diff --git a/Makefile b/Makefile
index 4b90ef9..c03f194 100644
--- a/Makefile
+++ b/Makefile
@@ -42,7 +42,7 @@ format: .check-name
 
 run-debug: format
 	@rm -f  ${name}/${name}.debug
-	@gcc -std=c99 -o2 ${name}/*.c  -lm -o ${name}/${name}.debug && ./${name}/${name}.debug
+	@gcc -DDEBUG -std=c99 -o2 ${name}/*.c  -lm -o ${name}/${name}.debug && ./${name}/${name}.debug
 
 compile: format
 	@rm -f ${name}/build/CMakeCache.txt
diff --git a/buzzer/CMakeLists.txt b/buzzer/CMakeLists.txt
index 2fabe7d..d6fb81b 100644
--- a/buzzer/CMakeLists.txt
+++ b/buzzer/CMakeLists.txt
@@ -20,9 +20,38 @@ set_target_properties(picotool PROPERTIES
 # Initialise the Raspberry Pi Pico SDK
 pico_sdk_init()
 
+set(FREERTOS_SRC_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/../freertos)
+set(FREERTOS_CONFIG_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/../config)
+
+include(${FREERTOS_SRC_DIRECTORY}/portable/ThirdParty/GCC/RP2350_ARM_NTZ/FreeRTOS_Kernel_import.cmake)
+
+# Include FreeRTOS directories
+include_directories(
+	${FREERTOS_CONFIG_DIRECTORY}
+  ${FREERTOS_SRC_DIRECTORY}/include
+  ${FREERTOS_SRC_DIRECTORY}/portable/ThirdParty/GCC/RP2350_ARM_NTZ/non_secure
+)
+
+set(FREERTOS_SOURCES
+  ${FREERTOS_SRC_DIRECTORY}/event_groups.c
+  ${FREERTOS_SRC_DIRECTORY}/list.c
+  ${FREERTOS_SRC_DIRECTORY}/queue.c
+  ${FREERTOS_SRC_DIRECTORY}/stream_buffer.c
+  ${FREERTOS_SRC_DIRECTORY}/tasks.c
+  ${FREERTOS_SRC_DIRECTORY}/timers.c
+  ${FREERTOS_SRC_DIRECTORY}/portable/MemMang/heap_3.c
+)
+
+set(FREERTOS_PORT_FILES
+    ${FREERTOS_SRC_DIRECTORY}/portable/ThirdParty/GCC/RP2350_ARM_NTZ/non_secure/port.c
+    ${FREERTOS_SRC_DIRECTORY}/portable/ThirdParty/GCC/RP2350_ARM_NTZ/non_secure/portasm.c
+    ${FREERTOS_SRC_DIRECTORY}/portable/ThirdParty/GCC/RP2350_ARM_NTZ/non_secure/mpu_wrappers_v2_asm.c
+)
+
 # Add executable. Default name is the project name, version 0.1
 
-add_executable(buzzer main.c )
+add_executable(buzzer main.c log.c gpio.c jobs.c ${FREERTOS_SOURCES} ${FREERTOS_PORT_FILES})
+add_definitions(-DPICO)
 
 pico_set_program_name(buzzer "buzzer")
 pico_set_program_version(buzzer "0.1")
@@ -33,7 +62,7 @@ pico_enable_stdio_usb(buzzer 1)
 
 # Add the standard library to the build
 target_link_libraries(buzzer
-        pico_stdlib hardware_pwm)
+        pico_stdlib hardware_pwm pico_multicore hardware_exception)
 
