samples/drivers: Provides basic sample for counter alarm

Provide basic sample to exercise counter alarm API.

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>

samples/drivers/counter/alarm/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.13.1)
+include($ENV{ZEPHYR_BASE}/cmake/app/boilerplate.cmake NO_POLICY_SCOPE)
+project(counter)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

samples/drivers/counter/alarm/README.rst

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+.. _alarm:
+
+counter alarm sample
+#####################
+
+Overview
+********
+This sample provides an example of alarm application using counter API.
+It sets an alarm with an initial delay of 2 seconds. At each alarm
+expiry, a new alarm is configured with a delay multiplied by 2.
+
+Requirements
+************
+
+This sample requires the support of a timer IP compatible with alarm setting.
+
+References
+**********
+
+- :ref:`disco_l475_iot1`
+
+Building and Running
+********************
+
+ .. zephyr-app-commands::
+    :zephyr-app: samples/counter/alarm
+    :host-os: unix
+    :board: disco_l475_iot1
+    :goals: run
+    :compact:
+
+Sample Output
+=============
+
+ .. code-block:: console
+
+    Counter alarm sample
+
+    Set alarm in 2 sec
+    !!! Alarm !!!
+    Now: 2
+    Set alarm in 4 sec
+    !!! Alarm !!!
+    Now: 6
+    Set alarm in 8 sec
+    !!! Alarm !!!
+    Now: 14
+    Set alarm in 16 sec
+    !!! Alarm !!!
+    Now: 30
+
+    <repeats endlessly>

samples/drivers/counter/alarm/prj.conf

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+CONFIG_PRINTK=y
+CONFIG_COUNTER=y

samples/drivers/counter/alarm/sample.yaml

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+sample:
+  name: Counter RTC Driver Sample
+tests:
+  test:
+    tags: drivers
+    harness: console
+    platform_whitelist: nucleo_f746zg
+    harness_config:
+        type: multi_line
+        ordered: true
+        regex:
+            - "Counter alarm sample"
+            -
+            - "Set alarm in 2 sec"
+            - "!!! Alarm !!!"
+            - "Now: 2"
+    depends_on: counter

samples/drivers/counter/alarm/src/main.c

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+/*
+ * Copyright (c) 2019 Linaro Limited
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr.h>
+
+#include <device.h>
+#include <counter.h>
+#include <misc/printk.h>
+
+#define DELAY 2000000
+#define ALARM_CHANNEL_ID 0
+
+struct counter_alarm_cfg alarm_cfg;
+
+static void test_counter_interrupt_fn(struct device *counter_dev,
+				u8_t chan_id, u32_t ticks, void *user_data)
+{
+	u32_t now_ticks = counter_read(counter_dev);
+	u64_t now_usec = counter_ticks_to_us(counter_dev, now_ticks);
+	int now_sec = (int)(now_usec / USEC_PER_SEC);
+	struct counter_alarm_cfg *config = user_data;
+
+	printk("!!! Alarm !!!\n");
+	printk("Now: %d\n", now_sec);
+
+	/* Set a new alarm with a double lenght duration */
+	config->ticks = 2 * config->ticks;
+
+	printk("Set alarm in %d sec\n", config->ticks);
+	counter_set_channel_alarm(counter_dev, ALARM_CHANNEL_ID, user_data);
+}
+
+void main(void)
+{
+	struct device *counter_dev;
+	int err = 0;
+
+	printk("Counter alarm sample\n\n");
+	counter_dev = device_get_binding(DT_RTC_0_NAME);
+
+	counter_start(counter_dev);
+
+	alarm_cfg.absolute = false;
+	alarm_cfg.ticks = counter_us_to_ticks(counter_dev, DELAY);
+	alarm_cfg.callback = test_counter_interrupt_fn;
+	alarm_cfg.user_data = &alarm_cfg;
+
+	err = counter_set_channel_alarm(counter_dev, ALARM_CHANNEL_ID,
+					&alarm_cfg);
+	printk("Set alarm in %d sec\n", alarm_cfg.ticks);
+
+	if (-EINVAL == err) {
+		printk("Alarm settings invalid\n");
+	} else if (-ENOTSUP == err) {
+		printk("Alarm setting request not supported\n");
+	} else if (err != 0) {
+		printk("Error\n");
+	}
+
+	while (1) {
+		k_sleep(K_FOREVER);
+	}
+}