features/unit/ultrasonic: GPIO interface ultrasonic distance sensor

Author: pandiannano

m5stack/libs/unit/ultrasonic_io.py

@@ -0,0 +1,45 @@
+# the sound speed on air (343.2 m/s), that It's equivalent to 0.34320 mm/us that is 1mm each 2.91us
+# pulse_time // 2 // 2.91 -> pulse_time // 5.82 -> pulse_time * 100 // 582
+# echo timeout -> max=4500mm, 4500 * 2.91us -> 0.0131 * 2 -> 0.0262 or 26.2ms
+# echo timeout -> 1000000us or 1s
+
+import machine
+from machine import Pin
+import utime
+
+class ULTRASONIC_IO:
+    def __init__(self, port, echo_timeout_us=1000000):
+        self.echo_timeout_us = echo_timeout_us
+        # trigger pin (out)
+        self.trigger = Pin(port[1], mode=Pin.OUT, pull=None)
+        self.trigger.value(0)
+        # echo pin (in)
+        self.echo = Pin(port[0], mode=Pin.IN, pull=None)
+
+    def tx_pulse_rx_echo(self):
+        
+        self.trigger.value(0) 
+        utime.sleep_us(5)
+        # Send a 10us pulse.
+        self.trigger.value(1)
+        utime.sleep_us(10)
+        self.trigger.value(0)
+        try:
+            echo_time = machine.time_pulse_us(self.echo, 1, self.echo_timeout_us)
+            return echo_time
+        except:
+            pass
+    
+    def get_target_distance(self, mode=1):
+        """
+        Get the distance in milimeters or centimeters.
+        """
+        echo_time = self.tx_pulse_rx_echo()
+        utime.sleep_ms(50)
+        if mode == 1:
+            mm = echo_time * 100 // 582
+            return mm
+        elif mode == 2:
+            cm = (echo_time * 100 // 582) / 10
+            return cm
+