add consumer control to hid_composite examples

both no OS and freeRTOS

examples/device/hid_composite/src/main.c

@@ -133,7 +133,7 @@ void hid_task(void)
       // no button, right + down, no scroll pan
       tud_hid_mouse_report(REPORT_ID_MOUSE, 0x00, delta, delta, 0, 0);
 
-      // delay a bit before attempt to send keyboard report
+      // delay a bit before sending keyboard report
       board_delay(10);
     }
   }
@@ -158,10 +158,34 @@ void hid_task(void)
       if (has_key) tud_hid_keyboard_report(REPORT_ID_KEYBOARD, 0, NULL);
       has_key = false;
     }
+
+    // delay a bit before sending consumer report
+    board_delay(10);
+  }
+
+  /*------------- Consume Control -------------*/
+  if ( tud_hid_ready() )
+  {
+    // use to avoid send multiple consecutive zero report
+    static bool has_consumer_key = false;
+
+    if ( btn )
+    {
+      // volume down
+      uint16_t volume_down = HID_USAGE_CONSUMER_VOLUME_DECREMENT;
+      tud_hid_report(REPORT_ID_CONSUMER_CONTROL, &volume_down, 2);
+
+      has_consumer_key = true;
+    }else
+    {
+      // send empty key report (release key) if previously has key pressed
+      uint16_t empty_key = 0;
+      if (has_consumer_key) tud_hid_report(REPORT_ID_CONSUMER_CONTROL, &empty_key, 2);
+      has_consumer_key = false;
+    }
   }
 }
 
-
 // Invoked when received GET_REPORT control request
 // Application must fill buffer report's content and return its length.
 // Return zero will cause the stack to STALL request