20 files changed, 255 insertions, 293 deletions

diff --git a/tmk_core/common/action.c b/tmk_core/common/action.c
index b99c2acaa7..ec8d6ed7b9 100644
--- a/tmk_core/common/action.c
+++ b/tmk_core/common/action.c
@@ -653,7 +653,7 @@ void process_action(keyrecord_t *record, action_t action)
 
 #ifndef NO_ACTION_TAPPING
   #ifdef RETRO_TAPPING
-  if (!is_tap_key(record->event.key)) {
+  if (!is_tap_action(action)) {
     retro_tapping_counter = 0;
   } else {
     if (event.pressed) {
@@ -929,7 +929,15 @@ void clear_keyboard_but_mods_and_keys()
 bool is_tap_key(keypos_t key)
 {
     action_t action = layer_switch_get_action(key);
+    return is_tap_action(action);
+}
 
+/** \brief Utilities for actions. (FIXME: Needs better description)
+ *
+ * FIXME: Needs documentation.
+ */
+bool is_tap_action(action_t action)
+{
     switch (action.kind.id) {
         case ACT_LMODS_TAP:
         case ACT_RMODS_TAP:
diff --git a/tmk_core/common/action.h b/tmk_core/common/action.h
index 8e47e5339e..799e3bb0ef 100644
--- a/tmk_core/common/action.h
+++ b/tmk_core/common/action.h
@@ -97,6 +97,7 @@ void clear_keyboard_but_mods(void);
 void clear_keyboard_but_mods_and_keys(void);
 void layer_switch(uint8_t new_layer);
 bool is_tap_key(keypos_t key);
+bool is_tap_action(action_t action);
 
 #ifndef NO_ACTION_TAPPING
 void process_record_tap_hint(keyrecord_t *record);
diff --git a/tmk_core/common/action_layer.c b/tmk_core/common/action_layer.c
index 120ce3f51b..6ff8c5549b 100644
--- a/tmk_core/common/action_layer.c
+++ b/tmk_core/common/action_layer.c
@@ -17,82 +17,76 @@ uint32_t default_layer_state = 0;
 
 /** \brief Default Layer State Set At user Level
  *
- * FIXME: Needs docs
+ * Run user code on default layer state change
  */
 __attribute__((weak))
 uint32_t default_layer_state_set_user(uint32_t state) {
-    return state;
+  return state;
 }
 
 /** \brief Default Layer State Set At Keyboard Level
  *
- * FIXME: Needs docs
+ *  Run keyboard code on default layer state change
  */
 __attribute__((weak))
 uint32_t default_layer_state_set_kb(uint32_t state) {
-    return default_layer_state_set_user(state);
+  return default_layer_state_set_user(state);
 }
 
 /** \brief Default Layer State Set
  *
- * FIXME: Needs docs
+ * Static function to set the default layer state, prints debug info and clears keys
  */
-static void default_layer_state_set(uint32_t state)
-{
-    state = default_layer_state_set_kb(state);
-    debug("default_layer_state: ");
-    default_layer_debug(); debug(" to ");
-    default_layer_state = state;
-    default_layer_debug(); debug("\n");
+static void default_layer_state_set(uint32_t state) {
+  state = default_layer_state_set_kb(state);
+  debug("default_layer_state: ");
+  default_layer_debug(); debug(" to ");
+  default_layer_state = state;
+  default_layer_debug(); debug("\n");
 #ifdef STRICT_LAYER_RELEASE
-    clear_keyboard_but_mods(); // To avoid stuck keys
+  clear_keyboard_but_mods(); // To avoid stuck keys
 #else
-    clear_keyboard_but_mods_and_keys(); // Don't reset held keys
+  clear_keyboard_but_mods_and_keys(); // Don't reset held keys
 #endif
 }
 
 /** \brief Default Layer Print
  *
- * FIXME: Needs docs
+ * Print out the hex value of the 32-bit default layer state, as well as the value of the highest bit.
  */
-void default_layer_debug(void)
-{
-    dprintf("%08lX(%u)", default_layer_state, biton32(default_layer_state));
+void default_layer_debug(void) {
+  dprintf("%08lX(%u)", default_layer_state, biton32(default_layer_state));
 }
 
 /** \brief Default Layer Set
  *
- * FIXME: Needs docs
+ * Sets the default layer state.
  */
-void default_layer_set(uint32_t state)
-{
-    default_layer_state_set(state);
+void default_layer_set(uint32_t state) {
+  default_layer_state_set(state);
 }
 
