additional sensor module with ultrasonic sensor HC-SR04

Author: a-tom-s

pi_mqtt_gpio/modules/hcsr04.py

@@ -0,0 +1,83 @@
+from pi_mqtt_gpio.modules import GenericSensor
+import time
+import datetime
+
+REQUIREMENTS = ("RPi.GPIO",)
+
+# HC-SR04 ultrasonic sensor_inputs
+# for use at Raspberry Pi, the ECHO signal of the sensor must be reduced to 3.3V, since the sensor works with 5V!!
+# You can simply reduce with a 3.9kOhm and 6.8kOhm resistor voltage reduction
+#
+# further information at http://www.netzmafia.de/skripten/hardware/RasPi/Projekt-Ultraschall/
+# The code is based on the sample code of this webpage by Prof.Plate / University of Munich
+
+CONFIG_SCHEMA = {
+    "pin_echo": {"type": "integer", "required": True, "empty": False},
+    "pin_trigger": {"type": "integer", "required": True, "empty": False},
+    "burst": {"type": "integer", "required": True, "empty": False},
+}
+# duration trigger pulse
+PULSE = 0.00001
+# sonic speed/2
+SPEED_2 = 17015
+
+class Sensor(GenericSensor):
+
+    def __init__(self, config):
+        import RPi.GPIO as GPIO
+
+        self.gpio = GPIO
+        self.pin_Trigger = config["pin_trigger"]
+        self.pin_Echo = config["pin_echo"]
+        self.burst = config["burst"]
+
+    def setup_sensor(self, config):
+        # use BCM GPIO-references (instead of Pin-numbers)
+        # and define GPIO-input/output
+        self.gpio.setmode(self.gpio.BCM)
+        self.gpio.setup(self.pin_Trigger,self.gpio.OUT)
+        self.gpio.setup(self.pin_Echo,self.gpio.IN)
+        self.gpio.remove_event_detect(self.pin_Echo)
+        self.gpio.output(self.pin_Trigger, False)
+        time.sleep(1)                           # Setup-time for Sensor
+        self.gpio.add_event_detect(self.pin_Echo, self.gpio.BOTH, callback=self.measure)    # create callback triggered by rising and falling edge
+
+        self.stopp = 0
+        self.start = 0
+        self.distance = 0
+
+        return True
+
+    def get_value(self, config):
+        value = self.measure_range()
+        return value
+
+    def pulse(self):                            # function to start measurement
+      self.gpio.output(self.pin_Trigger, True)  # create trigger pulse
+      time.sleep(PULSE)
+      self.gpio.output(self.pin_Trigger, False)
+      self.stopp = 0
+      self.start = 0
+      self.distance = 0
+
+    def measure(self, x):                       # Callback-Function for echo signal
+      if self.gpio.input(self.pin_Echo) == 1:   # save time of rising echo signal
+        self.start = time.time()
+      else:                                     # falling edge, save time
+        self.stopp = time.time()
+        delta = self.stopp - self.start         # calculate time difference sending / receiving
+        self.distance = delta * SPEED_2         # calculate distance by time and sonic speed
+
+    def measure_range(self):                    # start measures and calculate average of BURST measurements
+      values = []
+      sum = 0
+      for i in range(0, self.burst):
+        self.pulse()                            # start measurement
+        time.sleep(0.040)                       # wait till end of measurement
+        values.append(self.distance)            # save value in array and sum up
+        sum = sum + values[i]
+        time.sleep(0.05)
+      return sum/self.burst;                         # return average
+
+    def cleanup(self):
+        self.gpio.cleanup()