BLE service with multiple characteristics(client/switch and bulb/server)

[davidm]

I am new to C programming and BLE in general.I am trying to create a service with two characteristics,(the application simply is a modification of BLE bulb and switch). How the original application work is, on the client/switch if you push button 1, it turns on the LED 3 on the server/bulb, and when you push button 2 it turns it off.So it is only one service and one characteristic. The client acts as central and server acts as a peripheral.

What I want is to add another characteristic so that If I push button 3 on the client to turn on  LED 4 on the server .(So in short button 1 will turn LED 3 on and button 3 will turn LED4 on).So I added additional characteristic on both server and client, but the problem is I don't know how to check/distinguish whether the incoming request  on the server is which characteristic.

Question

1. How do I inspect the incoming request whether is coming from characteristic 1 or 2 in the server's main.c  led_write_handler function?

Here is the code

static void led_write_handler(uint16_t conn_handle, ble_led_service_t * p_led_service, uint8_t led_state)
{
   //HERE I WANT TO DO IF THE REQUEST IS CHARACTERSIC 1 TURN LED3 AND IF 2 TURN LED 4
     //NRF_LOG_INFO("led handled %d", p_led_service->led_3_char_handles);
    if (led_state)
    {
        bsp_board_led_on(LIGHTBULB_LED3);
        NRF_LOG_INFO("Received LED ON!");
    }
    else
    {
        bsp_board_led_off(LIGHTBULB_LED3);
        NRF_LOG_INFO("Received LED OFF!");
    }
}

[cbd]

Hi,

Assuming that your code uses SDK functions look for the call to characteristic_add().

When the BLE is initialised all services, characteristics, attributes are registered before they can be used. On registration a handle is returned (this allows for the same characteristic type to be used in multiple services).

For example you may have:

 

characteristic_add(p_led_service->service_handle, &add_char, &p_led_service->my_char_button1_handle);


// ... and later

characteristic_add(p_led_service->service_handle, &add_char, &p_led_service->my_char_button2_handle);

p_led_service->my_char_button1_handle is the handle registration data for one characteristic and p_led_service->my_char_button2_handle for the other.

When the BLE event is triggered you'll get some event data and you can check for this (in ble_evt_t parameter) You could pass this into your led_write_handler 

Then you could have:

static void led_write_handler(uint16_t conn_handle, ble_evt_t* p_evt, ble_led_service_t * p_led_service, uint8_t led_state)
{
    ble_gatts_evt_write_t const * p_evt_write = &p_ble_evt->evt.gatts_evt.params.write;
	
	if(p_evt_write->handle == p_led_service->my_button3_handles.value_handle)
    {
		if (led_state)
		{
			bsp_board_led_on(LIGHTBULB_LED3);
			NRF_LOG_INFO("Received LED ON!");
		}
		else
		{
			bsp_board_led_off(LIGHTBULB_LED3);
			NRF_LOG_INFO("Received LED OFF!");
		}
	}
}

Personally, I wouldn't use multiple characteritics for this. You have at least 20 bytes in each characteristic to play with, so why not use just the one characteristic and pass led number as well as led state? Then your handler can be passed both values and the code becomes simpler.

[davidm]

Thank you @cbd I tried to inspect the handle on an incoming request, but regardless which button I press I keep getting value 16 in the log (shown below),I was expecting value 16 for button1 and 19 for button3(at least different value for each button.) What am I doing wrong?

static void led_write_handler(uint16_t conn_handle,ble_evt_t* p_evt, ble_led_service_t * p_led_service, uint8_t led_state)
{
 ble_gatts_evt_write_t const * p_evt_write = &p_evt->evt.gatts_evt.params.write;
     NRF_LOG_INFO("Value Handle %d",p_evt_write->handle);//This prints 16 for both button1 and bnutton3
 
    if (led_state)
    {
        bsp_board_led_on(LIGHTBULB_LED3);
        NRF_LOG_INFO("Received LED ON!");
    }
    else
    {
        bsp_board_led_off(LIGHTBULB_LED3);
        NRF_LOG_INFO("Received LED OFF!");
    }
}

Below is the code from the Server/Bulb(Note that I have only shared the most important snippets of the application)

Server main.c

static void button_event_handler(uint8_t pin_no, uint8_t button_action)
{
    ret_code_t err_code;

    switch (pin_no)
    {
        case LEDBUTTON_ON_BUTTON_PIN:
            err_code = ble_led_service_led2_setting_send(&m_ble_led_service_client, 1);
            if (err_code != NRF_SUCCESS &&
                err_code != BLE_ERROR_INVALID_CONN_HANDLE &&
                err_code != NRF_ERROR_INVALID_STATE)
            {
                APP_ERROR_CHECK(err_code);
            }
            if (err_code == NRF_SUCCESS)
            {
                NRF_LOG_INFO("LED Service write LED2 state %d", button_action);
            }
            break;

        case LEDBUTTON_OFF_BUTTON_PIN:
            err_code = ble_led_service_led2_setting_send(&m_ble_led_service_client, 0);
            if (err_code != NRF_SUCCESS &&
                err_code != BLE_ERROR_INVALID_CONN_HANDLE &&
                err_code != NRF_ERROR_INVALID_STATE)
            {
                APP_ERROR_CHECK(err_code);
            }
            if (err_code == NRF_SUCCESS)
            {
                NRF_LOG_INFO("LED Service write LED2 state %d", button_action);
            }
            break;