 #ifndef NO_ACTION_LAYER
 /** \brief Default Layer Or
  *
- * FIXME: Needs docs
+ * Turns on the default layer based on matching bits between specifed layer and existing layer state
  */
-void default_layer_or(uint32_t state)
-{
-    default_layer_state_set(default_layer_state | state);
+void default_layer_or(uint32_t state) {
+  default_layer_state_set(default_layer_state | state);
 }
 /** \brief Default Layer And
  *
- * FIXME: Needs docs
+ * Turns on default layer based on matching enabled bits between specifed layer and existing layer state
  */
-void default_layer_and(uint32_t state)
-{
-    default_layer_state_set(default_layer_state & state);
+void default_layer_and(uint32_t state) {
+  default_layer_state_set(default_layer_state & state);
 }
 /** \brief Default Layer Xor
  *
- * FIXME: Needs docs
+ * Turns on default layer based on non-matching bits between specifed layer and existing layer state
  */
-void default_layer_xor(uint32_t state)
-{
-    default_layer_state_set(default_layer_state ^ state);
+void default_layer_xor(uint32_t state) {
+  default_layer_state_set(default_layer_state ^ state);
 }
 #endif
 
@@ -104,170 +98,168 @@ uint32_t layer_state = 0;
 
 /** \brief Layer state set user
  *
- * FIXME: Needs docs
+ * Runs user code on layer state change
  */
 __attribute__((weak))
 uint32_t layer_state_set_user(uint32_t state) {
-    return state;
+  return state;
 }
 
 /** \brief Layer state set keyboard
  *
- * FIXME: Needs docs
+ * Runs keyboard code on layer state change
  */
 __attribute__((weak))
 uint32_t layer_state_set_kb(uint32_t state) {
-    return layer_state_set_user(state);
+  return layer_state_set_user(state);
 }
 
 /** \brief Layer state set
  *
- * FIXME: Needs docs
+ * Sets the layer to match the specifed state (a bitmask)
  */
-void layer_state_set(uint32_t state)
-{
-    state = layer_state_set_kb(state);
-    dprint("layer_state: ");
-    layer_debug(); dprint(" to ");
-    layer_state = state;
-    layer_debug(); dprintln();
+void layer_state_set(uint32_t state) {
+  state = layer_state_set_kb(state);
+  dprint("layer_state: ");
+  layer_debug(); dprint(" to ");
+  layer_state = state;
+  layer_debug(); dprintln();
 #ifdef STRICT_LAYER_RELEASE
-    clear_keyboard_but_mods(); // To avoid stuck keys
+  clear_keyboard_but_mods(); // To avoid stuck keys
 #else
-    clear_keyboard_but_mods_and_keys(); // Don't reset held keys
+  clear_keyboard_but_mods_and_keys(); // Don't reset held keys
 #endif
 }
 
 /** \brief Layer clear
  *
- * FIXME: Needs docs
+ * Turn off all layers
  */
-void layer_clear(void)
-{
-    layer_state_set(0);
+void layer_clear(void) {
+  layer_state_set(0);
 }
 
 /** \brief Layer state is
  *
- * FIXME: Needs docs
+ * Return whether the given state is on (it might still be shadowed by a higher state, though)
  */
-bool layer_state_is(uint8_t layer)
-{
-    return layer_state_cmp(layer_state, layer);
+bool layer_state_is(uint8_t layer) {
+  return layer_state_cmp(layer_state, layer);
 }
 
 /** \brief Layer state compare
  *
- * FIXME: Needs docs
+ * Used for comparing layers {mostly used for unit testing}
  */
 bool layer_state_cmp(uint32_t cmp_layer_state, uint8_t layer) {
-    if (!cmp_layer_state) { return layer == 0; }
-    return (cmp_layer_state & (1UL<<layer)) != 0;
+  if (!cmp_layer_state) { return layer == 0; }
+  return (cmp_layer_state & (1UL<<layer)) != 0;
 }
 
 /** \brief Layer move
  *
- * FIXME: Needs docs
+ * Turns on the given layer and turn off all other layers
  */
-void layer_move(uint8_t layer)
-{
-    layer_state_set(1UL<<layer);
+void layer_move(uint8_t layer) {
+  layer_state_set(1UL<<layer);
 }
 
 /** \brief Layer on
  *
- * FIXME: Needs docs
+ * Turns on given layer
  */
-void layer_on(uint8_t layer)
-{
-    layer_state_set(layer_state | (1UL<<layer));
+void layer_on(uint8_t layer) {
+  layer_state_set(layer_state | (1UL<<layer));
 }
 
 /** \brief Layer off
  *
- * FIXME: Needs docs
+ * Turns off given layer
  */
-void layer_off(uint8_t layer)
-{
-    layer_state_set(layer_state & ~(1UL<<layer));
+void layer_off(uint8_t layer) {
+  layer_state_set(layer_state & ~(1UL<<layer));
 }
 
