samples: sensor: dht: add sample

Add a sample to test the Aosong temperature/humidity sensor.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>

samples/sensor/dht/CMakeLists.txt

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+#
+# Copyright (c) 2019 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+cmake_minimum_required(VERSION 3.13.1)
+include($ENV{ZEPHYR_BASE}/cmake/app/boilerplate.cmake NO_POLICY_SCOPE)
+project(dht)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

samples/sensor/dht/README.rst

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+.. _dht:
+
+DHT: Aosong DHT Digital-output Humidity and Temperature Sensor
+##############################################################
+
+Description
+***********
+
+This sample application periodically (0.5 Hz) measures the ambient
+temperature and humidity. The result is written to the console.
+
+Wiring
+*******
+
+This sample uses an external breakout for the sensor.  A devicetree
+overlay must be provided to identify the sensor variant and the GPIO
+used to control the sensor.
+
+Building and Running
+********************
+
+After providing a devicetree overlay that specifies the sensor location,
+build this sample app using:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/sensor/dht
+   :board: nrf52_pca10040
+   :goals: build flash
+
+Sample Output
+=============
+
+.. code-block:: console
+
+   *** Booting Zephyr OS build zephyr-v2.1.0-329-g38418b26c4cc  ***
+   [0:00:00.027]: 20.0 Cel ; 48.7 %RH
+   [0:00:02.053]: 19.8 Cel ; 48.7 %RH
+   [0:00:04.079]: 20.0 Cel ; 48.7 %RH
+   [0:00:06.105]: 19.8 Cel ; 48.7 %RH
+   [0:00:08.130]: 20.0 Cel ; 48.8 %RH
+   [0:00:10.156]: 20.1 Cel ; 48.8 %RH
+   [0:00:12.182]: 19.7 Cel ; 48.7 %RH
+   [0:00:14.207]: 20.0 Cel ; 48.8 %RH
+
+<repeats endlessly>

samples/sensor/dht/boards/nrf52_pca10040.overlay

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+/*
+ * Copyright (c) 2019 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	dht22 {
+		compatible = "aosong,dht";
+		status = "okay";
+		label = "DHT22";
+		dio-gpios = <&gpio0 11 0>;
+		dht22;
+	};
+};

samples/sensor/dht/prj.conf

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+#
+# Copyright (c) 2019 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+CONFIG_SENSOR=y
+CONFIG_GPIO=y
+CONFIG_DHT=y
+
+# Need float format support
+CONFIG_NEWLIB_LIBC=y
+CONFIG_NEWLIB_LIBC_NANO=n
+CONFIG_NEWLIB_LIBC_FLOAT_PRINTF=y

samples/sensor/dht/sample.yaml

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+#
+# Copyright (c) 2019 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+sample:
+  name: DHT Sensor Sample
+tests:
+  sample.sensor.dht:
+    build_only: true
+    platform_whitelist: nrf52_pca10040
+    tags: sensors

samples/sensor/dht/src/main.c

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+/*
+ * Copyright (c) 2019 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr.h>
+#include <device.h>
+#include <drivers/sensor.h>
+#include <stdio.h>
+
+static const char *now_str(void)
+{
+	static char buf[16]; /* ...HH:MM:SS.MMM */
+	u32_t now = k_uptime_get_32();
+	unsigned int ms = now % MSEC_PER_SEC;
+	unsigned int s;
+	unsigned int min;
+	unsigned int h;
+
+	now /= MSEC_PER_SEC;
+	s = now % 60U;
+	now /= 60U;
+	min = now % 60U;
+	now /= 60U;
+	h = now;
+
+	snprintf(buf, sizeof(buf), "%u:%02u:%02u.%03u",
+		 h, min, s, ms);
+	return buf;
+}
+
+void main(void)
+{
+	const char *const label = DT_INST_0_AOSONG_DHT_LABEL;
+	struct device *dht22 = device_get_binding(label);
+
+	if (!dht22) {
+		printf("Failed to find sensor %s\n", label);
+		return;
+	}
+
+	while (true) {
+		int rc = sensor_sample_fetch(dht22);
+
+		if (rc != 0) {
+			printf("Sensor fetch failed: %d\n", rc);
+			break;
+		}
+
+		struct sensor_value temperature;
+		struct sensor_value humidity;
+
+		rc = sensor_channel_get(dht22, SENSOR_CHAN_AMBIENT_TEMP,
+					&temperature);
+		if (rc == 0) {
+			rc = sensor_channel_get(dht22, SENSOR_CHAN_HUMIDITY,
+						&humidity);
+		}
+		if (rc != 0) {
+			printf("get failed: %d\n", rc);
+			break;
+		}
+
+		printf("[%s]: %.1f Cel ; %.1f %%RH\n",
+		       now_str(),
+		       sensor_value_to_double(&temperature),
+		       sensor_value_to_double(&humidity));
+		k_sleep(K_SECONDS(2));
+	}
+}