Implement heartbeat using SWTimer

src/main_osp.cc

@@ -217,6 +217,13 @@ namespace Heck {
         bool heartbeat_led_state{ false };
         u32 heartbeat_systick_last{};
 
+        SWTimer heartbeat{};
+        heartbeat.set_period(500);
+        heartbeat.set_callback([&heartbeat_led_state](){
+            heartbeat_led_state = !heartbeat_led_state;
+            hw.SetLed(heartbeat_led_state);
+        });
+
         bool but_record_new{ false };
         bool but_record_current{ false };
 
@@ -340,12 +347,7 @@ namespace Heck {
                     }
                 }
             }
-
-            if (systick_now - heartbeat_systick_last > 500) {
-                heartbeat_systick_last = systick_now;
-                heartbeat_led_state = !heartbeat_led_state;
-                hw.SetLed(heartbeat_led_state);
-            }
+            heartbeat.is_it_already_time_again(systick_now);
         }
     }
 } // namespace Heck