Set timer mode to Timer.PERIODIC explicitly

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: bradamiller

XRPLib/rangefinder.py

@@ -50,7 +50,7 @@ def __init__(self, trigger_pin: int|str = "RANGE_TRIGGER", echo_pin: int|str = "
         # Start a virtual timer to periodically send trigger pulses
         # 60ms period matches the HC-SR04 recommended minimum cycle time
         self._timer = Timer(-1)
-        self._timer.init(period=60, callback=self._trigger_ping)
+        self._timer.init(mode=Timer.PERIODIC, period=60, callback=self._trigger_ping)
 
     def _trigger_ping(self, t):
         """