init commit from esp-idf ble example

main/CMakeLists.txt

@@ -0,0 +1,5 @@
+file(GLOB_RECURSE srcs "main.c" "src/*.c")
+
+idf_component_register(SRCS "${srcs}"
+                       PRIV_REQUIRES bt nvs_flash esp_driver_gpio
+                       INCLUDE_DIRS "./include")

main/Kconfig.projbuild

@@ -0,0 +1,42 @@
+menu "Example Configuration"
+
+    orsource "$IDF_PATH/examples/common_components/env_caps/$IDF_TARGET/Kconfig.env_caps"
+
+    choice BLINK_LED
+        prompt "Blink LED type"
+        default BLINK_LED_GPIO
+        help
+            Select the LED type. A normal level controlled LED or an addressable LED strip.
+            The default selection is based on the Espressif DevKit boards.
+            You can change the default selection according to your board.
+
+        config BLINK_LED_GPIO
+            bool "GPIO"
+        config BLINK_LED_STRIP
+            bool "LED strip"
+    endchoice
+
+    choice BLINK_LED_STRIP_BACKEND
+        depends on BLINK_LED_STRIP
+        prompt "LED strip backend peripheral"
+        default BLINK_LED_STRIP_BACKEND_RMT if SOC_RMT_SUPPORTED
+        default BLINK_LED_STRIP_BACKEND_SPI
+        help
+            Select the backend peripheral to drive the LED strip.
+
+        config BLINK_LED_STRIP_BACKEND_RMT
+            depends on SOC_RMT_SUPPORTED
+            bool "RMT"
+        config BLINK_LED_STRIP_BACKEND_SPI
+            bool "SPI"
+    endchoice
+
+    config BLINK_GPIO
+        int "Blink GPIO number"
+        range ENV_GPIO_RANGE_MIN ENV_GPIO_OUT_RANGE_MAX
+        default 8
+        help
+            GPIO number (IOxx) to blink on and off the LED.
+            Some GPIOs are used for other purposes (flash connections, etc.) and cannot be used to blink.
+
+endmenu

main/idf_component.yml

@@ -0,0 +1,2 @@
+dependencies:
+  espressif/led_strip: "^2.4.1"

main/include/common.h

@@ -0,0 +1,32 @@
+#ifndef COMMON_H
+#define COMMON_H
+
+/* Includes */
+/* STD APIs */
+#include <assert.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+
+/* ESP APIs */
+#include "esp_log.h"
+#include "nvs_flash.h"
+#include "sdkconfig.h"
+
+/* FreeRTOS APIs */
+#include <freertos/FreeRTOS.h>
+#include <freertos/task.h>
+
+/* NimBLE stack APIs */
+#include "host/ble_hs.h"
+#include "host/ble_uuid.h"
+#include "host/util/util.h"
+#include "nimble/ble.h"
+#include "nimble/nimble_port.h"
+#include "nimble/nimble_port_freertos.h"
+
+/* Defines */
+#define TAG "NimBLE_GATT_Server"
+#define DEVICE_NAME "NimBLE_GATT"
+
+#endif // COMMON_H

main/include/gap.h

@@ -0,0 +1,18 @@
+#ifndef GAP_SVC_H
+#define GAP_SVC_H
+
+/* Includes */
+/* NimBLE GAP APIs */
+#include "host/ble_gap.h"
+#include "services/gap/ble_svc_gap.h"
+
+/* Defines */
+#define BLE_GAP_APPEARANCE_GENERIC_TAG 0x0200
+#define BLE_GAP_URI_PREFIX_HTTPS 0x17
+#define BLE_GAP_LE_ROLE_PERIPHERAL 0x00
+
+/* Public function declarations */
+void adv_init(void);
+int gap_init(void);
+
+#endif // GAP_SVC_H

main/include/gatt_svc.h

@@ -0,0 +1,18 @@
+#ifndef GATT_SVR_H
+#define GATT_SVR_H
+
+/* Includes */
+/* NimBLE GATT APIs */
+#include "host/ble_gatt.h"
+#include "services/gatt/ble_svc_gatt.h"
+
+/* NimBLE GAP APIs */
+#include "host/ble_gap.h"
+
+/* Public function declarations */
+void send_heart_rate_indication(void);
+void gatt_svr_register_cb(struct ble_gatt_register_ctxt *ctxt, void *arg);
+void gatt_svr_subscribe_cb(struct ble_gap_event *event);
+int gatt_svc_init(void);
+
+#endif // GATT_SVR_H

