1328 · February 1, 2016 16:38 · Feb 1, 2016
diff --git a/x.py b/x.py
@@ -0,0 +1,78 @@
+
+import time
+
+# create a dictionary 
+state = {
+        'start': time.time(),
+        'countdown': 5,
+        'clock': 5,
+        'ok': True,
+        'boosters': 'off',
+        }
+
+
+def poll(state):
+    '''
+    this would probably just check the clock on the audrino
+    but for now we mock it up using time.time
+    '''
+
+    running = time.time() - state['start']
+    state['clock'] = int(state['countdown'] - running)
+
+# now define a bunch of functions to be called at various times on the countdown
+# each function gets passed the state dictionary and can modify that dictionary
+# (sicne dictionaries are mutable) to pass information to other parts of the
+# code
+
+def do_systems_check(state):
+    if state['ok']:
+        print('all systems go')
+
+def do_boosters(state):
+    if state['ok']:
+        state['boosters'] = 'on'
+        print('boosters on')
+
+def do_lift_off(state):
+    if state['ok'] and state['boosters'] == 'on':
+        print('lift off')
+
+# now we put all of those do_ functions into a dictionary, with keys that
+# identify when they should be called, thus:  at T-4 we do a systems check, at 
+
+
+EVENTS = {
+        4:do_systems_check,
+        2:do_boosters,
+        0:do_lift_off,
+        }
+
+last_clock = None # to prevent duplicates
+while state['clock']>0:
+    poll(state)
+    clock = state['clock']
+    if clock == last_clock:
+        # the clock has not meaningfully changed, so just sleep and wait for
+        # poll to return something interesting
+        # the logic will need to be extended to allow for other events to
+        # wake-up the logic, other than just the clock rolling over
+        # also, consider doing away with the sleep, as it will cause a bit of a
+        # lag
+
+        time.sleep(.1)
+        continue
+    last_clock = clock
+
+    print('T minus {}'.format(state['clock']))
+
+    # now check the events dictionary to see if we trigger anything
+
+    if clock in EVENTS:
+        func = EVENTS[clock]
+        func(state)
+
+
+
+
+