrix[], uint8_t current_row)
 {
-    matrix_row_t result = 0;
-    for(int x = 0; x < MATRIX_COLS; x++) {
-        result |= (_SFR_IO8(col_pins[x] >> 4) & _BV(col_pins[x] & 0xF)) ? 0 : (1 << x);
+    // Store last value of row prior to reading
+    matrix_row_t last_row_value = current_matrix[current_row];
+
+    // Clear data in matrix row
+    current_matrix[current_row] = 0;
+
+    // Select row and wait for row selecton to stabilize
+    select_row(current_row);
+    wait_us(30);
+
+    // For each col...
+    for(uint8_t col_index = 0; col_index < MATRIX_COLS; col_index++) {
+
+        // Select the col pin to read (active low)
+        uint8_t pin = col_pins[col_index];
+        uint8_t pin_state = (_SFR_IO8(pin >> 4) & _BV(pin & 0xF));
+
+        // Populate the matrix row with the state of the col pin
+        current_matrix[current_row] |=  pin_state ? 0 : (ROW_SHIFTER << col_index);
     }
-    return result;
+
+    // Unselect row
+    unselect_row(current_row);
+
+    return (last_row_value != current_matrix[current_row]);
+}
+
+static void select_row(uint8_t row)
+{
+    uint8_t pin = row_pins[row];
+    _SFR_IO8((pin >> 4) + 1) |=  _BV(pin & 0xF); // OUT
+    _SFR_IO8((pin >> 4) + 2) &= ~_BV(pin & 0xF); // LOW
+}
+
+static void unselect_row(uint8_t row)
+{
+    uint8_t pin = row_pins[row];
+    _SFR_IO8((pin >> 4) + 1) &= ~_BV(pin & 0xF); // IN
+    _SFR_IO8((pin >> 4) + 2) |=  _BV(pin & 0xF); // HI
 }
 
 static void unselect_rows(void)
 {
-    for(int x = 0; x < ROWS_PER_HAND; x++) {
-        _SFR_IO8((row_pins[x] >> 4) + 1) &=  ~_BV(row_pins[x] & 0xF);
-        _SFR_IO8((row_pins[x] >> 4) + 2) |= _BV(row_pins[x] & 0xF);
+    for(uint8_t x = 0; x < ROWS_PER_HAND; x++) {
+        uint8_t pin = row_pins[x];
+        _SFR_IO8((pin >> 4) + 1) &= ~_BV(pin & 0xF); // IN
+        _SFR_IO8((pin >> 4) + 2) |=  _BV(pin & 0xF); // HI
     }
 }
 
-static void select_row(uint8_t row)
+#elif (DIODE_DIRECTION == ROW2COL)
+
+static void init_rows(void)
+{
+    for(uint8_t x = 0; x < ROWS_PER_HAND; x++) {
+        uint8_t pin = row_pins[x];
+        _SFR_IO8((pin >> 4) + 1) &= ~_BV(pin & 0xF); // IN
+        _SFR_IO8((pin >> 4) + 2) |=  _BV(pin & 0xF); // HI
+    }
+}
+
+static bool read_rows_on_col(matrix_row_t current_matrix[], uint8_t current_col)
+{
+    bool matrix_changed = false;
+
+    // Select col and wait for col selecton to stabilize
+    select_col(current_col);
+    wait_us(30);
+
+    // For each row...
+    for(uint8_t row_index = 0; row_index < ROWS_PER_HAND; row_index++)
+    {
+
+        // Store last value of row prior to reading
+        matrix_row_t last_row_value = current_matrix[row_index];
+
+        // Check row pin state
+        if ((_SFR_IO8(row_pins[row_index] >> 4) & _BV(row_pins[row_index] & 0xF)) == 0)
+        {
+            // Pin LO, set col bit
+            current_matrix[row_index] |= (ROW_SHIFTER << current_col);
+        }
+        else
+        {
+            // Pin HI, clear col bit
+            current_matrix[row_index] &= ~(ROW_SHIFTER << current_col);
+        }
+
+        // Determine if the matrix changed state
+        if ((last_row_value != current_matrix[row_index]) && !(matrix_changed))
+        {
+            matrix_changed = true;
+        }
+    }
+
+    // Unselect col
+    unselect_col(current_col);
+
+    return matrix_changed;
+}
+
+static void select_col(uint8_t col)
+{
+    uint8_t pin = col_pins[col];
+    _SFR_IO8((pin >> 4) + 1) |=  _BV(pin & 0xF); // OUT
+    _SFR_IO8((pin >> 4) + 2) &= ~_BV(pin & 0xF); // LOW
+}
+
+static void unselect_col(uint8_t col)
+{
+    uint8_t pin = col_pins[col];
+    _SFR_IO8((pin >> 4) + 1) &= ~_BV(pin & 0xF); // IN
+    _SFR_IO8((pin >> 4) + 2) |=  _BV(pin & 0xF); // HI
+}
+
+static void unselect_cols(void)
 {
-    _SFR_IO8((row_pins[row] >> 4) + 1) |=  _BV(row_pins[row] & 0xF);
-    _SFR_IO8((row_pins[row] >> 4) + 2) &= ~_BV(row_pins[row] & 0xF);
+    for(uint8_t x = 0; x < MATRIX_COLS; x++) {
+        uint8_t pin = col_pins[x];
+        _SFR_IO8((pin >> 4) + 1) &= ~_BV(pin & 0xF); // IN
+        _SFR_IO8((pin >> 4) + 2) |=  _BV(pin & 0xF); // HI
+    }
 }
+
+#endif
diff --git a/keyboards/lets_split/split_util.c b/keyboards/lets_split/split_util.c
index 39639c3b4b..346cbc9089 100644
--- a/keyboards/lets_split/split_util.c
+++ b/keyboards/lets_split/split_util.c
@@ -8,6 +8,7 @@
 #include "matrix.h"
 #include "keyboard.h"
 #include "config.h"
+#include "timer.h"
 
 #ifdef USE_I2C
 #  include "i2c.h"
@@ -42,6 +43,7 @@ static void keyboard_master_setup(void) {
 }
 
 static void keyboard_slave_setup(void) {
+  timer_init();
 #ifdef USE_I2C
     i2c_slave_init(SLAVE_I2C_ADDRESS);
 #else