 /** \brief Layer invert
  *
- * FIXME: Needs docs
+ * Toggle the given layer (set it if it's unset, or unset it if it's set)
  */
-void layer_invert(uint8_t layer)
-{
-    layer_state_set(layer_state ^ (1UL<<layer));
+void layer_invert(uint8_t layer) {
+  layer_state_set(layer_state ^ (1UL<<layer));
 }
 
 /** \brief Layer or
  *
- * FIXME: Needs docs
+ * Turns on layers based on matching bits between specifed layer and existing layer state
  */
-void layer_or(uint32_t state)
-{
-    layer_state_set(layer_state | state);
+void layer_or(uint32_t state) {
+  layer_state_set(layer_state | state);
 }
 /** \brief Layer and
  *
- * FIXME: Needs docs
+ * Turns on layers based on matching enabled bits between specifed layer and existing layer state
  */
-void layer_and(uint32_t state)
-{
-    layer_state_set(layer_state & state);
+void layer_and(uint32_t state) {
+  layer_state_set(layer_state & state);
 }
 /** \brief Layer xor
  *
- * FIXME: Needs docs
+ * Turns on layers based on non-matching bits between specifed layer and existing layer state
  */
-void layer_xor(uint32_t state)
-{
-    layer_state_set(layer_state ^ state);
+void layer_xor(uint32_t state) {
+  layer_state_set(layer_state ^ state);
 }
 
 /** \brief Layer debug printing
  *
- * FIXME: Needs docs
+ * Print out the hex value of the 32-bit layer state, as well as the value of the highest bit.
  */
-void layer_debug(void)
-{
-    dprintf("%08lX(%u)", layer_state, biton32(layer_state));
+void layer_debug(void) {
+  dprintf("%08lX(%u)", layer_state, biton32(layer_state));
 }
 #endif
 
 #if !defined(NO_ACTION_LAYER) && !defined(STRICT_LAYER_RELEASE)
+/** \brief source layer cache
+ */
+
 uint8_t source_layers_cache[(MATRIX_ROWS * MATRIX_COLS + 7) / 8][MAX_LAYER_BITS] = {{0}};
 
-void update_source_layers_cache(keypos_t key, uint8_t layer)
-{
-    const uint8_t key_number = key.col + (key.row * MATRIX_COLS);
-    const uint8_t storage_row = key_number / 8;
-    const uint8_t storage_bit = key_number % 8;
-
-    for (uint8_t bit_number = 0; bit_number < MAX_LAYER_BITS; bit_number++) {
-        source_layers_cache[storage_row][bit_number] ^=
-            (-((layer & (1U << bit_number)) != 0)
-             ^ source_layers_cache[storage_row][bit_number])
-            & (1U << storage_bit);
-    }
+/** \brief update source layers cache
+ *
+ * Updates the cached keys when changing layers
+ */
+void update_source_layers_cache(keypos_t key, uint8_t layer) {
+  const uint8_t key_number = key.col + (key.row * MATRIX_COLS);
+  const uint8_t storage_row = key_number / 8;
+  const uint8_t storage_bit = key_number % 8;
+
+  for (uint8_t bit_number = 0; bit_number < MAX_LAYER_BITS; bit_number++) {
+    source_layers_cache[storage_row][bit_number] ^=
+      (-((layer & (1U << bit_number)) != 0)
+        ^ source_layers_cache[storage_row][bit_number])
+      & (1U << storage_bit);
+  }
 }
 
-uint8_t read_source_layers_cache(keypos_t key)
-{
-    const uint8_t key_number = key.col + (key.row * MATRIX_COLS);
-    const uint8_t storage_row = key_number / 8;
-    const uint8_t storage_bit = key_number % 8;
-    uint8_t layer = 0;
-
-    for (uint8_t bit_number = 0; bit_number < MAX_LAYER_BITS; bit_number++) {
-        layer |=
-            ((source_layers_cache[storage_row][bit_number]
-              & (1U << storage_bit)) != 0)
-            << bit_number;
-    }
-
-    return layer;
+/** \brief read source layers cache
+ *
+ * reads the cached keys stored when the layer was changed
+ */
+uint8_t read_source_layers_cache(keypos_t key) {
+  const uint8_t key_number = key.col + (key.row * MATRIX_COLS);
+  const uint8_t storage_row = key_number / 8;
+  const uint8_t storage_bit = key_number % 8;
+  uint8_t layer = 0;
+
+  for (uint8_t bit_number = 0; bit_number < MAX_LAYER_BITS; bit_number++) {
+    layer |=
+      ((source_layers_cache[storage_row][bit_number]
+        & (1U << storage_bit)) != 0)
+      << bit_number;
+  }
+
+  return layer;
 }
 #endif
 
