Merge pull request #45 from a2/simulator-buzzer

Implement buzzer methods with AudioContext API

12 files changed, 218 insertions, 65 deletions

diff --git a/apps/buzzer-test/app.c b/apps/buzzer-test/app.c
index 65d2356c..2946b646 100644
--- a/apps/buzzer-test/app.c
+++ b/apps/buzzer-test/app.c
@@ -115,7 +115,7 @@ bool app_loop(void) {
             900,
         };
         application_state.play = false;
-        for(size_t i = 0; i < sizeof(rains); i++) {
+        for(size_t i = 0, count = sizeof(rains) / sizeof(rains[0]); i < count; i++) {
             char buf[9] = {0};
             if (rains[i] == BUZZER_NOTE_REST) {
                 printf("rest for %d ms\n", durations[i]);
diff --git a/make.mk b/make.mk
index 85d38fea..aeada13f 100644
--- a/make.mk
+++ b/make.mk
@@ -120,6 +120,7 @@ SRCS += \
   $(TOP)/watch-library/shared/driver/lis2dh.c \
   $(TOP)/watch-library/shared/driver/lis2dw.c \
   $(TOP)/watch-library/shared/driver/spiflash.c \
+  $(TOP)/watch-library/shared/watch/watch_private_buzzer.c \
   $(TOP)/watch-library/shared/watch/watch_private_display.c \
   $(TOP)/watch-library/shared/watch/watch_utility.c \
 
@@ -137,6 +138,7 @@ INCLUDES += \
   -I$(TOP)/watch-library/shared/driver/ \
   -I$(TOP)/watch-library/shared/config/ \
   -I$(TOP)/watch-library/shared/watch/ \
+  -I$(TOP)/watch-library/simulator/watch/ \
   -I$(TOP)/watch-library/simulator/hpl/port/ \
   -I$(TOP)/watch-library/hardware/include/component \
   -I$(TOP)/watch-library/hardware/hal/include/ \
@@ -159,6 +161,7 @@ SRCS += \
   $(TOP)/watch-library/simulator/watch/watch_deepsleep.c \
   $(TOP)/watch-library/simulator/watch/watch_private.c \
   $(TOP)/watch-library/simulator/watch/watch.c \
+  $(TOP)/watch-library/shared/watch/watch_private_buzzer.c \
   $(TOP)/watch-library/shared/watch/watch_private_display.c \
   $(TOP)/watch-library/shared/watch/watch_utility.c \
 
diff --git a/rules.mk b/rules.mk
index cd42a433..1aa135a8 100644
--- a/rules.mk
+++ b/rules.mk
@@ -13,6 +13,7 @@ endif
 $(BUILD)/$(BIN).html: $(OBJS)
 	@echo HTML $@
 	@$(CC) $(LDFLAGS) $(OBJS) $(LIBS) -o $@ \
+		-s ASYNCIFY=1 \
 		-s EXPORTED_FUNCTIONS=_main \
 		--shell-file=$(TOP)/watch-library/simulator/shell.html
 
diff --git a/watch-library/hardware/watch/watch_buzzer.c b/watch-library/hardware/watch/watch_buzzer.c
index a275b00d..c06242ff 100644
--- a/watch-library/hardware/watch/watch_buzzer.c
+++ b/watch-library/hardware/watch/watch_buzzer.c
@@ -47,10 +47,6 @@ inline void watch_set_buzzer_off(void) {
     gpio_set_pin_function(BUZZER, GPIO_PIN_FUNCTION_OFF);
 }
 