main/include/heart_rate.h

@@ -0,0 +1,15 @@
+#ifndef HEART_RATE_H
+#define HEART_RATE_H
+
+/* Includes */
+/* ESP APIs */
+#include "esp_random.h"
+
+/* Defines */
+#define HEART_RATE_TASK_PERIOD (1000 / portTICK_PERIOD_MS)
+
+/* Public function declarations */
+uint8_t get_heart_rate(void);
+void update_heart_rate(void);
+
+#endif // HEART_RATE_H

main/include/led.h

@@ -0,0 +1,19 @@
+#ifndef LED_H
+#define LED_H
+
+/* Includes */
+/* ESP APIs */
+#include "driver/gpio.h"
+#include "led_strip.h"
+#include "sdkconfig.h"
+
+/* Defines */
+#define BLINK_GPIO CONFIG_BLINK_GPIO
+
+/* Public function declarations */
+uint8_t get_led_state(void);
+void led_on(void);
+void led_off(void);
+void led_init(void);
+
+#endif // LED_H

main/main.c

@@ -0,0 +1,128 @@
+/* Includes */
+#include "common.h"
+#include "gap.h"
+#include "gatt_svc.h"
+#include "heart_rate.h"
+#include "led.h"
+
+/* Library function declarations */
+void ble_store_config_init(void);
+
+/* Private function declarations */
+static void on_stack_reset(int reason);
+static void on_stack_sync(void);
+static void nimble_host_config_init(void);
+static void nimble_host_task(void *param);
+
+/* Private functions */
+/*
+ *  Stack event callback functions
+ *      - on_stack_reset is called when host resets BLE stack due to errors
+ *      - on_stack_sync is called when host has synced with controller
+ */
+static void on_stack_reset(int reason) {
+    /* On reset, print reset reason to console */
+    ESP_LOGI(TAG, "nimble stack reset, reset reason: %d", reason);
+}
+
+static void on_stack_sync(void) {
+    /* On stack sync, do advertising initialization */
+    adv_init();
+}
+
+static void nimble_host_config_init(void) {
+    /* Set host callbacks */
+    ble_hs_cfg.reset_cb = on_stack_reset;
+    ble_hs_cfg.sync_cb = on_stack_sync;
+    ble_hs_cfg.gatts_register_cb = gatt_svr_register_cb;
+    ble_hs_cfg.store_status_cb = ble_store_util_status_rr;
+
+    /* Store host configuration */
+    ble_store_config_init();
+}
+
+static void nimble_host_task(void *param) {
+    /* Task entry log */
+    ESP_LOGI(TAG, "nimble host task has been started!");
+
+    /* This function won't return until nimble_port_stop() is executed */
+    nimble_port_run();
+
+    /* Clean up at exit */
+    vTaskDelete(NULL);
+}
+
+static void heart_rate_task(void *param) {
+    /* Task entry log */
+    ESP_LOGI(TAG, "heart rate task has been started!");
+
+    /* Loop forever */
+    while (1) {
+        /* Update heart rate value every 1 second */
+        update_heart_rate();
+        ESP_LOGI(TAG, "heart rate updated to %d", get_heart_rate());
+
+        /* Send heart rate indication if enabled */
+        send_heart_rate_indication();
+
+        /* Sleep */
+        vTaskDelay(HEART_RATE_TASK_PERIOD);
+    }
+
+    /* Clean up at exit */
+    vTaskDelete(NULL);
+}
+
+void app_main(void) {
+    /* Local variables */
+    int rc;
+    esp_err_t ret;
+
+    /* LED initialization */
+    led_init();
+
+    /*
+     * NVS flash initialization
+     * Dependency of BLE stack to store configurations
+     */
+    ret = nvs_flash_init();
+    if (ret == ESP_ERR_NVS_NO_FREE_PAGES ||
+        ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {
+        ESP_ERROR_CHECK(nvs_flash_erase());
+        ret = nvs_flash_init();
+    }
+    if (ret != ESP_OK) {
+        ESP_LOGE(TAG, "failed to initialize nvs flash, error code: %d ", ret);
+        return;
+    }
+
+    /* NimBLE stack initialization */
+    ret = nimble_port_init();
+    if (ret != ESP_OK) {
+        ESP_LOGE(TAG, "failed to initialize nimble stack, error code: %d ",
+                 ret);
+        return;
+    }
+
+    /* GAP service initialization */
+    rc = gap_init();
+    if (rc != 0) {
+        ESP_LOGE(TAG, "failed to initialize GAP service, error code: %d", rc);
+        return;
+    }
+
+    /* GATT server initialization */
+    rc = gatt_svc_init();
+    if (rc != 0) {
+        ESP_LOGE(TAG, "failed to initialize GATT server, error code: %d", rc);
+        return;
+    }
+
+    /* NimBLE host configuration initialization */
+    nimble_host_config_init();
+
+    /* Start NimBLE host task thread and return */
+    xTaskCreate(nimble_host_task, "NimBLE Host", 4*1024, NULL, 5, NULL);
+    xTaskCreate(heart_rate_task, "Heart Rate", 4*1024, NULL, 5, NULL);
+    return;
+}