@@ -278,61 +270,58 @@ uint8_t read_source_layers_cache(keypos_t key)
  * when the layer is switched after the down event but before the up
  * event as they may get stuck otherwise.
  */
-action_t store_or_get_action(bool pressed, keypos_t key)
-{
+action_t store_or_get_action(bool pressed, keypos_t key) {
 #if !defined(NO_ACTION_LAYER) && !defined(STRICT_LAYER_RELEASE)
-    if (disable_action_cache) {
-        return layer_switch_get_action(key);
-    }
-
-    uint8_t layer;
-
-    if (pressed) {
-        layer = layer_switch_get_layer(key);
-        update_source_layers_cache(key, layer);
-    }
-    else {
-        layer = read_source_layers_cache(key);
-    }
-    return action_for_key(layer, key);
-#else
+  if (disable_action_cache) {
     return layer_switch_get_action(key);
+  }
+
+  uint8_t layer;
+
+  if (pressed) {
+    layer = layer_switch_get_layer(key);
+    update_source_layers_cache(key, layer);
+  }
+  else {
+    layer = read_source_layers_cache(key);
+  }
+  return action_for_key(layer, key);
+#else
+  return layer_switch_get_action(key);
 #endif
 }
 
 
 /** \brief Layer switch get layer
  *
- * FIXME: Needs docs
+ * Gets the layer based on key info
  */
-int8_t layer_switch_get_layer(keypos_t key)
-{
+int8_t layer_switch_get_layer(keypos_t key) {
 #ifndef NO_ACTION_LAYER
-    action_t action;
-    action.code = ACTION_TRANSPARENT;
-
-    uint32_t layers = layer_state | default_layer_state;
-    /* check top layer first */
-    for (int8_t i = 31; i >= 0; i--) {
-        if (layers & (1UL<<i)) {
-            action = action_for_key(i, key);
-            if (action.code != ACTION_TRANSPARENT) {
-                return i;
-            }
-        }
+  action_t action;
+  action.code = ACTION_TRANSPARENT;
+
+  uint32_t layers = layer_state | default_layer_state;
+  /* check top layer first */
+  for (int8_t i = 31; i >= 0; i--) {
+    if (layers & (1UL<<i)) {
+      action = action_for_key(i, key);
+      if (action.code != ACTION_TRANSPARENT) {
+          return i;
+      }
     }
-    /* fall back to layer 0 */
-    return 0;
+  }
+  /* fall back to layer 0 */
+  return 0;
 #else
-    return biton32(default_layer_state);
+  return biton32(default_layer_state);
 #endif
 }
 
 /** \brief Layer switch get layer
  *
- * FIXME: Needs docs
+ * Gets action code based on key position
  */
-action_t layer_switch_get_action(keypos_t key)
-{
-    return action_for_key(layer_switch_get_layer(key), key);
+action_t layer_switch_get_action(keypos_t key) {
+  return action_for_key(layer_switch_get_layer(key), key);
 }
diff --git a/tmk_core/common/action_util.c b/tmk_core/common/action_util.c
index afd4ae8b25..58401ace55 100644
--- a/tmk_core/common/action_util.c
+++ b/tmk_core/common/action_util.c
@@ -54,7 +54,7 @@ int8_t get_oneshot_locked_mods(void) { return oneshot_locked_mods; }
 void set_oneshot_locked_mods(int8_t mods) { oneshot_locked_mods = mods; }
 void clear_oneshot_locked_mods(void) { oneshot_locked_mods = 0; }
 #if (defined(ONESHOT_TIMEOUT) && (ONESHOT_TIMEOUT > 0))
-static int16_t oneshot_time = 0;
+static uint16_t oneshot_time = 0;
 bool has_oneshot_mods_timed_out(void) {
   return TIMER_DIFF_16(timer_read(), oneshot_time) >= ONESHOT_TIMEOUT;
 }
@@ -79,7 +79,7 @@ inline uint8_t get_oneshot_layer(void) { return oneshot_layer_data >> 3; }
 inline uint8_t get_oneshot_layer_state(void) { return oneshot_layer_data & 0b111; }
 