-// note: the buzzer uses a 1 MHz clock. these values were determined by dividing 1,000,000 by the target frequency.
-// i.e. for a 440 Hz tone (A4 on the piano), 1MHz/440Hz = 2273
-const uint16_t NotePeriods[108] = {18182,17161,16197,15288,14430,13620,12857,12134,11453,10811,10204,9631,9091,8581,8099,7645,7216,6811,6428,6068,5727,5405,5102,4816,4545,4290,4050,3822,3608,3405,3214,3034,2863,2703,2551,2408,2273,2145,2025,1911,1804,1703,1607,1517,1432,1351,1276,1204,1136,1073,1012,956,902,851,804,758,716,676,638,602,568,536,506,478,451,426,402,379,358,338,319,301,284,268,253,239,225,213,201,190,179,169,159,150,142,134,127};
-
 void watch_buzzer_play_note(BuzzerNote note, uint16_t duration_ms) {
     if (note == BUZZER_NOTE_REST) {
         watch_set_buzzer_off();
diff --git a/watch-library/shared/watch/watch_private_buzzer.c b/watch-library/shared/watch/watch_private_buzzer.c
new file mode 100644
index 00000000..0618f425
--- /dev/null
+++ b/watch-library/shared/watch/watch_private_buzzer.c
@@ -0,0 +1,28 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2022 Joey Castillo
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#include "driver_init.h"
+
+// note: the buzzer uses a 1 MHz clock. these values were determined by dividing 1,000,000 by the target frequency.
+// i.e. for a 440 Hz tone (A4 on the piano), 1MHz/440Hz = 2273
+const uint16_t NotePeriods[108] = {18182,17161,16197,15288,14430,13620,12857,12134,11453,10811,10204,9631,9091,8581,8099,7645,7216,6811,6428,6068,5727,5405,5102,4816,4545,4290,4050,3822,3608,3405,3214,3034,2863,2703,2551,2408,2273,2145,2025,1911,1804,1703,1607,1517,1432,1351,1276,1204,1136,1073,1012,956,902,851,804,758,716,676,638,602,568,536,506,478,451,426,402,379,358,338,319,301,284,268,253,239,225,213,201,190,179,169,159,150,142,134,127};
diff --git a/watch-library/simulator/main.c b/watch-library/simulator/main.c
index 5596bf82..14bf44e6 100644
--- a/watch-library/simulator/main.c
+++ b/watch-library/simulator/main.c
@@ -24,37 +24,81 @@
 
 #include <stdio.h>
 #include "watch.h"
+#include "watch_main_loop.h"
 
 #include <emscripten.h>
 #include <emscripten/html5.h>
 
+#define ANIMATION_FRAME_ID_IS_VALID(id) ((id) >= 0)
+#define ANIMATION_FRAME_ID_INVALID (-1)
+#define ANIMATION_FRAME_ID_SUSPENDED (-2)
+
 static bool sleeping = true;
+static volatile long animation_frame_id = ANIMATION_FRAME_ID_INVALID;
+
+// make compiler happy
+static void main_loop_set_sleeping(bool sleeping);
+static EM_BOOL main_loop(double time, void *userData);
+
+static inline void request_next_frame(void) {
+    if (animation_frame_id == ANIMATION_FRAME_ID_INVALID) {
+        animation_frame_id = emscripten_request_animation_frame(main_loop, NULL);
+    }
+}
 
 static EM_BOOL main_loop(double time, void *userData) {
+    if (main_loop_is_sleeping()) {
+        request_next_frame();
+        return EM_FALSE;
+    }
+
     if (sleeping) {
         sleeping = false;
         app_wake_from_standby();
     }
 
+    animation_frame_id = ANIMATION_FRAME_ID_INVALID;
     bool can_sleep = app_loop();
 
     if (can_sleep) {
         app_prepare_for_standby();
         sleeping = true;
+        animation_frame_id = ANIMATION_FRAME_ID_INVALID;
         return EM_FALSE;
     }
 
