samples: sensor: adt7420: Add ADT7420 sample application

This simple application periodically prints the ambient temperature.
Optional support for threshold triggers is provided.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>

samples/sensor/adt7420/CMakeLists.txt

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+include($ENV{ZEPHYR_BASE}/cmake/app/boilerplate.cmake NO_POLICY_SCOPE)
+project(NONE)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

samples/sensor/adt7420/README.rst

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+.. _adt7420:
+
+ADT7420: High accuracy digital I2C temperature sensor
+#####################################################
+
+Description
+***********
+
+This sample application periodically (1Hz) measures the ambient temperature
+in degrees Celsius. The result is written to the console.
+Optionally, it also shows how to use the upper and lower threshold triggers.
+
+References
+**********
+
+ - ADT7420: http://www.analog.com/adt7420
+
+Wiring
+*******
+
+This sample uses the ADT7420 sensor controlled using the I2C interface.
+Connect Supply: **VDD**, **GND** and Interface: **SDA**, **SCL**
+and optionally connect the **INT** to a interrupt capable GPIO.
+The supply voltage can be in the 2.7V to 5.5V range.
+Depending on the baseboard used, the **SDA** and **SCL** lines require Pull-Up
+resistors.
+
+Building and Running
+********************
+
+This project outputs sensor data to the console. It requires an ADT7420
+sensor. It should work with any platform featuring a I2C peripheral interface.
+It does not work on QEMU.
+In this example below the :ref:`nrf52_pca10040` board is used.
+
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/sensors/adt7420
+   :board: nrf52_pca10040
+   :goals: build flash
+
+Sample Output
+=============
+
+.. code-block:: console
+
+   device is 0x20002b74, name is ADT7420
+   temperature 24.984375 C
+   temperature 24.968750 C
+   temperature 24.968750 C
+   temperature 24.968750 C
+   temperature 24.953125 C
+
+<repeats endlessly>
+

samples/sensor/adt7420/dts.fixup

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+#if defined(CONFIG_HAS_DTS_I2C_DEVICE)
+
+#ifndef CONFIG_ADT7420_NAME
+#define CONFIG_ADT7420_NAME ""
+#define CONFIG_ADT7420_I2C_ADDR 0
+#define CONFIG_ADT7420_I2C_MASTER_DEV_NAME ""
+#endif
+
+#endif /* CONFIG_HAS_DTS_I2C_DEVICE */

samples/sensor/adt7420/prj.conf

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+CONFIG_STDOUT_CONSOLE=y
+CONFIG_I2C=y
+CONFIG_SENSOR=y
+CONFIG_ADT7420=y

samples/sensor/adt7420/sample.yaml

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+sample:
+  name: ADT7420 Sensor Sample
+tests:
+  test:
+    harness: sensor
+    tags: samples
+    depends_on: i2c

samples/sensor/adt7420/src/main.c

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+/*
+ * Copyright (c) 2018 Analog Devices Inc.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr.h>
+#include <device.h>
+#include <sensor.h>
+#include <stdio.h>
+#include <misc/__assert.h>
+
+K_SEM_DEFINE(sem, 0, 1);
+
+static void trigger_handler(struct device *dev, struct sensor_trigger *trigger)
+{
+	k_sem_give(&sem);
+}
+
+static int sensor_set_attribute(struct device *dev, enum sensor_channel chan,
+				enum sensor_attribute attr, int value)
+{
+	struct sensor_value sensor_val;
+	int ret;
+
+	sensor_val.val1 = value / 1000000;
+	sensor_val.val2 = value % 1000000;
+
+	ret = sensor_attr_set(dev, chan, attr, &sensor_val);
+	if (ret) {
+		printf("sensor_attr_set failed ret %d\n", ret);
+	}
+
+	return ret;
+}
+
+static void process(struct device *dev)
+{
+	struct sensor_value temp_val;
+	int ret;
+
+	/* Set upddate rate to 240 mHz */
+	sensor_set_attribute(dev, SENSOR_CHAN_AMBIENT_TEMP,
+			     SENSOR_ATTR_SAMPLING_FREQUENCY, 240 * 1000);
+
+	if (IS_ENABLED(CONFIG_ADT7420_TRIGGER)) {
+		struct sensor_trigger trig = {
+			.type = SENSOR_TRIG_THRESHOLD,
+			.chan = SENSOR_CHAN_AMBIENT_TEMP,
+		};
+
+		/* Set lower and upper threshold to 10 and 30 °C */
+		sensor_set_attribute(dev, SENSOR_CHAN_AMBIENT_TEMP,
+				     SENSOR_ATTR_UPPER_THRESH, 30 * 1000000);
+		sensor_set_attribute(dev, SENSOR_CHAN_AMBIENT_TEMP,
+				     SENSOR_ATTR_LOWER_THRESH, 10 * 1000000);
+
+		if (sensor_trigger_set(dev, &trig, trigger_handler)) {
+			printf("Could not set trigger\n");
+			return;
+		}
+	}
+
+	while (1) {
+		if (IS_ENABLED(CONFIG_ADT7420_TRIGGER)) {
+			printf("Waiting for a threshold event\n");
+			k_sem_take(&sem, K_FOREVER);
+		}
+
+		ret = sensor_sample_fetch(dev);
+		if (ret) {
+			printf("sensor_sample_fetch failed ret %d\n", ret);
+			return;
+		}
+
+		ret = sensor_channel_get(dev, SENSOR_CHAN_AMBIENT_TEMP,
+					 &temp_val);
+		if (ret) {
+			printf("sensor_channel_get failed ret %d\n", ret);
+			return;
+		}
+
+		printf("temperature %.6f C\n",
+		       sensor_value_to_double(&temp_val));
+
+		if (!IS_ENABLED(CONFIG_ADT7420_TRIGGER)) {
+			k_sleep(1000);
+		}
+	}
+}
+
+void main(void)
+{
+	struct device *dev = device_get_binding(CONFIG_ADT7420_NAME);
+
+	__ASSERT(dev != NULL, "Failed to get device binding");
+	printf("device is %p, name is %s\n", dev, dev->config->name);
+
+	process(dev);
+}