 #if (defined(ONESHOT_TIMEOUT) && (ONESHOT_TIMEOUT > 0))
-static int16_t oneshot_layer_time = 0;
+static uint16_t oneshot_layer_time = 0;
 inline bool has_oneshot_layer_timed_out() {
     return TIMER_DIFF_16(timer_read(), oneshot_layer_time) >= ONESHOT_TIMEOUT &&
         !(get_oneshot_layer_state() & ONESHOT_TOGGLED);
diff --git a/tmk_core/common/arm_atsam/timer.c b/tmk_core/common/arm_atsam/timer.c
index bcfe5002c3..6c3905e308 100644
--- a/tmk_core/common/arm_atsam/timer.c
+++ b/tmk_core/common/arm_atsam/timer.c
@@ -9,7 +9,7 @@ void set_time(uint64_t tset)
 
 void timer_init(void)
 {
-    ms_clk = 0;
+    timer_clear();
 }
 
 uint16_t timer_read(void)
@@ -37,23 +37,7 @@ uint32_t timer_elapsed32(uint32_t tlast)
     return TIMER_DIFF_32(timer_read32(), tlast);
 }
 
-uint32_t timer_elapsed64(uint32_t tlast)
-{
-    uint64_t tnow = timer_read64();
-    return (tnow >= tlast ? tnow - tlast : UINT64_MAX - tlast + tnow);
-}
-
 void timer_clear(void)
 {
-    ms_clk = 0;
-}
-
-void wait_ms(uint64_t msec)
-{
-    CLK_delay_ms(msec);
-}
-
-void wait_us(uint16_t usec)
-{
-    CLK_delay_us(usec);
+    set_time(0);
 }
diff --git a/tmk_core/common/host.h b/tmk_core/common/host.h
index aeabba7107..3d172eed66 100644
--- a/tmk_core/common/host.h
+++ b/tmk_core/common/host.h
@@ -15,14 +15,18 @@ You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#ifndef HOST_H
-#define HOST_H
+#pragma once
 
 #include <stdint.h>
 #include <stdbool.h>
 #include "report.h"
 #include "host_driver.h"
 
+#define IS_LED_ON(leds, led_name)   ( (leds) & (1 << (led_name)))
+#define IS_LED_OFF(leds, led_name)  (~(leds) & (1 << (led_name)))
+
+#define IS_HOST_LED_ON(led_name)    IS_LED_ON(host_keyboard_leds(), led_name)
+#define IS_HOST_LED_OFF(led_name)   IS_LED_OFF(host_keyboard_leds(), led_name)
 
 #ifdef __cplusplus
 extern "C" {
@@ -31,7 +35,6 @@ extern "C" {
 extern uint8_t keyboard_idle;
 extern uint8_t keyboard_protocol;
 
-
 /* host driver */
 void host_set_driver(host_driver_t *driver);
 host_driver_t *host_get_driver(void);
@@ -49,5 +52,3 @@ uint16_t host_last_consumer_report(void);
 #ifdef __cplusplus
 }
 #endif
-
-#endif
diff --git a/tmk_core/common/keyboard.h b/tmk_core/common/keyboard.h
index 71e594a890..ea2f336e9d 100644
--- a/tmk_core/common/keyboard.h
+++ b/tmk_core/common/keyboard.h
@@ -67,6 +67,8 @@ void keyboard_init(void);
 void keyboard_task(void);
 /* it runs when host LED status is updated */
 void keyboard_set_leds(uint8_t leds);
+/* it runs whenever code has to behave differently on a slave */
+bool is_keyboard_master(void);
 
 #ifdef __cplusplus
 }
diff --git a/tmk_core/common/keycode.h b/tmk_core/common/keycode.h
index ac3edbd215..d5904276ee 100644
--- a/tmk_core/common/keycode.h
+++ b/tmk_core/common/keycode.h
@@ -46,6 +46,22 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #define MOD_BIT(code)            (1 << MOD_INDEX(code))
 #define MOD_INDEX(code)          ((code) & 0x07)
 
+#define MOD_MASK_CTRL            (MOD_BIT(KC_LCTRL)  | MOD_BIT(KC_RCTRL))
+#define MOD_MASK_SHIFT           (MOD_BIT(KC_LSHIFT) | MOD_BIT(KC_RSHIFT))
+#define MOD_MASK_ALT             (MOD_BIT(KC_LALT)   | MOD_BIT(KC_RALT))
+#define MOD_MASK_GUI             (MOD_BIT(KC_LGUI)   | MOD_BIT(KC_RGUI))
+#define MOD_MASK_CS              (MOD_MASK_CTRL  | MOD_MASK_SHIFT)
+#define MOD_MASK_CA              (MOD_MASK_CTRL  | MOD_MASK_ALT)
+#define MOD_MASK_CG              (MOD_MASK_CTRL  | MOD_MASK_GUI)
+#define MOD_MASK_SA              (MOD_MASK_SHIFT | MOD_MASK_ALT)
+#define MOD_MASK_SG              (MOD_MASK_SHIFT | MOD_MASK_GUI)
+#define MOD_MASK_AG              (MOD_MASK_ALT   | MOD_MASK_GUI)
+#define MOD_MASK_CSA             (MOD_MASK_CTRL  | MOD_MASK_SHIFT | MOD_MASK_ALT)
+#define MOD_MASK_CSG             (MOD_MASK_CTRL  | MOD_MASK_SHIFT | MOD_MASK_GUI)
+#define MOD_MASK_CAG             (MOD_MASK_CTRL  | MOD_MASK_ALT   | MOD_MASK_GUI)
+#define MOD_MASK_SAG             (MOD_MASK_SHIFT | MOD_MASK_ALT   | MOD_MASK_GUI)
+#define MOD_MASK_CSAG            (MOD_MASK_CTRL  | MOD_MASK_SHIFT | MOD_MASK_ALT | MOD_MASK_GUI)
+
 #define FN_BIT(code)             (1 << FN_INDEX(code))
 #define FN_INDEX(code)           ((code) - KC_FN0)
 #define FN_MIN                   KC_FN0
@@ -174,6 +190,10 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #define KC_BRIU KC_BRIGHTNESS_UP
 #define KC_BRID KC_BRIGHTNESS_DOWN
 
