qmk · noroadsleft · Nov 8, 2020 · Aug 29, 2020 · Aug 31, 2020 · Sep 2, 2020
diff --git a/build_test.mk b/build_test.mk
@@ -49,6 +49,7 @@ endif
 
 include common_features.mk
 include $(TMK_PATH)/common.mk
+include $(QUANTUM_PATH)/sequencer/tests/rules.mk
 include $(QUANTUM_PATH)/serial_link/tests/rules.mk
 ifneq ($(filter $(FULL_TESTS),$(TEST)),)
 include build_full_test.mk

diff --git a/common.mk b/common.mk
@@ -21,4 +21,5 @@ COMMON_VPATH += $(QUANTUM_PATH)/keymap_extras
 COMMON_VPATH += $(QUANTUM_PATH)/audio
 COMMON_VPATH += $(QUANTUM_PATH)/process_keycode
 COMMON_VPATH += $(QUANTUM_PATH)/api
+COMMON_VPATH += $(QUANTUM_PATH)/sequencer
 COMMON_VPATH += $(DRIVER_PATH)
diff --git a/common_features.mk b/common_features.mk
@@ -38,6 +38,13 @@ ifeq ($(strip $(AUDIO_ENABLE)), yes)
     SRC += $(QUANTUM_DIR)/audio/luts.c
 endif
 
+ifeq ($(strip $(SEQUENCER_ENABLE)), yes)
+    OPT_DEFS += -DSEQUENCER_ENABLE
+    MUSIC_ENABLE = yes
+    SRC += $(QUANTUM_DIR)/sequencer/sequencer.c
+    SRC += $(QUANTUM_DIR)/process_keycode/process_sequencer.c
+endif
+
 ifeq ($(strip $(MIDI_ENABLE)), yes)
     OPT_DEFS += -DMIDI_ENABLE
     MUSIC_ENABLE = yes
@@ -428,8 +435,10 @@ ifeq ($(strip $(SPLIT_KEYBOARD)), yes)
         # Functions added via QUANTUM_LIB_SRC are only included in the final binary if they're called.
         # Unused functions are pruned away, which is why we can add multiple drivers here without bloat.
         ifeq ($(PLATFORM),AVR)
-            QUANTUM_LIB_SRC += i2c_master.c \
-                               i2c_slave.c
+            ifneq ($(NO_I2C),yes)
+                QUANTUM_LIB_SRC += i2c_master.c \
+                                   i2c_slave.c
+            endif
         endif
 
         SERIAL_DRIVER ?= bitbang

diff --git a/docs/_summary.md b/docs/_summary.md
@@ -79,6 +79,7 @@
     * [One Shot Keys](one_shot_keys.md)
     * [Pointing Device](feature_pointing_device.md)
     * [Raw HID](feature_rawhid.md)
+    * [Sequencer](feature_sequencer.md)
     * [Swap Hands](feature_swap_hands.md)
     * [Tap Dance](feature_tap_dance.md)
     * [Tap-Hold Configuration](tap_hold.md)