main/src/gap.c

@@ -0,0 +1,300 @@
+#include "gap.h"
+#include "common.h"
+#include "gatt_svc.h"
+
+/* Private function declarations */
+inline static void format_addr(char *addr_str, uint8_t addr[]);
+static void print_conn_desc(struct ble_gap_conn_desc *desc);
+static void start_advertising(void);
+static int gap_event_handler(struct ble_gap_event *event, void *arg);
+
+/* Private variables */
+static uint8_t own_addr_type;
+static uint8_t addr_val[6] = {0};
+static uint8_t esp_uri[] = {BLE_GAP_URI_PREFIX_HTTPS, '/', '/', 'e', 's', 'p', 'r', 'e', 's', 's', 'i', 'f', '.', 'c', 'o', 'm'};
+
+/* Private functions */
+inline static void format_addr(char *addr_str, uint8_t addr[]) {
+    sprintf(addr_str, "%02X:%02X:%02X:%02X:%02X:%02X", addr[0], addr[1],
+            addr[2], addr[3], addr[4], addr[5]);
+}
+
+static void print_conn_desc(struct ble_gap_conn_desc *desc) {
+    /* Local variables */
+    char addr_str[18] = {0};
+
+    /* Connection handle */
+    ESP_LOGI(TAG, "connection handle: %d", desc->conn_handle);
+
+    /* Local ID address */
+    format_addr(addr_str, desc->our_id_addr.val);
+    ESP_LOGI(TAG, "device id address: type=%d, value=%s",
+             desc->our_id_addr.type, addr_str);
+
+    /* Peer ID address */
+    format_addr(addr_str, desc->peer_id_addr.val);
+    ESP_LOGI(TAG, "peer id address: type=%d, value=%s", desc->peer_id_addr.type,
+             addr_str);
+
+    /* Connection info */
+    ESP_LOGI(TAG,
+             "conn_itvl=%d, conn_latency=%d, supervision_timeout=%d, "
+             "encrypted=%d, authenticated=%d, bonded=%d\n",
+             desc->conn_itvl, desc->conn_latency, desc->supervision_timeout,
+             desc->sec_state.encrypted, desc->sec_state.authenticated,
+             desc->sec_state.bonded);
+}
+
+static void start_advertising(void) {
+    /* Local variables */
+    int rc = 0;
+    const char *name;
+    struct ble_hs_adv_fields adv_fields = {0};
+    struct ble_hs_adv_fields rsp_fields = {0};
+    struct ble_gap_adv_params adv_params = {0};
+
+    /* Set advertising flags */
+    adv_fields.flags = BLE_HS_ADV_F_DISC_GEN | BLE_HS_ADV_F_BREDR_UNSUP;
+
+    /* Set device name */
+    name = ble_svc_gap_device_name();
+    adv_fields.name = (uint8_t *)name;
+    adv_fields.name_len = strlen(name);
+    adv_fields.name_is_complete = 1;
+
+    /* Set device tx power */
+    adv_fields.tx_pwr_lvl = BLE_HS_ADV_TX_PWR_LVL_AUTO;
+    adv_fields.tx_pwr_lvl_is_present = 1;
+
+    /* Set device appearance */
+    adv_fields.appearance = BLE_GAP_APPEARANCE_GENERIC_TAG;
+    adv_fields.appearance_is_present = 1;
+
+    /* Set device LE role */
+    adv_fields.le_role = BLE_GAP_LE_ROLE_PERIPHERAL;
+    adv_fields.le_role_is_present = 1;
+
+    /* Set advertiement fields */
+    rc = ble_gap_adv_set_fields(&adv_fields);
+    if (rc != 0) {
+        ESP_LOGE(TAG, "failed to set advertising data, error code: %d", rc);
+        return;
+    }
+
+    /* Set device address */
+    rsp_fields.device_addr = addr_val;
+    rsp_fields.device_addr_type = own_addr_type;
+    rsp_fields.device_addr_is_present = 1;
+
+    /* Set URI */
+    rsp_fields.uri = esp_uri;
+    rsp_fields.uri_len = sizeof(esp_uri);
+
+    /* Set advertising interval */
+    rsp_fields.adv_itvl = BLE_GAP_ADV_ITVL_MS(500);
+    rsp_fields.adv_itvl_is_present = 1;
+
+    /* Set scan response fields */
+    rc = ble_gap_adv_rsp_set_fields(&rsp_fields);
+    if (rc != 0) {
+        ESP_LOGE(TAG, "failed to set scan response data, error code: %d", rc);
