diff --git a/init.c b/init.c
index 3e0c078..613bf58 100644
--- a/init.c
+++ b/init.c
@@ -11,6 +11,7 @@ void init_gpios(void)
 	gpio_enable(GPIOC);
 
 	gpio_set_mode(GPIOC, BIT8 | BIT9 | BIT7, MODER_OUTPUT);
+	gpio_set_mode(GPIOA, BIT0, MODER_INPUT);
 }
 
 
diff --git a/main.c b/main.c
index ce248ed..6310a63 100644
--- a/main.c
+++ b/main.c
@@ -5,12 +5,36 @@
 
 #include "init.h"
 
-
-void blink(void) {
+void blink_green(void)
+{
 	GPIOC_ODR ^= BIT9;
 }
 
 
+// --- async delayed blue blink ---
+
+bool blue_blink_pending = false;
+
+void blue_off(void)
+{
+	GPIOC_ODR &= ~BIT8;
+	blue_blink_pending = false;
+}
+
+void blink_blue(void)
+{
+	GPIOC_ODR |= BIT8;
+	register_future_task(blue_off, 200);
+}
+
+
+// called every 1s
+
+void say_hello(void)
+{
+	usart_tx_string(USART3, "HELLO\r\n");
+}
+
 
 /** Called before main() */
 void SystemInit(void)
@@ -20,16 +44,25 @@ void SystemInit(void)
 	init_gpios();
 	init_usart();
 
-	schedule_timed_task(blink, 500);
+	register_periodic_task(blink_green, 500);
+	register_periodic_task(say_hello, 1000);
 }
 
 
 int main(void)
 {
+	int btn_c = 0;
 	while (1) {
-		delay_ms(1000);
-		GPIOC_ODR ^= BIT8;
+		bool btn = GPIOA_IDR & BIT0;
+		if (btn) {
+			if (btn_c++ > 20 && !blue_blink_pending) {
+				blue_blink_pending = true;
+				register_future_task(blink_blue, 1000);
+			}
+		} else {
+			btn_c = 0;
+		}
 
-		usart_tx_string(USART3, "HELLO\r\n");
+		delay_ms(1);
 	}
 }
diff --git a/utils/timebase.c b/utils/timebase.c
index 5aa100a..661b2e3 100644
--- a/utils/timebase.c
+++ b/utils/timebase.c
@@ -2,28 +2,43 @@
 
 volatile uint32_t TIME_MS;
 
-#define TASK_COUNT 10
+#define PERIODIC_TASK_COUNT 5
+#define FUTURE_TASK_COUNT 5
 
 // --- time scheduler system ---
 typedef struct {
 	/** User callback */
-	void (*callback) (void);
+	void (*callback)(void);
 	/** Callback interval */
 	uint32_t interval_ms;
 	/** Counter, when reaches interval_ms, is cleared and callback is called. */
 	uint32_t countup;
-} timebase_cb_t;
+} periodic_task_t;
 
-static uint8_t scheduled_task_n = 0;
-static timebase_cb_t scheduled_tasks[TASK_COUNT];
+static uint8_t periodic_task_n = 0;
+static periodic_task_t periodic_tasks[PERIODIC_TASK_COUNT];
 
 
-bool schedule_timed_task(void (*callback) (void), uint32_t interval_ms)
+// --- future call system ---
+typedef struct {
+	/** 1 for active tasks */
+	bool active;
+	/** User callback */
+	void (*callback)(void);
+	/** Counter, when reaches 0ms, callback is called and the task is removed */
+	uint32_t countdown_ms;
+} future_task_t;
+
+static future_task_t future_tasks[FUTURE_TASK_COUNT];
+
+
+
+bool register_periodic_task(void (*callback)(void), uint32_t interval_ms)
 {
-	if (scheduled_task_n >= TASK_COUNT) return false;
+	if (periodic_task_n >= PERIODIC_TASK_COUNT) return false;
 
 	// add the task
-	timebase_cb_t *task = &scheduled_tasks[scheduled_task_n++];
+	periodic_task_t *task = &periodic_tasks[periodic_task_n++];
 	task->callback = callback;
 	task->countup = 0;
 	task->interval_ms = interval_ms;
@@ -32,19 +47,47 @@ bool schedule_timed_task(void (*callback) (void), uint32_t interval_ms)
 }
 
 
+
+bool register_future_task(void (*callback)(void), uint32_t delay_ms)
+{
+	for (int i = 0; i < FUTURE_TASK_COUNT; i++) {
+		future_task_t *task = &future_tasks[i];
+		if (task->active) continue;
+
+		task->callback = callback;
+		task->countdown_ms = delay_ms;
+		task->active = true;
+	}
+
+	return false;
+}
+
+
+
 /** IRQ */
 void SysTick_Handler(void)
 {
 	TIME_MS++;
 
 	// run scheduled tasks
-	for (int i = 0; i < scheduled_task_n; i++) {
-		timebase_cb_t *task = &scheduled_tasks[i];
+	for (int i = 0; i < periodic_task_n; i++) {
+		periodic_task_t *task = &periodic_tasks[i];
 		if (task->countup++ >= task->interval_ms) {
 			task->callback();
 			task->countup = 0;
 		}
 	}
+
+	// run future tasks
+	for (int i = 0; i < FUTURE_TASK_COUNT; i++) {
+		future_task_t *task = &future_tasks[i];
+		if (!task->active) continue;
+
+		if (task->countdown_ms-- == 0) {
+			task->callback();
+			task->active = 0;
+		}
+	}
 }
 
 
diff --git a/utils/timebase.h b/utils/timebase.h
index 4a2fee5..833e4e5 100644
--- a/utils/timebase.h
+++ b/utils/timebase.h
@@ -6,5 +6,8 @@ extern volatile uint32_t TIME_MS;
 void delay_ms(uint32_t ms);
 void delay_s(uint32_t s);
 
-/** Schedule a timed task (like a cron job) */
-bool schedule_timed_task(void (*callback) (void), uint32_t interval_ms);
+/** Schedule a periodic task (like a cron job). Returns success. */
+bool register_periodic_task(void (*callback) (void), uint32_t interval_ms);
+
+/** Schedule a future one-off task. Returns success. */
+bool register_future_task(void (*callback)(void), uint32_t delay_ms);