diff --git a/docs/feature_sequencer.md b/docs/feature_sequencer.md
@@ -0,0 +1,88 @@
+# Sequencer
+
+Since QMK has experimental support for MIDI, you can now turn your keyboard into a [step sequencer](https://en.wikipedia.org/wiki/Music_sequencer#Step_sequencers)!
+
+!> **IMPORTANT:** This feature is highly experimental, it has only been tested on a Planck EZ so far. Also, the scope will be limited to support the drum machine use-case to start with.
+
+## Enable the step sequencer
+
+Add the following line to your `rules.mk`:
+
+```make
+SEQUENCER_ENABLE = yes
+```
+
+By default the sequencer has 16 steps, but you can override this setting in your `config.h`:
+
+```c
+#define SEQUENCER_STEPS 32
+```
+
+## Tracks
+
+You can program up to 8 independent tracks with the step sequencer. Select the tracks you want to edit, enable or disable some steps, and start the sequence!
+
+## Resolutions
+
+While the tempo defines the absolute speed at which the sequencer goes through the steps, the resolution defines the granularity of these steps (from coarser to finer).
+
+|Resolution   |Description            |
+|----------   |-----------            |
+|`SQ_RES_2`   |Every other beat       |
+|`SQ_RES_2T`  |Every 1.5 beats        |
+|`SQ_RES_4`   |Every beat             |
+|`SQ_RES_4T`  |Three times per 2 beats|
+|`SQ_RES_8`   |Twice per beat         |
+|`SQ_RES_8T`  |Three times per beat   |
+|`SQ_RES_16`  |Four times per beat    |
+|`SQ_RES_16T` |Six times per beat     |
+|`SQ_RES_32`  |Eight times per beat   |
+
+## Keycodes
+
+|Keycode  |Description                                        |
+|-------  |-----------                                        |
+|`SQ_ON`  |Start the step sequencer                           |
+|`SQ_OFF` |Stop the step sequencer                            |
+|`SQ_TOG` |Toggle the step sequencer playback                 |
+|`SQ_SALL`|Enable all the steps                               |
+|`SQ_SCLR`|Disable all the steps                              |
+|`SQ_S(n)`|Toggle the step `n`                                |
+|`SQ_TMPD`|Decrease the tempo                                 |
+|`SQ_TMPU`|Increase the tempo                                 |
+|`SQ_R(n)`|Set the resolution to n                            |
+|`SQ_RESD`|Change to the slower resolution                    |
+|`SQ_RESU`|Change to the faster resolution                    |
+|`SQ_T(n)`|Set `n` as the only active track or deactivate all |
+
+## Functions
+
+|Function                                                             |Description                                            |
+|--------                                                             |-----------                                            |
+|`bool is_sequencer_on(void);`                                        |Return whether the sequencer is playing                |
+|`void sequencer_toggle(void);`                                       |Toggle the step sequencer playback                     |
+|`void sequencer_on(void);`                                           |Start the step sequencer                               |
+|`void sequencer_off(void);`                                          |Stop the step sequencer                                |
+|`bool is_sequencer_step_on(uint8_t step);`                           |Return whether the step is currently enabled           |
+|`void sequencer_set_step(uint8_t step, bool value);`                 |Enable or disable the step                             |
+|`void sequencer_set_step_on();`                                      |Enable the step                                        |
+|`void sequencer_set_step_off();`                                     |Disable the step                                       |
+|`void sequencer_toggle_step(uint8_t step);`                          |Toggle the step                                        |
+|`void sequencer_set_all_steps(bool value);`                          |Enable or disable all the steps                        |
+|`void sequencer_set_all_steps_on();`                                 |Enable all the steps                                   |
+|`void sequencer_set_all_steps_off();`                                |Disable all the steps                                  |
+|`uint8_t sequencer_get_tempo(void);`                                 |Return the current tempo                               |
+|`void sequencer_set_tempo(uint8_t tempo);`                           |Set the tempo to `tempo` (between 1 and 255)           |
+|`void sequencer_increase_tempo(void);`                               |Increase the tempo                                     |
+|`void sequencer_decrease_tempo(void);`                               |Decrease the tempo                                     |
+|`sequencer_resolution_t sequencer_get_resolution(void);`             |Return the current resolution                          |
+|`void sequencer_set_resolution(sequencer_resolution_t resolution);`  |Set the resolution to `resolution`                     |
+|`void sequencer_increase_resolution(void);`                          |Change to the faster resolution                        |
+|`void sequencer_decrease_resolution(void);`                          |Change to the slower resolution                        |
+|`bool is_sequencer_track_active(uint8_t track);`                     |Return whether the track is active                     |
+|`void sequencer_set_track_activation(uint8_t track, bool value);`    |Activate or deactivate the `track`                     |
+|`void sequencer_toggle_track_activation(uint8_t track);`             |Toggle the `track`                                     |
+|`void sequencer_activate_track(uint8_t track);`                      |Activate the `track`                                   |
+|`void sequencer_deactivate_track(uint8_t track);`                    |Deactivate the `track`                                 |
+|`void sequencer_toggle_single_active_track(uint8_t track);`          |Set `track` as the only active track or deactivate all |
+
diff --git a/drivers/avr/serial.c b/drivers/avr/serial.c
@@ -20,11 +20,11 @@
 
 #ifdef SOFT_SERIAL_PIN
 
-#    ifdef __AVR_ATmega32U4__
-// if using ATmega32U4 I2C, can not use PD0 and PD1 in soft serial.
+#    if defined(__AVR_ATmega16U2__) || defined(__AVR_ATmega32U2__) || defined(__AVR_ATmega16U4__) || defined(__AVR_ATmega32U4__)
+// if using ATmegaxxU4 I2C, can not use PD0 and PD1 in soft serial.
 #        ifdef USE_AVR_I2C
 #            if SOFT_SERIAL_PIN == D0 || SOFT_SERIAL_PIN == D1
-#                error Using ATmega32U4 I2C, so can not use PD0, PD1
+#                error Using ATmegaxxU4 I2C, so can not use PD0, PD1
 #            endif
 #        endif
 