+        return;
+    }
+
+    /* Set non-connetable and general discoverable mode to be a beacon */
+    adv_params.conn_mode = BLE_GAP_CONN_MODE_UND;
+    adv_params.disc_mode = BLE_GAP_DISC_MODE_GEN;
+
+    /* Set advertising interval */
+    adv_params.itvl_min = BLE_GAP_ADV_ITVL_MS(500);
+    adv_params.itvl_max = BLE_GAP_ADV_ITVL_MS(510);
+
+    /* Start advertising */
+    rc = ble_gap_adv_start(own_addr_type, NULL, BLE_HS_FOREVER, &adv_params,
+                           gap_event_handler, NULL);
+    if (rc != 0) {
+        ESP_LOGE(TAG, "failed to start advertising, error code: %d", rc);
+        return;
+    }
+    ESP_LOGI(TAG, "advertising started!");
+}
+
+/*
+ * NimBLE applies an event-driven model to keep GAP service going
+ * gap_event_handler is a callback function registered when calling
+ * ble_gap_adv_start API and called when a GAP event arrives
+ */
+static int gap_event_handler(struct ble_gap_event *event, void *arg) {
+    /* Local variables */
+    int rc = 0;
+    struct ble_gap_conn_desc desc;
+
+    /* Handle different GAP event */
+    switch (event->type) {
+
+    /* Connect event */
+    case BLE_GAP_EVENT_CONNECT:
+        /* A new connection was established or a connection attempt failed. */
+        ESP_LOGI(TAG, "connection %s; status=%d",
+                 event->connect.status == 0 ? "established" : "failed",
+                 event->connect.status);
+
+        /* Connection succeeded */
+        if (event->connect.status == 0) {
+            /* Check connection handle */
+            rc = ble_gap_conn_find(event->connect.conn_handle, &desc);
+            if (rc != 0) {
+                ESP_LOGE(TAG,
+                         "failed to find connection by handle, error code: %d",
+                         rc);
+                return rc;
+            }
+
+            /* Print connection descriptor */
+            print_conn_desc(&desc);
+
+            /* Try to update connection parameters */
+            struct ble_gap_upd_params params = {.itvl_min = desc.conn_itvl,
+                                                .itvl_max = desc.conn_itvl,
+                                                .latency = 3,
+                                                .supervision_timeout =
+                                                    desc.supervision_timeout};
+            rc = ble_gap_update_params(event->connect.conn_handle, &params);
+            if (rc != 0) {
+                ESP_LOGE(
+                    TAG,
+                    "failed to update connection parameters, error code: %d",
+                    rc);
+                return rc;
+            }
+        }
+        /* Connection failed, restart advertising */
+        else {
+            start_advertising();
+        }
+        return rc;
+
+    /* Disconnect event */
+    case BLE_GAP_EVENT_DISCONNECT:
+        /* A connection was terminated, print connection descriptor */
+        ESP_LOGI(TAG, "disconnected from peer; reason=%d",
+                 event->disconnect.reason);
+
+        /* Restart advertising */
+        start_advertising();
+        return rc;
+
+    /* Connection parameters update event */
+    case BLE_GAP_EVENT_CONN_UPDATE:
+        /* The central has updated the connection parameters. */
+        ESP_LOGI(TAG, "connection updated; status=%d",
+                 event->conn_update.status);
+
+        /* Print connection descriptor */
