samples: bluetooth: nus: Add Peripheral NUS sample

Demonstrating basic usage of NUS to exchange data.

Signed-off-by: Luis Ubieda <luisf@croxel.com>

samples/bluetooth/peripheral_nus/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.20.0)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(peripheral_nus)
+
+target_sources(app PRIVATE
+        src/main.c
+)

samples/bluetooth/peripheral_nus/README.rst

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+.. _peripheral_nus:
+
+Bluetooth: Peripheral NUS
+#########################
+
+Overview
+********
+
+This sample demonstrates the usage of the NUS service (Nordic UART Service) as a serial
+endpoint to exchange data. In this case, the sample assumes the data is UTF-8 encoded,
+but it may be binary data. Once the user connects to the device and subscribes to the TX
+characteristic, it will start receiving periodic notifications with "Hello World!\n".
+
+Requirements
+************
+
+* BlueZ running on the host, or
+* A board with BLE support
+
+Building and Running
+********************
+
+This sample can be found under :zephyr_file:`samples/bluetooth/peripheral_nus` in the
+Zephyr tree.
+
+See :ref:`bluetooth samples section <bluetooth-samples>` for details.

samples/bluetooth/peripheral_nus/prj.conf

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+CONFIG_BT=y
+CONFIG_BT_PERIPHERAL=y
+CONFIG_BT_NUS=y

samples/bluetooth/peripheral_nus/sample.yaml

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+sample:
+  name: Bluetooth Peripheral NUS
+  description: Demonstrates the NUS GATT Service (Nordic UART Service)
+tests:
+  sample.bluetooth.peripheral_nus:
+    harness: bluetooth
+    platform_allow:
+      - qemu_cortex_m3
+      - qemu_x86
+      - nrf52840dk/nrf52840
+    integration_platforms:
+      - qemu_cortex_m3
+    tags: bluetooth

samples/bluetooth/peripheral_nus/src/main.c

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+/*
+ * Copyright (c) 2024 Croxel, Inc.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+#include <zephyr/bluetooth/bluetooth.h>
+#include <zephyr/bluetooth/services/nus.h>
+
+#define DEVICE_NAME		CONFIG_BT_DEVICE_NAME
+#define DEVICE_NAME_LEN		(sizeof(DEVICE_NAME) - 1)
+
+static const struct bt_data ad[] = {
+	BT_DATA_BYTES(BT_DATA_FLAGS, (BT_LE_AD_GENERAL | BT_LE_AD_NO_BREDR)),
+	BT_DATA(BT_DATA_NAME_COMPLETE, DEVICE_NAME, DEVICE_NAME_LEN),
+};
+
+static const struct bt_data sd[] = {
+	BT_DATA_BYTES(BT_DATA_UUID128_ALL, BT_UUID_NUS_SRV_VAL),
+};
+
+static void notif_enabled(bool enabled, void *ctx)
+{
+	ARG_UNUSED(ctx);
+
+	printk("%s() - %s\n", __func__, (enabled ? "Enabled" : "Disabled"));
+}
+
+static void received(struct bt_conn *conn, const void *data, uint16_t len, void *ctx)
+{
+	char message[CONFIG_BT_L2CAP_TX_MTU + 1] = "";
+
+	ARG_UNUSED(conn);
+	ARG_UNUSED(ctx);
+
+	memcpy(message, data, MIN(sizeof(message) - 1, len));
+	printk("%s() - Len: %d, Message: %s\n", __func__, len, message);
+}
+
+struct bt_nus_cb nus_listener = {
+	.notif_enabled = notif_enabled,
+	.received = received,
+};
+
+int main(void)
+{
+	int err;
+
+	printk("Sample - Bluetooth Peripheral NUS\n");
+
+	err = bt_nus_cb_register(&nus_listener, NULL);
+	if (err) {
+		printk("Failed to register NUS callback: %d\n", err);
+		return err;
+	}
+
+	err = bt_enable(NULL);
+	if (err) {
+		printk("Failed to enable bluetooth: %d\n", err);
+		return err;
+	}
+
+	err = bt_le_adv_start(BT_LE_ADV_CONN, ad, ARRAY_SIZE(ad), sd, ARRAY_SIZE(sd));
+	if (err) {
+		printk("Failed to start advertising: %d\n", err);
+		return err;
+	}
+
+	printk("Initialization complete\n");
+
+	while (true) {
+		const char *hello_world = "Hello World!\n";
+
+		k_sleep(K_SECONDS(3));
+
+		err = bt_nus_send(NULL, hello_world, strlen(hello_world));
+		printk("Data send - Result: %d\n", err);
+
+		if (err < 0 && (err != -EAGAIN) && (err != -ENOTCONN)) {
+			return err;
+		}
+	}
+
+	return 0;
+}