-    return EM_TRUE;
+    request_next_frame();
+    return EM_FALSE;
 }
 
-// make compiler happy
-void resume_main_loop(void);
-
-EMSCRIPTEN_KEEPALIVE
 void resume_main_loop(void) {
-    if (sleeping) {
-        emscripten_request_animation_frame_loop(main_loop, NULL);
+    if (!ANIMATION_FRAME_ID_IS_VALID(animation_frame_id)) {
+        animation_frame_id = emscripten_request_animation_frame(main_loop, NULL);
+    }
+}
+
+void suspend_main_loop(void) {
+    if (ANIMATION_FRAME_ID_IS_VALID(animation_frame_id)) {
+        emscripten_cancel_animation_frame(animation_frame_id);
     }
+
+    animation_frame_id = ANIMATION_FRAME_ID_SUSPENDED;
+}
+
+void main_loop_sleep(uint32_t ms) {
+    main_loop_set_sleeping(true);
+    emscripten_sleep(ms);
+    main_loop_set_sleeping(false);
+}
+
+bool main_loop_is_sleeping(void) {
+    return EM_ASM_INT({ return Module['suspended']; }) != 0;
+}
+
+static void main_loop_set_sleeping(bool sleeping) {
+    EM_ASM({
+        Module['suspended'] = $0;
+    }, sleeping);
 }
 
 int main(void) {
diff --git a/watch-library/simulator/watch/watch_buzzer.c b/watch-library/simulator/watch/watch_buzzer.c
index f19e1928..1c95a96d 100644
--- a/watch-library/simulator/watch/watch_buzzer.c
+++ b/watch-library/simulator/watch/watch_buzzer.c
@@ -23,38 +23,82 @@
  */
 
 #include "watch_buzzer.h"
+#include "watch_main_loop.h"
 
-inline void watch_enable_buzzer(void) {
-    // TODO: (a2) hook to UI
+#include <emscripten.h>
+
+static bool buzzer_enabled = false;
+static uint32_t buzzer_period;
+
+void watch_enable_buzzer(void) {
+    buzzer_enabled = true;
+    buzzer_period = NotePeriods[BUZZER_NOTE_A4];
+
+    EM_ASM({
+        Module['audioContext'] = new (window.AudioContext || window.webkitAudioContext)();
+    });
 }
-inline void watch_set_buzzer_period(uint32_t period) {
-    // TODO: (a2) hook to UI
+
+void watch_set_buzzer_period(uint32_t period) {
+    if (!buzzer_enabled) return;
+    buzzer_period = period;
 }
 
 void watch_disable_buzzer(void) {
-    _watch_disable_tcc();
-}
+    buzzer_enabled = false;
+    buzzer_period = NotePeriods[BUZZER_NOTE_A4];
 
-inline void watch_set_buzzer_on(void) {
-    // TODO: (a2) hook to UI
+    EM_ASM({
+        if (Module['audioContext']) {
+            Module['audioContext'].close();
+            Module['audioContext'] = null;
+        }
+    });
 }
 
-inline void watch_set_buzzer_off(void) {
-    // TODO: (a2) hook to UI
+void watch_set_buzzer_on(void) {
+    if (!buzzer_enabled) return;
+
+    EM_ASM({
+        const audioContext = Module['audioContext'];
+        if (!audioContext) return;
+
+        if (!(audioContext._oscillator && audioContext._gain)) {
+            const oscillator = audioContext.createOscillator();
+            const gain = audioContext.createGain();
+            oscillator.type = 'triangle';
+            oscillator.connect(gain);
+            gain.connect(audioContext.destination);
+            oscillator.start(0);
+
+            audioContext._oscillator = oscillator;
+            audioContext._gain = gain;
+        }
+
+        audioContext._oscillator.frequency.value = 1e6/$0;
+        audioContext._gain.gain.value = 1;
+    }, buzzer_period);
 }
 
-// note: the buzzer uses a 1 MHz clock. these values were determined by dividing 1,000,000 by the target frequency.
-// i.e. for a 440 Hz tone (A4 on the piano), 1MHz/440Hz = 2273
-const uint16_t NotePeriods[108] = {0};
+void watch_set_buzzer_off(void) {
+    if (!buzzer_enabled) return;
+
+    EM_ASM({
+        const audioContext = Module['audioContext'];
+        if (audioContext && audioContext._gain) {
+            audioContext._gain.gain.value = 0;
+        }
+    });
+}
 
