px4_uploader: Prevent spin-lock from hogging CPU

Tools/px_uploader.py

@@ -501,7 +501,8 @@ print("Loaded firmware for %x,%x, size: %d bytes, waiting for the bootloader..."
 print("If the board does not respond within 1-2 seconds, unplug and re-plug the USB connector.")
 
 # Spin waiting for a device to show up
-while True:
+try:
+    while True:
             portlist = []
             patterns = args.port.split(",")
             # on unix-like platforms use glob to support wildcard ports. This allows
@@ -573,3 +574,11 @@ while True:
 
                     # we could loop here if we wanted to wait for more boards...
                     sys.exit(0)
+
+            #Rate-limit retries to prevent spin-lock from hogging the CPU
+            time.sleep(0.5)
+
+#CTRL+C aborts the upload/spin-lock by interrupt mechanics            
+except KeyboardInterrupt:
+    print("\n Upload aborted by user.")
+    sys.exit(0)