@@ -52,7 +52,7 @@
 #                define EICRx_BIT (~(_BV(ISC30) | _BV(ISC31)))
 #                define SERIAL_PIN_INTERRUPT INT3_vect
 #            endif
-#        elif SOFT_SERIAL_PIN == E6
+#        elif (defined(__AVR_ATmega16U4__) || defined(__AVR_ATmega32U4__)) && SOFT_SERIAL_PIN == E6
 #            define EIMSK_BIT _BV(INT6)
 #            define EICRx_BIT (~(_BV(ISC60) | _BV(ISC61)))
 #            define SERIAL_PIN_INTERRUPT INT6_vect
@@ -61,7 +61,7 @@
 #        endif
 
 #    else
-#        error serial.c now support ATmega32U4 only
+#        error serial.c currently only supports ATmegaxxU2 and ATmegaxxU4
 #    endif
 
 #    define ALWAYS_INLINE __attribute__((always_inline))

diff --git a/quantum/mcu_selection.mk b/quantum/mcu_selection.mk
@@ -252,6 +252,9 @@ ifneq (,$(filter $(MCU),atmega16u2 atmega32u2 atmega16u4 atmega32u4 at90usb646 a
   ifeq (,$(filter $(NO_INTERRUPT_CONTROL_ENDPOINT),yes))
     OPT_DEFS += -DINTERRUPT_CONTROL_ENDPOINT
   endif
+  ifneq (,$(filter $(MCU),atmega16u2 atmega32u2))
+    NO_I2C = yes
+  endif
 endif
 
 ifneq (,$(filter $(MCU),atmega32a))

diff --git a/quantum/process_keycode/process_midi.c b/quantum/process_keycode/process_midi.c
@@ -41,12 +41,12 @@ static int8_t   midi_modulation_step;
 static uint16_t midi_modulation_timer;
 midi_config_t   midi_config;
 
-inline uint8_t compute_velocity(uint8_t setting) { return (setting + 1) * (128 / (MIDI_VELOCITY_MAX - MIDI_VELOCITY_MIN + 1)); }
+inline uint8_t compute_velocity(uint8_t setting) { return setting * (128 / (MIDI_VELOCITY_MAX - MIDI_VELOCITY_MIN)); }
 
 void midi_init(void) {
     midi_config.octave              = MI_OCT_2 - MIDI_OCTAVE_MIN;
     midi_config.transpose           = 0;
-    midi_config.velocity            = (MIDI_VELOCITY_MAX - MIDI_VELOCITY_MIN);
+    midi_config.velocity            = 127;
     midi_config.channel             = 0;
     midi_config.modulation_interval = 8;
 
@@ -66,7 +66,7 @@ bool process_midi(uint16_t keycode, keyrecord_t *record) {
         case MIDI_TONE_MIN ... MIDI_TONE_MAX: {
             uint8_t channel  = midi_config.channel;
             uint8_t tone     = keycode - MIDI_TONE_MIN;
-            uint8_t velocity = compute_velocity(midi_config.velocity);
+            uint8_t velocity = midi_config.velocity;
             if (record->event.pressed) {
                 uint8_t note = midi_compute_note(keycode);
                 midi_send_noteon(&midi_device, channel, note, velocity);
@@ -122,19 +122,30 @@ bool process_midi(uint16_t keycode, keyrecord_t *record) {
             return false;
         case MIDI_VELOCITY_MIN ... MIDI_VELOCITY_MAX:
             if (record->event.pressed) {
-                midi_config.velocity = keycode - MIDI_VELOCITY_MIN;
+                midi_config.velocity = compute_velocity(keycode - MIDI_VELOCITY_MIN);
                 dprintf("midi velocity %d\n", midi_config.velocity);
             }
             return false;
         case MI_VELD:
             if (record->event.pressed && midi_config.velocity > 0) {
-                midi_config.velocity--;
+                if (midi_config.velocity == 127) {
+                    midi_config.velocity -= 10;
+                } else if (midi_config.velocity > 12) {
+                    midi_config.velocity -= 13;
+                } else {
+                    midi_config.velocity = 0;
+                }
+
                 dprintf("midi velocity %d\n", midi_config.velocity);
             }
             return false;
         case MI_VELU:
-            if (record->event.pressed) {
-                midi_config.velocity++;
+            if (record->event.pressed && midi_config.velocity < 127) {
+                if (midi_config.velocity < 115) {
+                    midi_config.velocity += 13;
+                } else {
+                    midi_config.velocity = 127;
+                }
                 dprintf("midi velocity %d\n", midi_config.velocity);
             }
             return false;