+        rc = ble_gap_conn_find(event->conn_update.conn_handle, &desc);
+        if (rc != 0) {
+            ESP_LOGE(TAG, "failed to find connection by handle, error code: %d",
+                     rc);
+            return rc;
+        }
+        print_conn_desc(&desc);
+        return rc;
+
+    /* Advertising complete event */
+    case BLE_GAP_EVENT_ADV_COMPLETE:
+        /* Advertising completed, restart advertising */
+        ESP_LOGI(TAG, "advertise complete; reason=%d",
+                 event->adv_complete.reason);
+        start_advertising();
+        return rc;
+
+    /* Notification sent event */
+    case BLE_GAP_EVENT_NOTIFY_TX:
+        if ((event->notify_tx.status != 0) &&
+            (event->notify_tx.status != BLE_HS_EDONE)) {
+            /* Print notification info on error */
+            ESP_LOGI(TAG,
+                     "notify event; conn_handle=%d attr_handle=%d "
+                     "status=%d is_indication=%d",
+                     event->notify_tx.conn_handle, event->notify_tx.attr_handle,
+                     event->notify_tx.status, event->notify_tx.indication);
+        }
+        return rc;
+
+    /* Subscribe event */
+    case BLE_GAP_EVENT_SUBSCRIBE:
+        /* Print subscription info to log */
+        ESP_LOGI(TAG,
+                 "subscribe event; conn_handle=%d attr_handle=%d "
+                 "reason=%d prevn=%d curn=%d previ=%d curi=%d",
+                 event->subscribe.conn_handle, event->subscribe.attr_handle,
+                 event->subscribe.reason, event->subscribe.prev_notify,
+                 event->subscribe.cur_notify, event->subscribe.prev_indicate,
+                 event->subscribe.cur_indicate);
+
+        /* GATT subscribe event callback */
+        gatt_svr_subscribe_cb(event);
+        return rc;
+
+    /* MTU update event */
+    case BLE_GAP_EVENT_MTU:
+        /* Print MTU update info to log */
+        ESP_LOGI(TAG, "mtu update event; conn_handle=%d cid=%d mtu=%d",
+                 event->mtu.conn_handle, event->mtu.channel_id,
+                 event->mtu.value);
+        return rc;
+    }
+
+    return rc;
+}
+
+
+/* Public functions */
+void adv_init(void) {
+    /* Local variables */
+    int rc = 0;
+    char addr_str[18] = {0};
+
+    /* Make sure we have proper BT identity address set (random preferred) */
+    rc = ble_hs_util_ensure_addr(0);
+    if (rc != 0) {
+        ESP_LOGE(TAG, "device does not have any available bt address!");
+        return;
+    }
+
+    /* Figure out BT address to use while advertising (no privacy for now) */
+    rc = ble_hs_id_infer_auto(0, &own_addr_type);
+    if (rc != 0) {
+        ESP_LOGE(TAG, "failed to infer address type, error code: %d", rc);
+        return;
+    }
+
+    /* Printing ADDR */
+    rc = ble_hs_id_copy_addr(own_addr_type, addr_val, NULL);
+    if (rc != 0) {
+        ESP_LOGE(TAG, "failed to copy device address, error code: %d", rc);
+        return;
+    }
+    format_addr(addr_str, addr_val);
+    ESP_LOGI(TAG, "device address: %s", addr_str);
+
+    /* Start advertising. */
+    start_advertising();
+}
+
+int gap_init(void) {
+    /* Local variables */
+    int rc = 0;
+
+    /* Call NimBLE GAP initialization API */
+    ble_svc_gap_init();
+
+    /* Set GAP device name */
+    rc = ble_svc_gap_device_name_set(DEVICE_NAME);
+    if (rc != 0) {
+        ESP_LOGE(TAG, "failed to set device name to %s, error code: %d",
+                 DEVICE_NAME, rc);
+        return rc;
+    }
+    return rc;
+}

