Add wait_ns timing test

Author: kjbracey

TESTS/mbed_platform/wait_ns/main.cpp

@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2018, ARM Limited, All Rights Reserved
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * 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.
+ */
+
+#include "mbed.h"
+#include "greentea-client/test_env.h"
+#include "unity.h"
+#include "utest.h"
+#include "platform/mbed_wait_api.h"
+#include "hal/us_ticker_api.h"
+#include "hal/lp_ticker_api.h"
+
+using namespace utest::v1;
+
+/* This test is created based on the test for Timer class.
+ * Since low power timer is less accurate than regular
+ * timer we need to adjust delta.
+ */
+
+/*
+* Define tolerance as follows:
+* Timer might be +/-5% out; wait_ns is permitted 20% slow, but not fast.
+* Therefore minimum measured time should be 95% of requested, maximum should
+* be 125%. Unity doesn't let us specify an asymmetric error though.
+*/
+#define TOLERANCE_MIN 0.95f
+#define TOLERANCE_MAX 1.25f
+#define MIDPOINT ((TOLERANCE_MIN+TOLERANCE_MAX)/2)
+#define DELTA (MIDPOINT-TOLERANCE_MIN)
+
+/* This test verifies if wait_ns's wait time
+ * is accurate, according to a timer.
+ *
+ * Given timer is created.
+ * When timer is used to measure delay.
+ * Then the results are valid (within acceptable range).
+ */
+template<int wait_val_ms, class CompareTimer>
+void test_wait_ns_time_measurement()
+{
+    CompareTimer timer;
+
+    float wait_val_s = (float)wait_val_ms / 1000;
+
+    /* Start the timer. */
+    timer.start();
+
+    /* Wait <wait_val_ms> ms - arithmetic inside wait_ns will overflow if
+     * asked for too large a delay, so break it up.
+     */
+    for (int i = 0; i < wait_val_ms; i++) {
+        wait_ns(1000000);
+    }
+
+    /* Stop the timer. */
+    timer.stop();
+
+    /* Check results - wait_val_us us have elapsed. */
+    TEST_ASSERT_FLOAT_WITHIN(DELTA * wait_val_s, MIDPOINT * wait_val_s, timer.read());
+}
+
+utest::v1::status_t test_setup(const size_t number_of_cases)
+{
+    GREENTEA_SETUP(15, "default_auto");
+    return verbose_test_setup_handler(number_of_cases);
+}
+
+Case cases[] = {
+#if DEVICE_LPTICKER
+    Case("Test: wait_ns - compare with lp_timer 1s", test_wait_ns_time_measurement<1000, LowPowerTimer>),
+#endif
+    Case("Test: wait_ns - compare with us_timer 1s", test_wait_ns_time_measurement<1000, Timer>)
+};
+
+Specification specification(test_setup, cases);
+
+int main()
+{
+    return !Harness::run(specification);
+}