bma421: Use the INT_STATUS register to distinguish between gestures

Currently we have only one type of hardware-based gesture implemented,
but in the future there could be more.

wasp/drivers/bma421.py

@@ -25,6 +25,9 @@ _DEFAULT_ORIENTATION = const(0b010010000)
 #          Y sign ────────────────────┘│
 #          Z sign ─────────────────────┘
 
+# Ref: BMA425 data sheet (register INT_STATUS_0)
+_STATUS_MASK_WRIST_TILT = const(0b1000)
+
 class BMA421:
     """BMA421 driver
 
@@ -82,8 +85,9 @@ class BMA421:
 
     def handle_interrupt(self, pin_obj):
         """Interrupt handler for gesture events originating from the sensor"""
-        self._dev.read_int_status() # TODO: Actually read status from the register
-        self._gesture_event = motion.AccelGestureEvent.WRIST_TILT
+        status = self._dev.read_int_status()
+        if status & _STATUS_MASK_WRIST_TILT:
+            self._gesture_event = motion.AccelGestureEvent.WRIST_TILT
 
     def get_gesture_event(self):
         """Receive the latest gesture event if any"""