+/* System Specific */
+#define KC_BRMU KC_PAUSE
+#define KC_BRMD KC_SCROLLLOCK
+
 /* Mouse Keys */
 #define KC_MS_U KC_MS_UP
 #define KC_MS_D KC_MS_DOWN
diff --git a/tmk_core/common/progmem.h b/tmk_core/common/progmem.h
index dcc9efb3ce..de93138397 100644
--- a/tmk_core/common/progmem.h
+++ b/tmk_core/common/progmem.h
@@ -5,9 +5,9 @@
 #   include <avr/pgmspace.h>
 #else
 #   define PROGMEM
-#   define pgm_read_byte(p)     *((unsigned char*)p)
-#   define pgm_read_word(p)     *((uint16_t*)p)
-#   define pgm_read_dword(p)    *((uint32_t*)p)
+#   define pgm_read_byte(p)     *((unsigned char*)(p))
+#   define pgm_read_word(p)     *((uint16_t*)(p))
+#   define pgm_read_dword(p)    *((uint32_t*)(p))
 #endif
 
 #endif
diff --git a/tmk_core/common/wait.h b/tmk_core/common/wait.h
index a7cded9420..a77840bcef 100644
--- a/tmk_core/common/wait.h
+++ b/tmk_core/common/wait.h
@@ -15,6 +15,10 @@ extern "C" {
 #   include "ch.h"
 #   define wait_ms(ms) chThdSleepMilliseconds(ms)
 #   define wait_us(us) chThdSleepMicroseconds(us)
+#elif defined PROTOCOL_ARM_ATSAM
+#   include "clks.h"
+#   define wait_ms(ms) CLK_delay_ms(ms)
+#   define wait_us(us) CLK_delay_us(us)
 #elif defined(__arm__)
 #   include "wait_api.h"
 #else  // Unit tests
diff --git a/tmk_core/protocol/arm_atsam/arm_atsam_protocol.h b/tmk_core/protocol/arm_atsam/arm_atsam_protocol.h
index 2ba0991749..928af8c7e1 100644
--- a/tmk_core/protocol/arm_atsam/arm_atsam_protocol.h
+++ b/tmk_core/protocol/arm_atsam/arm_atsam_protocol.h
@@ -21,8 +21,10 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "samd51j18a.h"
 #include "md_bootloader.h"
 
+#include "timer.h"
 #include "d51_util.h"
 #include "clks.h"
+#include "wait.h"
 #include "adc.h"
 #include "i2c_master.h"
 #include "spi.h"
diff --git a/tmk_core/protocol/arm_atsam/clks.c b/tmk_core/protocol/arm_atsam/clks.c
index 8768d0a99e..1ff318e59b 100644
--- a/tmk_core/protocol/arm_atsam/clks.c
+++ b/tmk_core/protocol/arm_atsam/clks.c
@@ -21,8 +21,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 volatile clk_t system_clks;
 volatile uint64_t ms_clk;
-
-volatile uint8_t us_delay_done;
+uint32_t usec_delay_mult;
+#define USEC_DELAY_LOOP_CYCLES 3 //Sum of instruction cycles in us delay loop
 
 const uint32_t sercom_apbbase[] = {(uint32_t)SERCOM0,(uint32_t)SERCOM1,(uint32_t)SERCOM2,(uint32_t)SERCOM3,(uint32_t)SERCOM4,(uint32_t)SERCOM5};
 const uint8_t sercom_pchan[] = {7, 8, 23, 24, 34, 35};
@@ -73,6 +73,9 @@ void CLK_oscctrl_init(void)
 
     system_clks.freq_gclk[0] = system_clks.freq_dpll[0];
 