 # Add the standard include files to the build
 target_include_directories(buzzer PRIVATE
diff --git a/buzzer/circuit.jpg b/buzzer/circuit.jpg
new file mode 100755
index 0000000..32d2684
Binary files /dev/null and b/buzzer/circuit.jpg differ
diff --git a/buzzer/gpio.c b/buzzer/gpio.c
new file mode 100644
index 0000000..39da6db
--- /dev/null
+++ b/buzzer/gpio.c
@@ -0,0 +1,124 @@
+//#define PICO
+
+#ifdef PICO
+#include <pico/printf.h>
+#include <pico/stdlib.h>
+#include <hardware/pwm.h>
+
+#define DEFAULT_WRAP_LEVEL 20
+#else
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <unistd.h>
+
+#define GPIO_OUT 1
+#define GPIO_IN 0
+
+static size_t GPIO_INPUT_MOCK_COUNTER = 0;
+#endif
+
+#include "gpio.h"
+#include "log.h"
+
+void _sleep_ms(size_t value) {
+#ifdef PICO
+    sleep_ms(value);
+#else
+    usleep(value * 1000);
+#endif
+}
+
+void _sleep_us(size_t value) {
+#ifdef PICO
+    sleep_us(value);
+#else
+    usleep(value);
+#endif
+}
+
+void gpio_set_level(gpio *g, uint16_t level) {
+    if (g->has_pwm && g->direction == GPIO_OUT) {
+        g->level = level;
+        g->state = level > 0;
+#ifdef PICO
+        pwm_set_gpio_level(g->pin, level);
+#else
+        debug("<GPIO.set_level (pin=%ld) (level=%d)>", g->pin, level);
+#endif
+    }
+}
+
+void gpio_set_state(gpio *g, bool state) {
+    if (!g->has_pwm && g->direction == GPIO_OUT) {
+#ifdef PICO
+        gpio_put(g->pin, state);
+#else
+        // must be trace instead
+        // debug("<GPIO.set_state (pin=%ld) (level=%d)>", g->pin, state);
+#endif
+    }
+}
+
+bool gpio_get_input(gpio* g) {
+    if (g->direction == GPIO_IN) {
+#ifdef PICO
+        g->state = gpio_get(g->pin);
+#else
+        int value = rand() % (10 + 1);
+        if (value == 0) {
+            g->state = false;
+            return false;
+        }
+        g->state = GPIO_INPUT_MOCK_COUNTER++ % value == 0;
+        debug("gpio get input (state: %d)", g->state);
+#endif
+        return g->state;
+    }
+    return false;
+}
+
+void blink_failed(size_t pin, uint32_t delay_ms) {
+#ifdef PICO
+    for (;;) {
+        gpio_put(pin, false);
+        _sleep_ms(delay_ms);
+
+        gpio_put(pin, true);
+        _sleep_ms(delay_ms);
+    }
+#else
+    for(;;) {
+        debug("fatal error occurred, please restart the application");
+        _sleep_ms(delay_ms);
+    }
+#endif
+}
+
+void blink_passed(size_t pin, uint32_t delay_ms, char* msg) {
+#ifdef PICO
+    gpio_put(pin, true);
+    _sleep_ms(delay_ms);
+    gpio_put(pin, false);
+    _sleep_ms(delay_ms);
+#else
+    debug(msg);
+#endif
+}
+
+void init_gpio(void) {
+#ifdef PICO
+    stdio_init_all();
+    for (size_t i = 0; i < NB_GPIO; i++) {
+        gpio_init(GPIOS[i]->pin);
+        gpio_set_dir(GPIOS[i]->pin, GPIOS[i]->direction);
+
+        if (GPIOS[i]->has_pwm) {
+            uint slice_num = pwm_gpio_to_slice_num(GPIOS[i]->pin);
+            pwm_set_enabled(slice_num, true);
+            pwm_set_wrap(slice_num, DEFAULT_WRAP_LEVEL);
+        }
+    }
+    blink_passed(GPIOS[0]->pin, 200, "gpios init with success");
+#endif
+}
diff --git a/buzzer/gpio.h b/buzzer/gpio.h
new file mode 100644
index 0000000..238bef8
--- /dev/null
+++ b/buzzer/gpio.h
@@ -0,0 +1,62 @@
+//#define PICO
+
+#ifndef GPIO_H
+#define GPIO_H
+
+#ifdef PICO
+#include <pico/printf.h>
+#include <pico/stdlib.h>
+#include <hardware/pwm.h>
+#include <FreeRTOS.h>
+#include <semphr.h>
+#include <task.h>
+#else
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+#define PICO_DEFAULT_LED_PIN 0
+#define GPIO_OUT 1
+#define GPIO_IN 0
+#endif
+
+#define NB_GPIO 3
+
+typedef struct gpio gpio;
+struct gpio {
+    size_t pin;
+    size_t direction;
+    bool has_pwm;
+    uint16_t level;
+    bool state;
