|
| 1 | +""" |
| 2 | +mbed SDK |
| 3 | +Copyright (c) 2011-2013 ARM Limited |
| 4 | +SPDX-License-Identifier: Apache-2.0 |
| 5 | +
|
| 6 | +Licensed under the Apache License, Version 2.0 (the "License"); |
| 7 | +you may not use this file except in compliance with the License. |
| 8 | +You may obtain a copy of the License at |
| 9 | +
|
| 10 | + http://www.apache.org/licenses/LICENSE-2.0 |
| 11 | +
|
| 12 | +Unless required by applicable law or agreed to in writing, software |
| 13 | +distributed under the License is distributed on an "AS IS" BASIS, |
| 14 | +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 15 | +See the License for the specific language governing permissions and |
| 16 | +limitations under the License. |
| 17 | +""" |
| 18 | + |
| 19 | +from mbed_host_tests import BaseHostTest |
| 20 | +import time |
| 21 | + |
| 22 | + |
| 23 | +class TimingDriftSync(BaseHostTest): |
| 24 | + """ |
| 25 | + This works as master-slave fashion |
| 26 | + 1) Device says its booted up and ready to run the test, wait for host to respond |
| 27 | + 2) Host sends the message to get the device current time i.e base time |
| 28 | +
|
| 29 | + # |
| 30 | + # * |
| 31 | + # * | |
| 32 | + #<---* DUT<- base_time | - round_trip_base_time ------ |
| 33 | + # * | | |
| 34 | + # * - | |
| 35 | + # - | |
| 36 | + # | | |
| 37 | + # | | |
| 38 | + # | - measurement_stretch | - nominal_time |
| 39 | + # | | |
| 40 | + # | | |
| 41 | + # - | |
| 42 | + # * - | |
| 43 | + # * | | |
| 44 | + #<---* DUT <-final_time | - round_trip_final_time------ |
| 45 | + # * | |
| 46 | + # * - |
| 47 | + # |
| 48 | + # |
| 49 | + # As we increase the measurement_stretch, the error because of transport delay diminishes. |
| 50 | + # The values of measurement_stretch is propotional to round_trip_base_time(transport delays) |
| 51 | + # by factor time_measurement_multiplier.This multiplier is used is 80 to tolerate 2 sec of |
| 52 | + # transport delay and test time ~ 180 secs |
| 53 | + # |
| 54 | + # Failure in timing can occur if we are ticking too fast or we are ticking too slow, hence we have |
| 55 | + # min_range and max_range. if we cross on either side tests would be marked fail. The range is a function of |
| 56 | + # tolerance/acceptable drift currently its 5%. |
| 57 | + # |
| 58 | +
|
| 59 | + """ |
| 60 | + __result = None |
| 61 | + mega = 1000000.0 |
| 62 | + max_measurement_time = 180 |
| 63 | + |
| 64 | + # this value is obtained for measurements when there is 0 transport delay and we want accurancy of 5% |
| 65 | + time_measurement_multiplier = 80 |
| 66 | + |
| 67 | + def _callback_timing_drift_check_start(self, key, value, timestamp): |
| 68 | + self.round_trip_base_start = timestamp |
| 69 | + self.send_kv("base_time", 0) |
| 70 | + |
| 71 | + def _callback_base_time(self, key, value, timestamp): |
| 72 | + self.round_trip_base_end = timestamp |
| 73 | + self.device_time_base = float(value) |
| 74 | + self.round_trip_base_time = self.round_trip_base_end - self.round_trip_base_start |
| 75 | + |
| 76 | + self.log("Device base time {}".format(value)) |
| 77 | + measurement_stretch = (self.round_trip_base_time * self.time_measurement_multiplier) + 5 |
| 78 | + |
| 79 | + if measurement_stretch > self.max_measurement_time: |
| 80 | + self.log("Time required {} to determine device timer is too high due to transport delay, skipping".format(measurement_stretch)) |
| 81 | + else: |
| 82 | + self.log("sleeping for {} to measure drift accurately".format(measurement_stretch)) |
| 83 | + time.sleep(measurement_stretch) |
| 84 | + self.round_trip_final_start = time.time() |
| 85 | + self.send_kv("final_time", 0) |
| 86 | + |
| 87 | + def _callback_final_time(self, key, value, timestamp): |
| 88 | + self.round_trip_final_end = timestamp |
| 89 | + self.device_time_final = float(value) |
| 90 | + self.round_trip_final_time = self.round_trip_final_end - self.round_trip_final_start |
| 91 | + self.log("Device final time {} ".format(value)) |
| 92 | + |
| 93 | + # compute the test results and send to device |
| 94 | + results = "pass" if self.compute_parameter() else "fail" |
| 95 | + self.send_kv(results, "0") |
| 96 | + |
| 97 | + def setup(self): |
| 98 | + self.register_callback('timing_drift_check_start', self._callback_timing_drift_check_start) |
| 99 | + self.register_callback('base_time', self._callback_base_time) |
| 100 | + self.register_callback('final_time', self._callback_final_time) |
| 101 | + |
| 102 | + def compute_parameter(self, failure_criteria=0.05): |
| 103 | + t_max = self.round_trip_final_end - self.round_trip_base_start |
| 104 | + t_min = self.round_trip_final_start - self.round_trip_base_end |
| 105 | + t_max_hi = t_max * (1 + failure_criteria) |
| 106 | + t_max_lo = t_max * (1 - failure_criteria) |
| 107 | + t_min_hi = t_min * (1 + failure_criteria) |
| 108 | + t_min_lo = t_min * (1 - failure_criteria) |
| 109 | + device_time = (self.device_time_final - self.device_time_base) / self.mega |
| 110 | + |
| 111 | + self.log("Compute host events") |
| 112 | + self.log("Transport delay 0: {}".format(self.round_trip_base_time)) |
| 113 | + self.log("Transport delay 1: {}".format(self.round_trip_final_time)) |
| 114 | + self.log("DUT base time : {}".format(self.device_time_base)) |
| 115 | + self.log("DUT end time : {}".format(self.device_time_final)) |
| 116 | + |
| 117 | + self.log("min_pass : {} , max_pass : {} for {}%%".format(t_max_lo, t_min_hi, failure_criteria * 100)) |
| 118 | + self.log("min_inconclusive : {} , max_inconclusive : {}".format(t_min_lo, t_max_hi)) |
| 119 | + self.log("Time reported by device: {}".format(device_time)) |
| 120 | + |
| 121 | + if t_max_lo <= device_time <= t_min_hi: |
| 122 | + self.log("Test passed !!!") |
| 123 | + self.__result = True |
| 124 | + elif t_min_lo <= device_time <= t_max_hi: |
| 125 | + self.log("Test inconclusive due to transport delay, retrying") |
| 126 | + self.__result = False |
| 127 | + else: |
| 128 | + self.log("Time outside of passing range. Timing drift seems to be present !!!") |
| 129 | + self.__result = False |
| 130 | + return self.__result |
| 131 | + |
| 132 | + def result(self): |
| 133 | + return self.__result |
| 134 | + |
| 135 | + def teardown(self): |
| 136 | + pass |
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