 void watch_buzzer_play_note(BuzzerNote note, uint16_t duration_ms) {
     if (note == BUZZER_NOTE_REST) {
         watch_set_buzzer_off();
-    } // else {
-    //     hri_tcc_write_PERBUF_reg(TCC0, NotePeriods[note]);
-    //     hri_tcc_write_CCBUF_reg(TCC0, WATCH_BUZZER_TCC_CHANNEL, NotePeriods[note] / 2);
-    //     watch_set_buzzer_on();
-    // }
-    // delay_ms(duration_ms);
-    // watch_set_buzzer_off();
+    } else {
+        watch_set_buzzer_period(NotePeriods[note]);
+        watch_set_buzzer_on();
+    }
+
+    main_loop_sleep(duration_ms);
+    watch_set_buzzer_off();
 }
diff --git a/watch-library/simulator/watch/watch_deepsleep.c b/watch-library/simulator/watch/watch_deepsleep.c
index 9f409570..a12cf2a6 100644
--- a/watch-library/simulator/watch/watch_deepsleep.c
+++ b/watch-library/simulator/watch/watch_deepsleep.c
@@ -35,6 +35,7 @@ static uint32_t watch_backup_data[8];
 
 void watch_register_extwake_callback(uint8_t pin, ext_irq_cb_t callback, bool level) {
     if (pin == BTN_ALARM) {
+        watch_enable_external_interrupts();
         watch_register_interrupt_callback(pin, callback, level ? INTERRUPT_TRIGGER_RISING : INTERRUPT_TRIGGER_FALLING);
     }
 }
diff --git a/watch-library/simulator/watch/watch_extint.c b/watch-library/simulator/watch/watch_extint.c
index d37059bf..03abe42c 100644
--- a/watch-library/simulator/watch/watch_extint.c
+++ b/watch-library/simulator/watch/watch_extint.c
@@ -23,6 +23,7 @@
  */
 
 #include "watch_extint.h"
+#include "watch_main_loop.h"
 
 #include <emscripten.h>
 #include <emscripten/html5.h>
@@ -41,7 +42,7 @@ static watch_interrupt_trigger external_interrupt_alarm_trigger = INTERRUPT_TRIG
 #define BTN_ID_LIGHT 1
 #define BTN_ID_MODE 2
 static const uint8_t BTN_IDS[] = { BTN_ID_ALARM, BTN_ID_LIGHT, BTN_ID_MODE };
-static void watch_invoke_interrupt_callback(const uint8_t button_id, watch_interrupt_trigger trigger);
+static EM_BOOL watch_invoke_interrupt_callback(const uint8_t button_id, watch_interrupt_trigger trigger);
 
 static EM_BOOL watch_invoke_key_callback(int eventType, const EmscriptenKeyboardEvent *keyEvent, void *userData) {
     if (output_focused || keyEvent->repeat) return EM_FALSE;
@@ -68,23 +69,20 @@ static EM_BOOL watch_invoke_key_callback(int eventType, const EmscriptenKeyboard
     }
 
     watch_interrupt_trigger trigger = eventType == EMSCRIPTEN_EVENT_KEYDOWN ? INTERRUPT_TRIGGER_RISING : INTERRUPT_TRIGGER_FALLING;
-    watch_invoke_interrupt_callback(button_id, trigger);
-    return EM_TRUE;
+    return watch_invoke_interrupt_callback(button_id, trigger);
 }
 
 static EM_BOOL watch_invoke_mouse_callback(int eventType, const EmscriptenMouseEvent *mouseEvent, void *userData) {
     if (eventType == EMSCRIPTEN_EVENT_MOUSEOUT && mouseEvent->buttons == 0) return EM_FALSE;
     uint8_t button_id = *(const char *)userData;
     watch_interrupt_trigger trigger = eventType == EMSCRIPTEN_EVENT_MOUSEDOWN ? INTERRUPT_TRIGGER_RISING : INTERRUPT_TRIGGER_FALLING;
-    watch_invoke_interrupt_callback(button_id, trigger);
-    return EM_TRUE;
+    return watch_invoke_interrupt_callback(button_id, trigger);
 }
 
 static EM_BOOL watch_invoke_touch_callback(int eventType, const EmscriptenTouchEvent *touchEvent, void *userData) {
     uint8_t button_id = *(const char *)userData;
     watch_interrupt_trigger trigger = eventType == EMSCRIPTEN_EVENT_TOUCHSTART ? INTERRUPT_TRIGGER_RISING : INTERRUPT_TRIGGER_FALLING;
-    watch_invoke_interrupt_callback(button_id, trigger);
-    return EM_TRUE;
+    return watch_invoke_interrupt_callback(button_id, trigger);
 }
 
 static EM_BOOL watch_invoke_focus_callback(int eventType, const EmscriptenFocusEvent *focusEvent, void *userData) {
@@ -126,9 +124,7 @@ void watch_disable_external_interrupts(void) {
     external_interrupt_enabled = false;
 }
 