+};
+
+static gpio GPIO_DEFAULT_LED = (gpio) {
+    .pin = PICO_DEFAULT_LED_PIN, .direction = GPIO_OUT, .has_pwm = false, .level = 0, .state = false
+};
+
+static gpio GPIO_BUTTON = (gpio) {
+    .pin = 16, .direction = GPIO_IN, .has_pwm = false, .level = 0, .state = false
+};
+
+static gpio GPIO_BUZZER = (gpio) {
+    .pin = 15, .direction = GPIO_OUT, .has_pwm = false, .level = 0, .state = false
+};
+
+static gpio* GPIOS[NB_GPIO] = {&GPIO_DEFAULT_LED, &GPIO_BUTTON, &GPIO_BUZZER};
+
+void gpio_set_level(gpio *g, uint16_t level);
+void gpio_set_state(gpio *g, bool state);
+bool gpio_get_input(gpio* g);
+
+void init_gpio(void);
+
+void blink_failed(size_t pin, uint32_t delay_ms);
+void blink_passed(size_t pin, uint32_t delay_ms, char* msg);
+
+void _sleep_ms(size_t value);
+void _sleep_us(size_t value);
+
+#endif
\ No newline at end of file
diff --git a/buzzer/jobs.c b/buzzer/jobs.c
new file mode 100644
index 0000000..ce92ca9
--- /dev/null
+++ b/buzzer/jobs.c
@@ -0,0 +1,171 @@
+//#define PICO
+
+#ifdef PICO
+#include <pico/printf.h>
+#include <pico/stdlib.h>
+#include "FreeRTOS.h"
+#include "task.h"
+#include "semphr.h"
+#else
+#include <stdio.h>
+#include <stdbool.h>
+#include <pthread.h>
+#endif
+
+#include "gpio.h"
+#include "jobs.h"
+#include "log.h"
+
+#define BUTTON_BUFFETING_SLEEP_DURATION_MS 20
+
+int init_app_state(AppState *s) {
+    s->action = STOP;
+
+#ifdef PICO
+    s->lock = xSemaphoreCreateMutex();
+#else
+    if (pthread_mutex_init(&s->lock, NULL) != 0) {
+        printf("error: mutex init failed\n");
+        return -1;
+    }
+#endif
+
+    return 0;
+}
+
+int lock(AppState *s) {
+#ifdef PICO
+    if (xSemaphoreTake(s->lock, (TickType_t)10) != pdTRUE) {
+        printf("unable to lock the FreeRTOS task\n");
+        return -1;
+    }
+    return 0;
+#else
+    return pthread_mutex_lock(&s->lock);
+#endif
+}
+
+int release(AppState *s) {
+#ifdef PICO
+    xSemaphoreGive(s->lock);
+    return 0;
+#else
+    return pthread_mutex_unlock(&s->lock);
+#endif
+}
+
+int cancel_task(AppState *s) {
+    debug("stopping task...");
+#ifdef PICO
+    if (s->task != NULL) {
+        vTaskDelete(*s->task);
+        free(s->task);
+        gpio_set_state(GPIOS[2], false);
+        return 0;
+    }
+#else
+    if (s->task != NULL) {
+        if (pthread_cancel(*s->task) != 0) {
+            perror("error: unable to cancel the thread task\n");
+            return -1;
+        }
+
+        if (pthread_join(*s->task, NULL) != 0) {
+            perror("error: unable to wait for finished task\n");
+            return -1;
+        }
+        free(s->task);
+        s->task = NULL;
+    }
+    return 0;
+#endif
+}
+
+
+int launch_task(AppState *s, FnJob f) {
+    debug("starting task thread...");
+#ifdef PICO
+    TaskHandle_t* task = malloc(sizeof(TaskHandle_t));
+    if (task == NULL) {
+        blink_failed(GPIOS[0]->pin, 300);
+    }
+
+    BaseType_t res =
+        xTaskCreate(f, "task", configMINIMAL_STACK_SIZE,
+                    NULL, configMAX_PRIORITIES - 1U, task);
+
+    if (res != pdPASS) {
+        printf("error: unable to launch run alarm task task, code error: %d\n",
+               res);
+        return -1;
+    }
+    s->task = task;
+#else
+    pthread_t* task = malloc(sizeof(task));
+    if (task == NULL) {
+        perror("error: unable to allocate memory for task thread");
+        return -1;
+    }
+
+    if (pthread_create(task, NULL, f, s) != 0) {
+        perror("error: thread task creation failed\n");
+        return -1;
+    }
+
+    s->task = task;
+#endif
+    return 0;
+}
+
+void check_btn_state(void* args) {
+    TaskParam* params = (TaskParam*) args;
+    AppState *s = params->s;
+    bool has_proceed = false;
+
