Add threaded dual stepper example

Author: caternuson

examples/DualStepperTest.py

@@ -0,0 +1,63 @@
+#!/usr/bin/python
+#
+# NOTE - Only for use on Raspberry Pi or other SBC.
+#
+import time
+import atexit
+import threading
+import random
+from adafruit_motorkit import MotorKit
+from adafruit_motor import stepper as STEPPER
+
+# create a default object, no changes to I2C address or frequency
+kit = MotorKit()
+
+# create empty threads (these will hold the stepper 1 and 2 threads)
+st1 = threading.Thread()
+st2 = threading.Thread()
+
+# recommended for auto-disabling motors on shutdown!
+def turnOffMotors():
+    kit.stepper1.release()
+    kit.stepper2.release()
+
+atexit.register(turnOffMotors)
+
+stepstyles = [STEPPER.SINGLE, STEPPER.DOUBLE, STEPPER.INTERLEAVE, STEPPER.MICROSTEP]
+
+def stepper_worker(stepper, numsteps, direction, style):
+    #print("Steppin!")
+    for _ in range(numsteps):
+        stepper.onestep(direction=direction, style=style)
+    #print("Done")
+
+while (True):
+    if not st1.isAlive():
+        randomdir = random.randint(0, 1)
+        print("Stepper 1"),
+        if (randomdir == 0):
+            dir = STEPPER.FORWARD
+            print("forward"),
+        else:
+            dir = STEPPER.BACKWARD
+            print("backward"),
+        randomsteps = random.randint(10,50)
+        print("%d steps" % randomsteps)
+        st1 = threading.Thread(target=stepper_worker, args=(kit.stepper1, randomsteps, dir, stepstyles[random.randint(0,3)],))
+        st1.start()
+
+    if not st2.isAlive():
+        print("Stepper 2"),
+        randomdir = random.randint(0, 1)
+        if (randomdir == 0):
+            dir = STEPPER.FORWARD
+            print("forward"),
+        else:
+            dir = STEPPER.BACKWARD
+            print("backward"),
+        randomsteps = random.randint(10,50)
+        print("%d steps" % randomsteps)
+        st2 = threading.Thread(target=stepper_worker, args=(kit.stepper2, randomsteps, dir, stepstyles[random.randint(0,3)],))
+        st2.start()
+
+    time.sleep(0.1) # Small delay to stop from constantly polling threads (see: https://forums.adafruit.com/viewtopic.php?f=50&t=104354&p=562733#p562733)