Adding timing drift host test

TESTS/host_tests/timing_drift_auto.py

@@ -0,0 +1,106 @@
+"""
+mbed SDK
+Copyright (c) 2011-2013 ARM Limited
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+"""
+
+from mbed_host_tests import BaseHostTest
+
+
+class TimingDriftTest(BaseHostTest):
+    """ This test is reading single characters from stdio
+        and measures time between their occurrences.
+    """
+    __result = None
+    
+    # This is calculated later: average_drift_max * number of tick events
+    total_drift_max = None
+    
+    average_drift_max = 0.05
+    ticks = []
+    start_time = None
+    finish_time = None
+    dut_seconds_passed = None
+    total_time = None
+    total_drift = None
+    average_drift = None
+    
+    def _callback_result(self, key, value, timestamp):
+        # We should not see result data in this test
+        self.__result = False
+
+    def _callback_end(self, key, value, timestamp):
+        """ {{end;%s}}} """
+        self.log("Received end event, timestamp: %f" % timestamp)
+        self.notify_complete(result=self.result(print_stats=True))
+
+
+    def _callback_tick(self, key, value, timestamp):
+        """ {{tick;%d}}} """
+        self.log("tick! %f" % timestamp)
+        self.ticks.append((key, value, timestamp))
+
+
+    def setup(self):
+        self.register_callback("end", self._callback_end)
+        self.register_callback('tick', self._callback_tick)
+
+
+    def result(self, print_stats=True):        
+        self.dut_seconds_passed = len(self.ticks) - 1
+        
+        if self.dut_seconds_passed < 1:
+            if print_stats:
+                self.log("FAIL: failed to receive at least two tick events")
+            self.__result = False
+            return self.__result
+
+        self.total_drift_max = self.dut_seconds_passed * self.average_drift_max
+
+        self.start_time = self.ticks[0][2]
+        self.finish_time = self.ticks[-1][2]
+        self.total_time = self.finish_time - self.start_time
+        self.total_drift = self.total_time - self.dut_seconds_passed
+        self.average_drift = self.total_drift / self.dut_seconds_passed
+        
+        if print_stats:
+            self.log("Start: %f" % self.start_time)
+            self.log("Finish: %f" % self.finish_time)
+            self.log("Total time taken: %f" % self.total_time)
+        
+            total_drift_ratio_string = "Total drift/Max total drift: %f/%f"
+            self.log(total_drift_ratio_string % (self.total_drift,
+                                                 self.total_drift_max))
+                                                 
+            average_drift_ratio_string = "Average drift/Max average drift: %f/%f"
+            self.log(average_drift_ratio_string % (self.average_drift,
+                                                   self.average_drift_max))
+        
+
+        if self.total_drift > self.total_drift_max:
+            if print_stats:
+                self.log("FAIL: Total drift exceeded max total drift")
+            self.__result = False
+        elif self.average_drift > self.average_drift_max:
+            if print_stats:
+                self.log("FAIL: Average drift exceeded max average drift")
+            self.__result = False
+        else:
+            self.__result = True
+        
+        return self.__result
+
+
+    def teardown(self):
+        pass