examples: add NimBLE GATT server example app

examples/nimble_gatt/Makefile

+# name of your application
+APPLICATION = nimble_gatt
+
+# If no BOARD is found in the environment, use this default:
+BOARD ?= nrf52dk
+
+# So far, NimBLE only works on nRF52 based platforms
+BOARD_WHITELIST := nrf52dk nrf52840dk
+
+# This has to be the absolute path to the RIOT base directory:
+RIOTBASE ?= $(CURDIR)/../..
+
+# Include NimBLE
+USEPKG += nimble
+
+# Comment this out to disable code in RIOT that does safety checking
+# which is not needed in a production environment but helps in the
+# development process:
+DEVELHELP ?= 1
+
+# Change this to 0 show compiler invocation lines by default:
+QUIET ?= 1
+
+include $(RIOTBASE)/Makefile.include

examples/nimble_gatt/README.md

+NimBLE GATT Server Example
+==========================
+This example application configures and runs the NimBLE BLE stack as simple GATT
+server. It will provide two services, the build-in GAP and the build-in GATT
+service. The device will advertise itself by the name `NimBLE on RIOT`.
+
+To interact with the BLE device running this example, use any BLE client that is
+able to discover and interact with GATT services.
+An easy way to get started is to use a smartphone (supporting at least BT 4.0) with Nordic's `nRF Connect` App.

examples/nimble_gatt/main.c

+/*
+ * Copyright (C) 2018 Freie Universität Berlin
+ *               2018 Codecoup
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     examples
+ * @{
+ *
+ * @file
+ * @brief       BLE peripheral example using NimBLE
+ *
+ * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
+ * @author      Andrzej Kaczmarek <andrzej.kaczmarek@codecoup.pl>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+#include "nimble_riot.h"
+
+#include "nimble/nimble_port.h"
+#include "host/ble_hs.h"
+#include "host/util/util.h"
+#include "services/gap/ble_svc_gap.h"
+#include "services/gatt/ble_svc_gatt.h"
+
+static const char device_name[] = "NimBLE on RIOT";
+static uint8_t own_addr_type;
+
+
+static void start_advertise(void);
+
+static void put_ad(uint8_t ad_type, uint8_t ad_len, const void *ad, uint8_t *buf,
+                   uint8_t *len)
+{
+    buf[(*len)++] = ad_len + 1;
+    buf[(*len)++] = ad_type;
+
+    memcpy(&buf[*len], ad, ad_len);
+
+    *len += ad_len;
+}
+
+static void update_ad(void)
+{
+    uint8_t ad[BLE_HS_ADV_MAX_SZ];
+    uint8_t ad_len = 0;
+    uint8_t ad_flags = BLE_HS_ADV_F_DISC_GEN | BLE_HS_ADV_F_BREDR_UNSUP;
+
+    put_ad(BLE_HS_ADV_TYPE_FLAGS, 1, &ad_flags, ad, &ad_len);
+    put_ad(BLE_HS_ADV_TYPE_COMP_NAME, sizeof(device_name), device_name, ad, &ad_len);
+
+    ble_gap_adv_set_data(ad, ad_len);
+}
+
+static int gap_event_cb(struct ble_gap_event *event, void *arg)
+{
+    (void)arg;
+
+    switch (event->type) {
+        case BLE_GAP_EVENT_CONNECT:
+            if (event->connect.status) {
+                start_advertise();
+            }
+            break;
+
+        case BLE_GAP_EVENT_DISCONNECT:
+            start_advertise();
+            break;
+    }
+
+    return 0;
+}
+
+static void start_advertise(void)
+{
+    struct ble_gap_adv_params advp;
+    int rc;
+
+    memset(&advp, 0, sizeof advp);
+    advp.conn_mode = BLE_GAP_CONN_MODE_UND;
+    advp.disc_mode = BLE_GAP_DISC_MODE_GEN;
+    rc = ble_gap_adv_start(own_addr_type, NULL, BLE_HS_FOREVER,
+                           &advp, gap_event_cb, NULL);
+    assert(rc == 0);
+}
+
+static void app_ble_sync_cb(void)
+{
+    int rc;
+
+    rc = ble_hs_util_ensure_addr(0);
+    assert(rc == 0);
+
+    rc = ble_hs_id_infer_auto(0, &own_addr_type);
+    assert(rc == 0);
+
+    /* generate the advertising data */
+    update_ad();
+
+    start_advertise();
+}
+
+int main(void)
+{
+    puts("NimBLE GATT Server Example");
+
+    /* initialize NimBLE's controller */
+    nimble_riot_controller_init();
+
+    /* register the synchronization callback that is triggered once the host has
+     * finished its initialization */
+    ble_hs_cfg.sync_cb = app_ble_sync_cb;
+
+    /* initialize NimBLE porting layer and the default GATT and GAP services*/
+    nimble_port_init();
+    ble_svc_gap_init();
+    ble_svc_gatt_init();
+
+    /* set the device name */
+    ble_svc_gap_device_name_set(device_name);
+
+    /* and finally run NimBLE's host event loop. The event loop contains a pre-
+     * configured event which will trigger the hosts initialization */
+    nimble_port_run();
+
+    return 0;
+}