+    usec_delay_mult = system_clks.freq_gclk[0] / (USEC_DELAY_LOOP_CYCLES * 1000000);
+    if (usec_delay_mult < 1) usec_delay_mult = 1; //Never allow a multiplier of zero
+
     DBGC(DC_CLK_OSC_INIT_COMPLETE);
 }
 
@@ -158,23 +161,11 @@ void TC4_Handler()
     }
 }
 
-void TC5_Handler()
-{
-    if (TC5->COUNT16.INTFLAG.bit.MC0)
-    {
-        TC5->COUNT16.INTFLAG.reg = TC_INTENCLR_MC0;
-        us_delay_done = 1;
-        TC5->COUNT16.CTRLA.bit.ENABLE = 0;
-        while (TC5->COUNT16.SYNCBUSY.bit.ENABLE) {}
-    }
-}
-
 uint32_t CLK_enable_timebase(void)
 {
     Gclk *pgclk = GCLK;
     Mclk *pmclk = MCLK;
     Tc *ptc4 = TC4;
-    Tc *ptc5 = TC5;
     Tc *ptc0 = TC0;
     Evsys *pevsys = EVSYS;
 
@@ -189,11 +180,6 @@ uint32_t CLK_enable_timebase(void)
     pgclk->PCHCTRL[TC4_GCLK_ID].bit.GEN = GEN_TC45;
     pgclk->PCHCTRL[TC4_GCLK_ID].bit.CHEN = 1;
 
-    //unmask TC5 sourcegclk2 to TC5
-    pmclk->APBCMASK.bit.TC5_ = 1;
-    pgclk->PCHCTRL[TC5_GCLK_ID].bit.GEN = GEN_TC45;
-    pgclk->PCHCTRL[TC5_GCLK_ID].bit.CHEN = 1;
-
     //configure TC4
     DBGC(DC_CLK_ENABLE_TIMEBASE_TC4_BEGIN);
     ptc4->COUNT16.CTRLA.bit.ENABLE = 0;
@@ -220,30 +206,6 @@ uint32_t CLK_enable_timebase(void)
 
     DBGC(DC_CLK_ENABLE_TIMEBASE_TC4_COMPLETE);
 
-    //configure TC5
-    DBGC(DC_CLK_ENABLE_TIMEBASE_TC5_BEGIN);
-    ptc5->COUNT16.CTRLA.bit.ENABLE = 0;
-    while (ptc5->COUNT16.SYNCBUSY.bit.ENABLE) { DBGC(DC_CLK_ENABLE_TIMEBASE_TC5_SYNC_DISABLE); }
-    ptc5->COUNT16.CTRLA.bit.SWRST = 1;
-    while (ptc5->COUNT16.SYNCBUSY.bit.SWRST) { DBGC(DC_CLK_ENABLE_TIMEBASE_TC5_SYNC_SWRST_1); }
-    while (ptc5->COUNT16.CTRLA.bit.SWRST) { DBGC(DC_CLK_ENABLE_TIMEBASE_TC5_SYNC_SWRST_2); }
-
-    //CTRLA defaults
-    //CTRLB as default, counting up
-    ptc5->COUNT16.CTRLBCLR.reg = 5;
-    while (ptc5->COUNT16.SYNCBUSY.bit.CTRLB) { DBGC(DC_CLK_ENABLE_TIMEBASE_TC5_SYNC_CLTRB); }
-    //ptc5->COUNT16.DBGCTRL.bit.DBGRUN = 1;
-
-    //wave mode
-    ptc5->COUNT16.WAVE.bit.WAVEGEN = 1; //MFRQ match frequency mode, toggle each CC match
-    //generate event for next stage
-    ptc5->COUNT16.EVCTRL.bit.MCEO0 = 1;
-
-    NVIC_EnableIRQ(TC5_IRQn);
-    ptc5->COUNT16.INTENSET.bit.MC0 = 1;
-
-    DBGC(DC_CLK_ENABLE_TIMEBASE_TC5_COMPLETE);
-
     //unmask TC0,1, sourcegclk2 to TC0,1
     pmclk->APBAMASK.bit.TC0_ = 1;
     pgclk->PCHCTRL[TC0_GCLK_ID].bit.GEN = GEN_TC45;
@@ -289,37 +251,27 @@ uint32_t CLK_enable_timebase(void)
     return 0;
 }
 
