diff --git a/libraries/AP_HAL/GPIO.h b/libraries/AP_HAL/GPIO.h
index 742076d7ed..48ca9eca4b 100644
--- a/libraries/AP_HAL/GPIO.h
+++ b/libraries/AP_HAL/GPIO.h
@@ -73,4 +73,7 @@ public:
 
     /* return true if USB cable is connected */
     virtual bool    usb_connected(void) = 0;
+
+    // optional timer tick
+    virtual void timer_tick(void) {};
 };