main/src/gatt_svc.c

@@ -0,0 +1,264 @@
+/* Includes */
+#include "gatt_svc.h"
+#include "common.h"
+#include "heart_rate.h"
+#include "led.h"
+
+/* Private function declarations */
+static int heart_rate_chr_access(uint16_t conn_handle, uint16_t attr_handle,
+                                 struct ble_gatt_access_ctxt *ctxt, void *arg);
+static int led_chr_access(uint16_t conn_handle, uint16_t attr_handle,
+                          struct ble_gatt_access_ctxt *ctxt, void *arg);
+
+/* Private variables */
+/* Heart rate service */
+static const ble_uuid16_t heart_rate_svc_uuid = BLE_UUID16_INIT(0x180D);
+
+static uint8_t heart_rate_chr_val[2] = {0};
+static uint16_t heart_rate_chr_val_handle;
+static const ble_uuid16_t heart_rate_chr_uuid = BLE_UUID16_INIT(0x2A37);
+
+static uint16_t heart_rate_chr_conn_handle = 0;
+static bool heart_rate_chr_conn_handle_inited = false;
+static bool heart_rate_ind_status = false;
+
+/* Automation IO service */
+static const ble_uuid16_t auto_io_svc_uuid = BLE_UUID16_INIT(0x1815);
+static uint16_t led_chr_val_handle;
+static const ble_uuid128_t led_chr_uuid =
+    BLE_UUID128_INIT(0x23, 0xd1, 0xbc, 0xea, 0x5f, 0x78, 0x23, 0x15, 0xde, 0xef,
+                     0x12, 0x12, 0x25, 0x15, 0x00, 0x00);
+
+/* GATT services table */
+static const struct ble_gatt_svc_def gatt_svr_svcs[] = {
+    /* Heart rate service */
+    {.type = BLE_GATT_SVC_TYPE_PRIMARY,
+     .uuid = &heart_rate_svc_uuid.u,
+     .characteristics =
+         (struct ble_gatt_chr_def[]){
+             {/* Heart rate characteristic */
+              .uuid = &heart_rate_chr_uuid.u,
+              .access_cb = heart_rate_chr_access,
+              .flags = BLE_GATT_CHR_F_READ | BLE_GATT_CHR_F_INDICATE,
+              .val_handle = &heart_rate_chr_val_handle},
+             {
+                 0, /* No more characteristics in this service. */
+             }}},
+
+    /* Automation IO service */
+    {
+        .type = BLE_GATT_SVC_TYPE_PRIMARY,
+        .uuid = &auto_io_svc_uuid.u,
+        .characteristics =
+            (struct ble_gatt_chr_def[]){/* LED characteristic */
+                                        {.uuid = &led_chr_uuid.u,
+                                         .access_cb = led_chr_access,
+                                         .flags = BLE_GATT_CHR_F_WRITE,
+                                         .val_handle = &led_chr_val_handle},
+                                        {0}},
+    },
+
+    {
+        0, /* No more services. */
+    },
+};
+
+/* Private functions */
+static int heart_rate_chr_access(uint16_t conn_handle, uint16_t attr_handle,
+                                 struct ble_gatt_access_ctxt *ctxt, void *arg) {
+    /* Local variables */
+    int rc;
+
+    /* Handle access events */
+    /* Note: Heart rate characteristic is read only */
+    switch (ctxt->op) {
+
+    /* Read characteristic event */
+    case BLE_GATT_ACCESS_OP_READ_CHR:
+        /* Verify connection handle */
+        if (conn_handle != BLE_HS_CONN_HANDLE_NONE) {
+            ESP_LOGI(TAG, "characteristic read; conn_handle=%d attr_handle=%d",
+                     conn_handle, attr_handle);
+        } else {
+            ESP_LOGI(TAG, "characteristic read by nimble stack; attr_handle=%d",
+                     attr_handle);
+        }
+
+        /* Verify attribute handle */
+        if (attr_handle == heart_rate_chr_val_handle) {
+            /* Update access buffer value */
+            heart_rate_chr_val[1] = get_heart_rate();
+            rc = os_mbuf_append(ctxt->om, &heart_rate_chr_val,
+                                sizeof(heart_rate_chr_val));
+            return rc == 0 ? 0 : BLE_ATT_ERR_INSUFFICIENT_RES;
+        }
+        goto error;
+
+    /* Unknown event */
+    default:
+        goto error;
+    }
+
+error:
+    ESP_LOGE(
+        TAG,
+        "unexpected access operation to heart rate characteristic, opcode: %d",
+        ctxt->op);
+    return BLE_ATT_ERR_UNLIKELY;
+}
+
+static int led_chr_access(uint16_t conn_handle, uint16_t attr_handle,
+                          struct ble_gatt_access_ctxt *ctxt, void *arg) {
+    /* Local variables */
+    int rc;
+
+    /* Handle access events */
+    /* Note: LED characteristic is write only */
+    switch (ctxt->op) {
+
+    /* Write characteristic event */
+    case BLE_GATT_ACCESS_OP_WRITE_CHR:
+        /* Verify connection handle */