-static void watch_invoke_interrupt_callback(const uint8_t button_id, watch_interrupt_trigger event) {
-    if (!external_interrupt_enabled) return;
-
+static EM_BOOL watch_invoke_interrupt_callback(const uint8_t button_id, watch_interrupt_trigger event) {
     ext_irq_cb_t callback;
     watch_interrupt_trigger trigger;
     uint8_t pin;
@@ -149,7 +145,7 @@ static void watch_invoke_interrupt_callback(const uint8_t button_id, watch_inter
             trigger = external_interrupt_alarm_trigger;
             break;
         default:
-            return;
+            return EM_FALSE;
     }
 
     const bool level = (event & INTERRUPT_TRIGGER_RISING) != 0;
@@ -159,14 +155,18 @@ static void watch_invoke_interrupt_callback(const uint8_t button_id, watch_inter
         $1 ? classList.add(highlight) : classList.remove(highlight);
     }, button_id, level);
 
+    if (!external_interrupt_enabled || main_loop_is_sleeping()) {
+        return EM_FALSE;
+    }
+
     watch_set_pin_level(pin, level);
 
     if (callback && (event & trigger) != 0) {
         callback();
-
-        void resume_main_loop(void);
         resume_main_loop();
     }
+
+    return EM_TRUE;
 }
 
 void watch_register_interrupt_callback(const uint8_t pin, ext_irq_cb_t callback, watch_interrupt_trigger trigger) {
diff --git a/watch-library/simulator/watch/watch_main_loop.h b/watch-library/simulator/watch/watch_main_loop.h
new file mode 100644
index 00000000..82351919
--- /dev/null
+++ b/watch-library/simulator/watch/watch_main_loop.h
@@ -0,0 +1,33 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2022 Joey Castillo
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "driver_init.h"
+
+void suspend_main_loop(void);
+
+void resume_main_loop(void);
+
+void main_loop_sleep(uint32_t ms);
+
+bool main_loop_is_sleeping(void);
diff --git a/watch-library/simulator/watch/watch_rtc.c b/watch-library/simulator/watch/watch_rtc.c
index 573c0ff2..1fe6a78b 100644
--- a/watch-library/simulator/watch/watch_rtc.c
+++ b/watch-library/simulator/watch/watch_rtc.c
@@ -23,15 +23,16 @@
  */
 
 #include "watch_rtc.h"
+#include "watch_main_loop.h"
 
 #include <emscripten.h>
 #include <emscripten/html5.h>
 
 static double time_offset = 0;
-static long tick_callbacks[8];
+static long tick_callbacks[8] = { -1, -1, -1, -1, -1, -1, -1, -1 };
 
-static long alarm_interval_id;
-static long alarm_timeout_id;
+static long alarm_interval_id = -1;
+static long alarm_timeout_id = -1;
 static double alarm_interval;
 ext_irq_cb_t alarm_callback;
 ext_irq_cb_t btn_alarm_callback;
@@ -83,8 +84,6 @@ void watch_rtc_disable_tick_callback(void) {
 static void watch_invoke_periodic_callback(void *userData) {
     ext_irq_cb_t callback = userData;
     callback();
-
-    void resume_main_loop(void);
     resume_main_loop();
 }
 
@@ -100,32 +99,34 @@ void watch_rtc_register_periodic_callback(ext_irq_cb_t callback, uint8_t frequen
 
