samples: sensor: sm351lt: Add new SM351LT sensor sample

Adds sample for SM351LT sensor and outputs to console.

Signed-off-by: Jamie McCrae <jamie.mccrae@lairdconnect.com>

samples/sensor/sm351lt/CMakeLists.txt

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+#
+# Copyright (c) 2020, Laird Connectivity
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+cmake_minimum_required(VERSION 3.13.1)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(sm351lt)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

samples/sensor/sm351lt/README.rst

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+.. _sm351lt:
+
+SM351LT: Magnetoresistive Sensor Example
+########################################
+
+Overview
+********
+
+This sample application periodically polls an SM351LT magnetoresistive sensor
+and displays if a magnet near to the sensor, via the console.
+
+Requirements
+************
+
+This sample uses the Honeywell SM351LT sensor.
+
+References
+**********
+
+For more information about the SM351LT magnetoresistive sensor see
+https://sensing.honeywell.com/SM351LT-low-power
+
+Building and Running
+********************
+
+The SM351LT (or compatible) sensors are available on the following boards:
+
+* :ref:`bt510`
+
+Building on bt510
+==================
+
+:ref:`bt510` includes a Honeywell SM351LT magnetoresistive sensor.
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/sensor/sm351lt
+   :board: bt510
+   :goals: build flash
+   :compact:
+
+Sample Output
+=============
+
+.. code-block:: console
+
+    Polling at 0.5 Hz
+    #1 @ 6 ms: 1
+    #2 @ 2007 ms: 0
+    #3 @ 4009 ms: 0
+    #4 @ 6010 ms: 1
+    #5 @ 8012 ms: 1

samples/sensor/sm351lt/prj.conf

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+CONFIG_STDOUT_CONSOLE=y
+CONFIG_GPIO=y
+CONFIG_SENSOR=y
+CONFIG_SM351LT=y

samples/sensor/sm351lt/sample.yaml

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+sample:
+  name: SM351LT Magnetoresistive Sensor Example
+tests:
+  sample.sensor.sm351lt:
+    harness: sensor
+    tags: samples sensor
+    depends_on: gpio sm351lt

samples/sensor/sm351lt/src/main.c

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+/*
+ * Copyright (c) 2020 Laird Connectivity
+ * Based on code by Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stdio.h>
+#include <zephyr.h>
+#include <device.h>
+#include <drivers/gpio.h>
+#include <drivers/sensor.h>
+
+static void fetch_and_display(struct device *sensor)
+{
+	static unsigned int count;
+	struct sensor_value mag;
+	int rc = sensor_sample_fetch(sensor);
+
+	++count;
+	if (rc == 0) {
+		rc = sensor_channel_get(sensor,
+					SENSOR_CHAN_PROX,
+					&mag);
+	}
+	if (rc < 0) {
+		printf("ERROR: Update failed: %d\n", rc);
+	} else {
+		printf("#%u @ %u ms: %d\n",
+		       count, k_uptime_get_32(), mag.val1);
+	}
+}
+
+#ifdef CONFIG_SM351LT_TRIGGER
+static void trigger_handler(struct device *dev,
+			    struct sensor_trigger *trig)
+{
+	fetch_and_display(dev);
+}
+#endif
+
+void main(void)
+{
+	struct device *sensor = device_get_binding(DT_LABEL(DT_INST(0, honeywell_sm351lt)));
+
+	if (sensor == NULL) {
+		printf("Could not get %s device\n",
+		       DT_LABEL(DT_INST(0, honeywell_sm351lt)));
+		return;
+	}
+
+#if CONFIG_SM351LT_TRIGGER
+	{
+		struct sensor_trigger trig;
+		int rc;
+
+		trig.type = SENSOR_TRIG_NEAR_FAR;
+		trig.chan = SENSOR_CHAN_PROX;
+
+		struct sensor_value trigger_type = {
+			.val1 = GPIO_INT_EDGE_BOTH,
+		};
+
+		rc = sensor_attr_set(sensor, trig.chan,
+				     SENSOR_ATTR_PRIV_START,
+				     &trigger_type);
+		if (rc != 0) {
+			printf("Failed to set trigger type: %d\n", rc);
+			return;
+		}
+
+		rc = sensor_trigger_set(sensor, &trig, trigger_handler);
+		if (rc != 0) {
+			printf("Failed to set trigger: %d\n", rc);
+			return;
+		}
+
+		printf("Waiting for triggers\n");
+		while (true) {
+			k_sleep(K_MSEC(2000));
+		}
+	}
+#else /* CONFIG_SM351LT_TRIGGER */
+	printf("Polling at 0.5 Hz\n");
+	while (true) {
+		fetch_and_display(sensor);
+		k_sleep(K_MSEC(2000));
+	}
+#endif /* CONFIG_SM351LT_TRIGGER */
+}