+    for (;;) {
+        if (!gpio_get_input(GPIOS[1])) {
+#ifdef PICO
+            vTaskDelay(pdMS_TO_TICKS(BUTTON_BUFFETING_SLEEP_DURATION_MS));
+#else
+            _sleep_ms(BUTTON_BUFFETING_SLEEP_DURATION_MS);
+#endif
+            if(!gpio_get_input(GPIOS[1]) && !has_proceed) {
+                if (lock(s) != 0) {
+                    blink_failed(PICO_DEFAULT_LED_PIN, 200);
+                }
+
+                if (s->action == START) {
+                    s->action = STOP;
+                    cancel_task(s);
+                    if (release(s) != 0) {
+                        blink_failed(PICO_DEFAULT_LED_PIN, 200);
+                    }
+                    gpio_set_state(GPIOS[0], false);
+                    has_proceed = true;
+                    continue;
+                }
+
+                s->action = START;
+
+                if (launch_task(s, params->f) != 0) {
+                    blink_failed(PICO_DEFAULT_LED_PIN, 200);
+                }
+
+                if (release(s) != 0) {
+                    blink_failed(PICO_DEFAULT_LED_PIN, 200);
+                }
+
+                gpio_set_state(GPIOS[0], true);
+                has_proceed = true;
+            }
+            continue;
+        }
+        has_proceed = false;
+    }
+}
+
+#ifdef PICO
+void vApplicationStackOverflowHook(TaskHandle_t pxTask, char *pcTaskName) {
+    blink_failed(PICO_DEFAULT_LED_PIN, 200);
+}
+#endif
\ No newline at end of file
diff --git a/buzzer/jobs.h b/buzzer/jobs.h
new file mode 100644
index 0000000..00082cd
--- /dev/null
+++ b/buzzer/jobs.h
@@ -0,0 +1,47 @@
+//#define PICO
+
+#ifndef JOBS_H
+#define JOBS_H
+
+#ifdef PICO
+    #include "FreeRTOS.h"
+    #include "task.h"
+    #include "semphr.h"
+#else
+    #include <pthread.h>
+#endif
+
+typedef enum ACTION Action; 
+enum ACTION {STOP, START};
+
+typedef struct AppState AppState;
+struct AppState {
+    Action action;
+    
+    #ifdef PICO
+        TaskHandle_t* task;
+        SemaphoreHandle_t lock;
+    #else
+        pthread_mutex_t lock;
+        pthread_t* task;
+    #endif
+};
+
+typedef void (*FnJob)(void* params);
+
+typedef struct TaskParam TaskParam;
+struct TaskParam {
+    AppState* s;
+    FnJob f;  
+};
+
+int init_app_state(AppState *s);
+
+void check_btn_state(void* args);
+
+int lock(AppState *s);
+int release(AppState *s);
+int cancel_task(AppState *s);
+int launch_task(AppState *s, FnJob f);
+
+#endif
\ No newline at end of file
diff --git a/buzzer/log.c b/buzzer/log.c
new file mode 100644
index 0000000..610e6de
--- /dev/null
+++ b/buzzer/log.c
@@ -0,0 +1,28 @@
+#include <stdio.h>
+#include <stdarg.h>
+#include <time.h>
+
+#include "log.h"
+
+void debug(const char *format, ...) {
+#ifdef DEBUG
+    if (format == NULL) {
+        return;
+    }
+
+    time_t now;
+    time(&now);
+    char time_str[26];
+    ctime_r(&now, time_str);
+    time_str[24] = '\0';
+
+    fprintf(stdout, "[DEBUG] [%s] ", time_str);
+
+    va_list args;
+    va_start(args, format);
+    vfprintf(stdout, format, args);
+    va_end(args);
+
+    fprintf(stdout, "\n");
+#endif
+}
\ No newline at end of file
diff --git a/buzzer/log.h b/buzzer/log.h
new file mode 100644
index 0000000..dc06d79
--- /dev/null
+++ b/buzzer/log.h
@@ -0,0 +1,6 @@
+#ifndef LOG_H
+#define LOG_H
+
+void debug(const char *format, ...);
+
+#endif
\ No newline at end of file
diff --git a/buzzer/main.c b/buzzer/main.c
index 0c6dd2e..6bcfc66 100644
--- a/buzzer/main.c
+++ b/buzzer/main.c
@@ -1,45 +1,129 @@
+//#define PICO
+
+#ifdef PICO
 #include <pico/printf.h>
 #include <pico/stdlib.h>
-#include <hardware/pwm.h>
+#include "FreeRTOS.h"
+#include "task.h"
+#else
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <stdbool.h>
 
