feat(vl53l1x): Add proximity alert example with buzzer. (#337)

* feat(vl53l1x): Add proximity alert example with buzzer.

* fix(vl53l1x): Address review comments on proximity alert example.

---------

Co-authored-by: Kaan Ozen <kaanozen@MacBook-Air-de-Kaan.local>

Author: Kaanoz-en

lib/vl53l1x/examples/proximity_alert.py

@@ -0,0 +1,45 @@
+"""Proximity alert using VL53L1X distance sensor and buzzer.
+
+Beeps the buzzer when an object is detected within 200 mm. The pitch
+increases as the object gets closer.
+"""
+
+from time import sleep_ms
+
+from machine import I2C, Pin
+from pyb import Timer
+from vl53l1x import VL53L1X
+
+DISTANCE_THRESHOLD_MM = 200
+
+# Sensor configuration
+i2c = I2C(1)
+tof = VL53L1X(i2c)
+
+# Buzzer initialisation
+buzzer_tim = Timer(1, freq=1000)
+buzzer_ch = buzzer_tim.channel(4, Timer.PWM, pin=Pin("SPEAKER"))
+buzzer_ch.pulse_width_percent(0)
+
+try:
+    while True:
+        distance = tof.read()
+        print("Distance: {} mm".format(distance))
+
+        if distance < DISTANCE_THRESHOLD_MM:
+            # Frequency ranging from 1500 (really close) to 500 (at 200mm)
+            freq = 1500 - (distance * 5)
+            # Security limits
+            freq = max(500, min(1500, freq))
+
+            buzzer_tim.freq(freq)
+            buzzer_ch.pulse_width_percent(50)
+        else:
+            buzzer_ch.pulse_width_percent(0)
+
+        sleep_ms(50)
+
+except KeyboardInterrupt:
+    pass
+finally:
+    buzzer_ch.pulse_width_percent(0)