R3PTAR demo

Author: ddemidov

demo/R3PTAR/README.md

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+R3PTAR
+======
+
+One of the most loved robots, the standing 35 cm. / 13,8 inch tall R3PTAR robot
+slithers across the floor like a real cobra, and strikes at lightning speed
+with it’s pointed red fangs.
+
+Coincidentally, its also a nice example to demonstrate how to use threads in
+Python.
+
+**Building instructions**: http://www.lego.com/en-us/mindstorms/build-a-robot/r3ptar
+
+**Resources**:
+
+* `rattle-snake.wav`: https://www.freesound.org/people/7h3_lark/sounds/268580/
+* `snake-hiss.wav`: https://www.freesound.org/people/Reitanna/sounds/343928/

demo/R3PTAR/r3ptar.py

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+#!/usr/bin/env python3
+
+import time
+import threading
+import ev3dev.ev3 as ev3
+
+def tail_waggler():
+    """
+    This is the first thread of execution that will be responsible for waggling
+    r3ptar's tail every couple of seconds.
+    """
+    m = ev3.MediumMotor(); assert m.connected
+
+    while True:
+        m.run_timed(speed_sp=90, time_sp=1000, stop_action='coast')
+        time.sleep(1)
+        ev3.Sound.play('rattle-snake.wav').wait()
+        m.run_timed(speed_sp=-90, time_sp=1000, stop_action='coast')
+        time.sleep(2)
+
+def hand_biter():
+    """
+    This is the second thread of execution. It will constantly poll the
+    infrared sensor for proximity info and bite anything that gets too close.
+    """
+    m = ev3.LargeMotor('outD'); assert m.connected
+    s = ev3.InfraredSensor();   assert s.connected
+
+    m.run_timed(speed_sp=-200, time_sp=1000, stop_action='brake')
+
+    while True:
+        # Wait until something (a hand?!) gets too close:
+        while s.proximity() > 30: time.sleep(0.1)
+
+        # Bite it! Also, don't forget to hiss:
+        ev3.Sound.play('snake-hiss.wav')
+        m.run_timed(speed_sp=600, time_sp=500, stop_action='brake')
+        time.sleep(0.6)
+        m.run_timed(speed_sp=-200, time_sp=500, stop_action='brake')
+        time.sleep(1)
+
+
+# Now that we have the worker functions defined, lets start them both in
+# separate threads.
+# Actually, we could run just one of those in a separate thread, and call the
+# other from our own (master) thread, but this way seems to be more symmetric:
+threading.Thread(target=tail_waggler).start()
+threading.Thread(target=hand_biter).start()