     // this also maps nicely to an index for our list of tick callbacks.
     double interval = 1000 / frequency; // in msec
+
+    if (tick_callbacks[per_n] != -1) emscripten_clear_interval(tick_callbacks[per_n]);
     tick_callbacks[per_n] = emscripten_set_interval(watch_invoke_periodic_callback, interval, (void *)callback);
 }
 
 void watch_rtc_disable_periodic_callback(uint8_t frequency) {
     if (__builtin_popcount(frequency) != 1) return;
     uint8_t per_n = __builtin_clz(frequency << 24);
-    emscripten_clear_interval(tick_callbacks[per_n]);
-    tick_callbacks[per_n] = 0;
+    if (tick_callbacks[per_n] != -1) {
+        emscripten_clear_interval(tick_callbacks[per_n]);
+        tick_callbacks[per_n] = -1;
+    }
 }
 
 void watch_rtc_disable_all_periodic_callbacks(void) {
     for (int i = 0; i < 8; i++) {
-        if (tick_callbacks[i] != 0) {
+        if (tick_callbacks[i] != -1) {
             emscripten_clear_interval(tick_callbacks[i]);
-            tick_callbacks[i] = 0;
+            tick_callbacks[i] = -1;
         }
     }
 }
 
 static void watch_invoke_alarm_interval_callback(void *userData) {
-    (void)userData;
     if (alarm_callback) alarm_callback();
 }
 
 static void watch_invoke_alarm_callback(void *userData) {
-    (void)userData;
     if (alarm_callback) alarm_callback();
     alarm_interval_id = emscripten_set_interval(watch_invoke_alarm_interval_callback, alarm_interval, NULL);
 }
@@ -182,14 +183,14 @@ void watch_rtc_disable_alarm_callback(void) {
     alarm_callback = NULL;
     alarm_interval = 0;
 
-    if (alarm_timeout_id) {
+    if (alarm_timeout_id != -1) {
         emscripten_clear_timeout(alarm_timeout_id);
-        alarm_timeout_id = 0;
+        alarm_timeout_id = -1;
     }
 
-    if (alarm_interval_id) {
+    if (alarm_interval_id != -1) {
         emscripten_clear_interval(alarm_interval_id);
-        alarm_interval_id = 0;
+        alarm_interval_id = -1;
     }
 }
 
diff --git a/watch-library/simulator/watch/watch_slcd.c b/watch-library/simulator/watch/watch_slcd.c
index 2af96847..5c5a936f 100644
--- a/watch-library/simulator/watch/watch_slcd.c
+++ b/watch-library/simulator/watch/watch_slcd.c
@@ -34,9 +34,9 @@
 
 static char blink_character;
 static bool blink_state;
-static long blink_interval_id;
+static long blink_interval_id = - 1;
 static bool tick_state;
-static long tick_interval_id;
+static long tick_interval_id = -1;
 
 void watch_enable_display(void) {
     watch_clear_display();
@@ -70,6 +70,7 @@ static void watch_invoke_blink_callback(void *userData) {
 }
 
 void watch_start_character_blink(char character, uint32_t duration) {
+    if (blink_interval_id != -1) return;
     watch_display_character(character, 7);
     watch_clear_pixel(2, 10); // clear segment B of position 7 since it can't blink
 
@@ -80,7 +81,7 @@ void watch_start_character_blink(char character, uint32_t duration) {
 
 void watch_stop_blink(void) {
     emscripten_clear_timeout(blink_interval_id);
-    blink_interval_id = 0;
+    blink_interval_id = -1;
     blink_state = false;
 }
 
@@ -96,6 +97,7 @@ static void watch_invoke_tick_callback(void *userData) {
 }
 
 void watch_start_tick_animation(uint32_t duration) {
+    if (tick_interval_id != -1) return;
     watch_display_character(' ', 8);
 
     tick_state = true;
@@ -103,12 +105,12 @@ void watch_start_tick_animation(uint32_t duration) {
 }
 
 bool watch_tick_animation_is_running(void) {
-    return tick_interval_id != 0;
+    return tick_interval_id != -1;
 }
 
 void watch_stop_tick_animation(void) {
     emscripten_clear_timeout(tick_interval_id);
-    tick_interval_id = 0;
+    tick_interval_id = -1;
     tick_state = false;
 
     watch_display_character(' ', 8);