+        if (conn_handle != BLE_HS_CONN_HANDLE_NONE) {
+            ESP_LOGI(TAG, "characteristic write; conn_handle=%d attr_handle=%d",
+                     conn_handle, attr_handle);
+        } else {
+            ESP_LOGI(TAG,
+                     "characteristic write by nimble stack; attr_handle=%d",
+                     attr_handle);
+        }
+
+        /* Verify attribute handle */
+        if (attr_handle == led_chr_val_handle) {
+            /* Verify access buffer length */
+            if (ctxt->om->om_len == 1) {
+                /* Turn the LED on or off according to the operation bit */
+                if (ctxt->om->om_data[0]) {
+                    led_on();
+                    ESP_LOGI(TAG, "led turned on!");
+                } else {
+                    led_off();
+                    ESP_LOGI(TAG, "led turned off!");
+                }
+            } else {
+                goto error;
+            }
+            return rc;
+        }
+        goto error;
+
+    /* Unknown event */
+    default:
+        goto error;
+    }
+
+error:
+    ESP_LOGE(TAG,
+             "unexpected access operation to led characteristic, opcode: %d",
+             ctxt->op);
+    return BLE_ATT_ERR_UNLIKELY;
+}
+
+/* Public functions */
+void send_heart_rate_indication(void) {
+    if (heart_rate_ind_status && heart_rate_chr_conn_handle_inited) {
+        ble_gatts_indicate(heart_rate_chr_conn_handle,
+                           heart_rate_chr_val_handle);
+        ESP_LOGI(TAG, "heart rate indication sent!");
+    }
+}
+
+/*
+ *  Handle GATT attribute register events
+ *      - Service register event
+ *      - Characteristic register event
+ *      - Descriptor register event
+ */
+void gatt_svr_register_cb(struct ble_gatt_register_ctxt *ctxt, void *arg) {
+    /* Local variables */
+    char buf[BLE_UUID_STR_LEN];
+
+    /* Handle GATT attributes register events */
+    switch (ctxt->op) {
+
+    /* Service register event */
+    case BLE_GATT_REGISTER_OP_SVC:
+        ESP_LOGD(TAG, "registered service %s with handle=%d",
+                 ble_uuid_to_str(ctxt->svc.svc_def->uuid, buf),
+                 ctxt->svc.handle);
+        break;
+
+    /* Characteristic register event */
+    case BLE_GATT_REGISTER_OP_CHR:
+        ESP_LOGD(TAG,
+                 "registering characteristic %s with "
+                 "def_handle=%d val_handle=%d",
+                 ble_uuid_to_str(ctxt->chr.chr_def->uuid, buf),
+                 ctxt->chr.def_handle, ctxt->chr.val_handle);
+        break;
+
+    /* Descriptor register event */
+    case BLE_GATT_REGISTER_OP_DSC:
+        ESP_LOGD(TAG, "registering descriptor %s with handle=%d",
+                 ble_uuid_to_str(ctxt->dsc.dsc_def->uuid, buf),
+                 ctxt->dsc.handle);
+        break;
+
+    /* Unknown event */
+    default:
+        assert(0);
+        break;
+    }
+}
+
+/*
+ *  GATT server subscribe event callback
+ *      1. Update heart rate subscription status
+ */
+
+void gatt_svr_subscribe_cb(struct ble_gap_event *event) {
+    /* Check connection handle */
+    if (event->subscribe.conn_handle != BLE_HS_CONN_HANDLE_NONE) {
+        ESP_LOGI(TAG, "subscribe event; conn_handle=%d attr_handle=%d",
+                 event->subscribe.conn_handle, event->subscribe.attr_handle);
+    } else {
+        ESP_LOGI(TAG, "subscribe by nimble stack; attr_handle=%d",
+                 event->subscribe.attr_handle);
+    }
+
+    /* Check attribute handle */
+    if (event->subscribe.attr_handle == heart_rate_chr_val_handle) {
+        /* Update heart rate subscription status */
+        heart_rate_chr_conn_handle = event->subscribe.conn_handle;
+        heart_rate_chr_conn_handle_inited = true;
+        heart_rate_ind_status = event->subscribe.cur_indicate;
+    }
+}
+
+/*
+ *  GATT server initialization
+ *      1. Initialize GATT service
+ *      2. Update NimBLE host GATT services counter
+ *      3. Add GATT services to server
+ */
+int gatt_svc_init(void) {
+    /* Local variables */
+    int rc;
+
+    /* 1. GATT service initialization */
+    ble_svc_gatt_init();
+
+    /* 2. Update GATT services counter */
+    rc = ble_gatts_count_cfg(gatt_svr_svcs);
+    if (rc != 0) {
+        return rc;
+    }
+
+    /* 3. Add GATT services */
+    rc = ble_gatts_add_svcs(gatt_svr_svcs);
+    if (rc != 0) {
+        return rc;
+    }
+
+    return 0;
+}

