samples: Add max30101 sample application

Adds a max30101 sample application that polls sensor data and prints it
to the console.

Jira: ZEP-720
Change-Id: I50f28eaf9ea2ff5bfbb9fb6922c4006d5c02e739
Signed-off-by: Maureen Helm <maureen.helm@nxp.com>

samples/sensor/max30101/Makefile

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+# Makefile - max30101 sample
+#
+# Copyright (c) 2017, NXP
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+BOARD ?= hexiwear_k64
+CONF_FILE ?= prj.conf
+
+include $(ZEPHYR_BASE)/Makefile.inc

samples/sensor/max30101/README.rst

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+.. _max30101:
+
+MAX30101 Heart Rate Sensor
+##########################
+
+Overview
+********
+
+A sensor application that demonstrates how to poll data from the max30101 heart
+rate sensor.
+
+Building and Running
+********************
+
+This project configures the max30101 sensor on the :ref:`hexiwear_k64` board to
+enable the green LED and measure the reflected light with a photodiode. The raw
+ADC data prints to the console. Further processing (not included in this
+sample) is required to extract a heart rate signal from the light measurement.
+
+.. code-block:: console
+
+   $ cd samples/sensors/max30101
+   $ make BOARD=hexiwear_k64
+
+Sample Output
+=============
+
+.. code-block:: console
+
+   GREEN=5731
+   GREEN=5750
+   GREEN=5748
+   GREEN=5741
+   GREEN=5735
+   GREEN=5737
+   GREEN=5736
+   GREEN=5748
+
+<repeats endlessly>

samples/sensor/max30101/prj.conf

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+CONFIG_STDOUT_CONSOLE=y
+CONFIG_SYS_LOG=y
+CONFIG_I2C=y
+CONFIG_SENSOR=y
+CONFIG_SYS_LOG_SENSOR_LEVEL=4
+CONFIG_MAX30101=y

samples/sensor/max30101/src/Makefile

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+# Makefile - max30101 sample
+#
+# Copyright (c) 2017, NXP
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+obj-y = main.o

samples/sensor/max30101/src/main.c

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+/*
+ * Copyright (c) 2017, NXP
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr.h>
+#include <sensor.h>
+#include <stdio.h>
+
+void main(void)
+{
+	struct sensor_value green;
+	struct device *dev = device_get_binding(CONFIG_MAX30101_NAME);
+
+	if (dev == NULL) {
+		printf("Could not get max30101 device\n");
+		return;
+	}
+
+	while (1) {
+		sensor_sample_fetch(dev);
+		sensor_channel_get(dev, SENSOR_CHAN_GREEN, &green);
+
+		/* Print green LED data*/
+		printf("GREEN=%d\n", green.val1);
+
+		k_sleep(20);
+	}
+}

samples/sensor/max30101/testcase.ini

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+[test]
+build_only = true
+tags = samples sensor
+platform_whitelist = hexiwear_k64