diff --git a/quantum/process_keycode/process_midi.h b/quantum/process_keycode/process_midi.h
@@ -35,7 +35,7 @@ typedef union {
     struct {
         uint8_t octave : 4;
         int8_t  transpose : 4;
-        uint8_t velocity : 4;
+        uint8_t velocity : 7;
         uint8_t channel : 4;
         uint8_t modulation_interval : 4;
     };

diff --git a/quantum/process_keycode/process_sequencer.c b/quantum/process_keycode/process_sequencer.c
@@ -0,0 +1,62 @@
+/* Copyright 2020 Rodolphe Belouin
+ *
+ * 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 "process_sequencer.h"
+
+bool process_sequencer(uint16_t keycode, keyrecord_t *record) {
+    if (record->event.pressed) {
+        switch (keycode) {
+            case SQ_ON:
+                sequencer_on();
+                return false;
+            case SQ_OFF:
+                sequencer_off();
+                return false;
+            case SQ_TOG:
+                sequencer_toggle();
+                return false;
+            case SQ_TMPD:
+                sequencer_decrease_tempo();
+                return false;
+            case SQ_TMPU:
+                sequencer_increase_tempo();
+                return false;
+            case SEQUENCER_RESOLUTION_MIN ... SEQUENCER_RESOLUTION_MAX:
+                sequencer_set_resolution(keycode - SEQUENCER_RESOLUTION_MIN);
+                return false;
+            case SQ_RESD:
+                sequencer_decrease_resolution();
+                return false;
+            case SQ_RESU:
+                sequencer_increase_resolution();
+                return false;
+            case SQ_SALL:
+                sequencer_set_all_steps_on();
+                return false;
+            case SQ_SCLR:
+                sequencer_set_all_steps_off();
+                return false;
+            case SEQUENCER_STEP_MIN ... SEQUENCER_STEP_MAX:
+                sequencer_toggle_step(keycode - SEQUENCER_STEP_MIN);
+                return false;
+            case SEQUENCER_TRACK_MIN ... SEQUENCER_TRACK_MAX:
+                sequencer_toggle_single_active_track(keycode - SEQUENCER_TRACK_MIN);
+                return false;
+        }
+    }
+
+    return true;
+}
diff --git a/quantum/process_keycode/process_sequencer.h b/quantum/process_keycode/process_sequencer.h
@@ -0,0 +1,21 @@
+/* Copyright 2020 Rodolphe Belouin
+ *
+ * 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/>.
+ */
+
+#pragma once
+
+#include "quantum.h"
+
+bool process_sequencer(uint16_t keycode, keyrecord_t *record);
diff --git a/quantum/quantum.c b/quantum/quantum.c
@@ -229,6 +229,9 @@ bool process_record_quantum(keyrecord_t *record) {
             process_record_via(keycode, record) &&
 #endif
             process_record_kb(keycode, record) &&
+#if defined(SEQUENCER_ENABLE)
+            process_sequencer(keycode, record) &&
+#endif
 #if defined(MIDI_ENABLE) && defined(MIDI_ADVANCED)
             process_midi(keycode, record) &&
 #endif
@@ -633,6 +636,10 @@ void matrix_scan_quantum() {
     matrix_scan_music();
 #endif
 
+#ifdef SEQUENCER_ENABLE
+    matrix_scan_sequencer();
+#endif
+
 #ifdef TAP_DANCE_ENABLE
     matrix_scan_tap_dance();
 #endif

diff --git a/quantum/quantum.h b/quantum/quantum.h
@@ -68,6 +68,11 @@ extern layer_state_t default_layer_state;
 extern layer_state_t layer_state;
 #endif
 
+#if defined(SEQUENCER_ENABLE)
+#    include "sequencer.h"
+#    include "process_sequencer.h"
+#endif
+
 #if defined(MIDI_ENABLE) && defined(MIDI_ADVANCED)
 #    include "process_midi.h"
 #endif