main/src/heart_rate_mock.c

@@ -0,0 +1,11 @@
+/* Includes */
+#include "common.h"
+#include "heart_rate.h"
+
+/* Private variables */
+static uint8_t heart_rate;
+
+/* Public functions */
+uint8_t get_heart_rate(void) { return heart_rate; }
+
+void update_heart_rate(void) { heart_rate = 60 + (uint8_t)(esp_random() % 21); }

main/src/led.c

@@ -0,0 +1,79 @@
+/* Includes */
+#include "led.h"
+#include "common.h"
+
+/* Private variables */
+static uint8_t led_state;
+
+#ifdef CONFIG_BLINK_LED_STRIP
+static led_strip_handle_t led_strip;
+#endif
+
+/* Public functions */
+uint8_t get_led_state(void) { return led_state; }
+
+#ifdef CONFIG_BLINK_LED_STRIP
+
+void led_on(void) {
+    /* Set the LED pixel using RGB from 0 (0%) to 255 (100%) for each color */
+    led_strip_set_pixel(led_strip, 0, 16, 16, 16);
+
+    /* Refresh the strip to send data */
+    led_strip_refresh(led_strip);
+
+    /* Update LED state */
+    led_state = true;
+}
+
+void led_off(void) {
+    /* Set all LED off to clear all pixels */
+    led_strip_clear(led_strip);
+
+    /* Update LED state */
+    led_state = false;
+}
+
+void led_init(void) {
+    ESP_LOGI(TAG, "example configured to blink addressable led!");
+    /* LED strip initialization with the GPIO and pixels number*/
+    led_strip_config_t strip_config = {
+        .strip_gpio_num = CONFIG_BLINK_GPIO,
+        .max_leds = 1, // at least one LED on board
+    };
+#if CONFIG_BLINK_LED_STRIP_BACKEND_RMT
+    led_strip_rmt_config_t rmt_config = {
+        .resolution_hz = 10 * 1000 * 1000, // 10MHz
+        .flags.with_dma = false,
+    };
+    ESP_ERROR_CHECK(
+        led_strip_new_rmt_device(&strip_config, &rmt_config, &led_strip));
+#elif CONFIG_BLINK_LED_STRIP_BACKEND_SPI
+    led_strip_spi_config_t spi_config = {
+        .spi_bus = SPI2_HOST,
+        .flags.with_dma = true,
+    };
+    ESP_ERROR_CHECK(
+        led_strip_new_spi_device(&strip_config, &spi_config, &led_strip));
+#else
+#error "unsupported LED strip backend"
+#endif
+    /* Set all LED off to clear all pixels */
+    led_off();
+}
+
+#elif CONFIG_BLINK_LED_GPIO
+
+void led_on(void) { gpio_set_level(CONFIG_BLINK_GPIO, true); }
+
+void led_off(void) { gpio_set_level(CONFIG_BLINK_GPIO, false); }
+
+void led_init(void) {
+    ESP_LOGI(TAG, "example configured to blink gpio led!");
+    gpio_reset_pin(CONFIG_BLINK_GPIO);
+    /* Set the GPIO as a push/pull output */
+    gpio_set_direction(CONFIG_BLINK_GPIO, GPIO_MODE_OUTPUT);
+}
+
+#else
+#error "unsupported LED type"
+#endif