-#define GPIO_BUTTON 16
-#define GPIO_BUZZER 15
-#define NB_GPIO 2
+#define PICO_DEFAULT_LED_PIN 0
+#define GPIO_OUT 1
+#define GPIO_IN 0
+#endif
 
-typedef struct gpio gpio;
-struct gpio {
-    size_t pin;
-    size_t direction;
-};
+#include <math.h>
 
-static gpio GPIOS[2] = {
-    (gpio) {.pin = GPIO_BUZZER, .direction = GPIO_OUT},
-    (gpio) {
-        .pin = GPIO_BUTTON, .direction = GPIO_IN
+#include "log.h"
+#include "jobs.h"
+#include "gpio.h"
+
+#define ALARM_BASE_FREQ 2000 // auditive frequency human range: [20; 20000] hertz
+#define ALARM_PERIOD_MS 500
+#define PI 3.14
+
+/**
+ * Oscillator for passive buzzer hardware.
+ *
+ * It generates desired `freq_hz` for `duration_ms`.
+ *
+ * NOTE: `sleep_us` method does not impact FreeRTOS engine
+ * since, the scheduler started on two cores (RP2350). The behavior may differs
+ * on one core. Update the FreeRTOS tick freq and implement `pdUS_TO_TICKS` if needed.
+ */
+void gen_freq(gpio* g, size_t freq_hz, size_t duration_ms) {
+    if (!freq_hz) {
+        gpio_set_state(g, 0);
+        return;
     }
-};
 
-void init_gpio() {
-    gpio_init(PICO_DEFAULT_LED_PIN);
-    gpio_set_dir(PICO_DEFAULT_LED_PIN, GPIO_OUT);
+    float period = (1.0 / freq_hz) * 1000000; // signal period in micro seconds
+    size_t duty_period = period / 2; // working period = period / 2
+    size_t nb_period = duration_ms * 1000 / period; // number of period to play
 
-    for (size_t i = 0; i < NB_GPIO; i++) {
-        gpio_init(GPIOS[i].pin);
-        gpio_set_dir(GPIOS[i].pin, GPIOS[i].direction);
+    debug("freq_hz = (%ld), period_us = (%.2f), duty_period_us = (%ld), nb_period = (%ld)", freq_hz, period,
+          duty_period, nb_period);
+
+    for (size_t i = 0; i < nb_period; i++) {
+        gpio_set_state(g, true);
+        _sleep_us(duty_period);
+        gpio_set_state(g, false);
+        _sleep_us(duty_period);
     }
 }
 
+void run_alarm(void *const params) {
+    for(;;) {
+        debug("running alarm...");
+        float sin_val;
+        int tone_val;
+
+        const size_t duration_ms = ALARM_PERIOD_MS / 36;
+
+        for (size_t i = 0; i < 360; i+=10) {
+            sin_val = sinf(i * (PI / 180));
+            tone_val = ALARM_BASE_FREQ + sin_val * (ALARM_BASE_FREQ / 10);
+            gen_freq(GPIOS[2], tone_val, duration_ms);
+        }
+    }
+}
+
+/* Initialize the main FreeRTOS task */
+void init_rtos_main(TaskParam *params) {
+#ifdef PICO
+    BaseType_t res =
+        xTaskCreate(check_btn_state, "main", configMINIMAL_STACK_SIZE,
+                    (void *const)params, configMAX_PRIORITIES - 1U, NULL);
+
+    if (res != pdPASS) {
+        blink_failed(GPIOS[0]->pin, 500);
+    }
+#endif
+}
+
+/**
+ * A program to run alarm on button pushed.
+ *
+ * To activate the alarm, push the button. Same for desactivation.
+ * The alarm is launched in a separate task and controlled by
+ * the main task (which holds the push button logic).
+ *
+ * Hardware:
+ * - 1x Passive Buzzer
+ * - 1x Push button
+ * - 1 NPN transistor for signal amplification
+ * - 1x 1k ohm resistor (NPN collector)
+ * - 2x 10k ohm resistor
+ * 
+ * You can run the application in "DEBUG" mode using:
+ * `make run-debug name=buzzer`
+ * The FreeRTOS engine is replaced by threads.
+ */
 int main() {
-    stdio_init_all();
     init_gpio();
 
-    while (true) {
-        if (!gpio_get(GPIOS[1].pin)) {
-            gpio_put(PICO_DEFAULT_LED_PIN, true);
-            gpio_put(GPIOS[0].pin, true);
-            continue;
-        }
-        gpio_put(GPIOS[0].pin, false);
-        gpio_put(PICO_DEFAULT_LED_PIN, false);
-    }
+    AppState as;
+    init_app_state(&as);
+
+    TaskParam params = (TaskParam) {
+        .s = &as,
+        .f = run_alarm,
+    };
+
+#ifdef PICO
+    init_rtos_main(&params);
+#else
+    check_btn_state(&params);
+#endif
+
+#ifdef PICO
+    vTaskStartScheduler();
+#endif
+
+    blink_failed(PICO_DEFAULT_LED_PIN, 200);
 }