-uint32_t CLK_get_ms(void)
+void CLK_delay_us(uint32_t usec)
 {
-    return ms_clk;
-}
-
-void CLK_delay_us(uint16_t usec)
-{
-    us_delay_done = 0;
-
-    if (TC5->COUNT16.CTRLA.bit.ENABLE)
-    {
-        TC5->COUNT16.CTRLA.bit.ENABLE = 0;
-        while (TC5->COUNT16.SYNCBUSY.bit.ENABLE) {}
-    }
-
-    if (usec < 10) usec = 0;
-    else usec -= 10;
-
-    TC5->COUNT16.CC[0].reg = usec;
-    while (TC5->COUNT16.SYNCBUSY.bit.CC0) {}
-
-    TC5->COUNT16.CTRLA.bit.ENABLE = 1;
-    while (TC5->COUNT16.SYNCBUSY.bit.ENABLE) {}
-
-    while (!us_delay_done) {}
+    asm (
+        "CBZ R0, return\n\t"        //If usec == 0, branch to return label
+    );
+    asm (
+        "MULS R0, %0\n\t"           //Multiply R0(usec) by usec_delay_mult and store in R0
+        ".balign 16\n\t"            //Ensure loop is aligned for fastest performance
+        "loop: SUBS R0, #1\n\t"     //Subtract 1 from R0 and update flags (1 cycle)
+        "BNE loop\n\t"              //Branch if non-zero to loop label (2 cycles)  NOTE: USEC_DELAY_LOOP_CYCLES is the sum of loop cycles
+        "return:\n\t"               //Return label
+        : //No output registers
+        : "r" (usec_delay_mult)     //For %0
+    );
+    //Note: BX LR generated
 }
 
 void CLK_delay_ms(uint64_t msec)
 {
-    msec += CLK_get_ms();
-    while (msec > CLK_get_ms()) {}
+    msec += timer_read64();
+    while (msec > timer_read64()) {}
 }
 
 void clk_enable_sercom_apbmask(int sercomn)
diff --git a/tmk_core/protocol/arm_atsam/clks.h b/tmk_core/protocol/arm_atsam/clks.h
index 96819bfdd0..1b01a1764e 100644
--- a/tmk_core/protocol/arm_atsam/clks.h
+++ b/tmk_core/protocol/arm_atsam/clks.h
@@ -77,9 +77,8 @@ void CLK_oscctrl_init(void);
 void CLK_reset_time(void);
 uint32_t CLK_set_gclk_freq(uint8_t gclkn, uint32_t freq);
 uint32_t CLK_enable_timebase(void);
-uint32_t CLK_get_ms(void);
-uint64_t CLK_get_us(void);
-void CLK_delay_us(uint16_t usec);
+uint64_t timer_read64(void);
+void CLK_delay_us(uint32_t usec);
 void CLK_delay_ms(uint64_t msec);
 
 uint32_t CLK_set_spi_freq(uint8_t sercomn, uint32_t freq);
diff --git a/tmk_core/protocol/arm_atsam/i2c_master.c b/tmk_core/protocol/arm_atsam/i2c_master.c
index f608a79cc9..d91a851f37 100644
--- a/tmk_core/protocol/arm_atsam/i2c_master.c
+++ b/tmk_core/protocol/arm_atsam/i2c_master.c
@@ -265,12 +265,12 @@ uint8_t I2C3733_Init_Control(void)
     //USB state machine will enable driver when communication is ready
     I2C3733_Control_Set(0);
 
-    CLK_delay_ms(1);
+    wait_ms(1);
 
     sr_exp_data.bit.IRST = 0;
     SR_EXP_WriteData();
 
-    CLK_delay_ms(1);
+    wait_ms(1);
 
     DBGC(DC_I2C3733_INIT_CONTROL_COMPLETE);
 
diff --git a/tmk_core/protocol/arm_atsam/led_matrix.c b/tmk_core/protocol/arm_atsam/led_matrix.c
index 9b76d8bbc8..04d05af6db 100644
--- a/tmk_core/protocol/arm_atsam/led_matrix.c
+++ b/tmk_core/protocol/arm_atsam/led_matrix.c
@@ -504,11 +504,11 @@ void led_matrix_task(void)
     if (led_enabled)
     {
         //If an update may run and frame processing has completed
-        if (CLK_get_ms() >= led_next_run && led_cur == lede)
+        if (timer_read64() >= led_next_run && led_cur == lede)
         {
             uint8_t drvid;
 
-            led_next_run = CLK_get_ms() + LED_UPDATE_RATE;  //Set next frame update time
+            led_next_run = timer_read64() + LED_UPDATE_RATE;  //Set next frame update time
 
             //NOTE: GCR does not need to be timed with LED processing, but there is really no harm
             if (gcr_actual != gcr_actual_last)
diff --git a/tmk_core/protocol/arm_atsam/main_arm_atsam.c b/tmk_core/protocol/arm_atsam/main_arm_atsam.c
index 2bda7d7c7b..