        case LEDBUTTON_ON_BUTTON_PIN3:
            err_code = ble_led_service_led3_setting_send(&m_ble_led_service_client, 1);
            if (err_code != NRF_SUCCESS &&
                err_code != BLE_ERROR_INVALID_CONN_HANDLE &&
                err_code != NRF_ERROR_INVALID_STATE)
            {
                APP_ERROR_CHECK(err_code);
            }
            if (err_code == NRF_SUCCESS)
            {
                NRF_LOG_INFO("LED Service write LED3 state %d", button_action);
            }
            break;

        case LEDBUTTON_OFF_BUTTON_PIN3:
            err_code = ble_led_service_led3_setting_send(&m_ble_led_service_client, 0);
            if (err_code != NRF_SUCCESS &&
                err_code != BLE_ERROR_INVALID_CONN_HANDLE &&
                err_code != NRF_ERROR_INVALID_STATE)
            {
                APP_ERROR_CHECK(err_code);
            }
            if (err_code == NRF_SUCCESS)
            {
                NRF_LOG_INFO("LED Service write LED2 state %d", button_action);
            }
            break;


        default:
            APP_ERROR_HANDLER(pin_no);
            break;
        
    }
}

Led_service_server.c

void ble_led_service_on_db_disc_evt(ble_led_service_client_t * p_ble_led_service_client, ble_db_discovery_evt_t const * p_evt)
{
    // Check if the Led Button Service was discovered.
    if (p_evt->evt_type == BLE_DB_DISCOVERY_COMPLETE &&
        p_evt->params.discovered_db.srv_uuid.uuid == BLE_UUID_LED_SERVICE_UUID &&
        p_evt->params.discovered_db.srv_uuid.type == p_ble_led_service_client->uuid_type)
    {
        ble_led_service_client_evt_t evt;

        evt.evt_type    = BLE_LED_SERVICE_CLIENT_EVT_DISCOVERY_COMPLETE;
        evt.conn_handle = p_evt->conn_handle;

        for (uint32_t i = 0; i < p_evt->params.discovered_db.char_count; i++)
        {
            const ble_gatt_db_char_t * p_char = &(p_evt->params.discovered_db.charateristics[i]);
            switch (p_char->characteristic.uuid.uuid)
            {
                case BLE_UUID_LED_2_CHAR_UUID:
                    NRF_LOG_INFO("in case UIID2 ",p_char->characteristic.uuid.uuid);
                    evt.peer_db.led2_handle = p_char->characteristic.handle_value;
                    break;
               case BLE_UUID_LED_3_CHAR_UUID:
                NRF_LOG_INFO("in case UIID3 ",p_char->characteristic.uuid.uuid);
                    evt.peer_db.led3_handle = p_char->characteristic.handle_value;
                    break;

                default:
                    break;
            }
        }

        NRF_LOG_DEBUG("Led Service discovered at peer.");
        //If the instance has been assigned prior to db_discovery, assign the db_handles
        if (p_ble_led_service_client->conn_handle != BLE_CONN_HANDLE_INVALID)
        {
            if (p_ble_led_service_client->peer_led_service_db.led2_handle         == BLE_GATT_HANDLE_INVALID)
            {
                p_ble_led_service_client->peer_led_service_db = evt.peer_db;
            }
             if (p_ble_led_service_client->peer_led_service_db.led3_handle         == BLE_GATT_HANDLE_INVALID)
            {
                p_ble_led_service_client->peer_led_service_db = evt.peer_db;
            }
        }

        p_ble_led_service_client->evt_handler(p_ble_led_service_client, &evt);

    }
}

uint32_t ble_led_service_client_init(ble_led_service_client_t * p_ble_led_service_client, ble_led_service_client_init_t * p_ble_led_service_client_init)
{
    uint32_t      err_code;
    ble_uuid_t    led_service_uuid;
    ble_uuid128_t led_service_base_uuid = {BLE_UUID_LED_SERVICE_BASE_UUID};

    VERIFY_PARAM_NOT_NULL(p_ble_led_service_client);
    VERIFY_PARAM_NOT_NULL(p_ble_led_service_client_init);
    VERIFY_PARAM_NOT_NULL(p_ble_led_service_client_init->evt_handler);

    p_ble_led_service_client->peer_led_service_db.led2_handle   = BLE_GATT_HANDLE_INVALID;
    p_ble_led_service_client->peer_led_service_db.led3_handle   = BLE_GATT_HANDLE_INVALID;
    p_ble_led_service_client->conn_handle                      = BLE_CONN_HANDLE_INVALID;
    p_ble_led_service_client->evt_handler                      = p_ble_led_service_client_init->evt_handler;

    err_code = sd_ble_uuid_vs_add(&led_service_base_uuid, &p_ble_led_service_client->uuid_type);
    if (err_code != NRF_SUCCESS)
    {
        return err_code;
    }
    VERIFY_SUCCESS(err_code);

    led_service_uuid.type = p_ble_led_service_client->uuid_type;
    led_service_uuid.uuid = BLE_UUID_LED_SERVICE_UUID;

    return ble_db_discovery_evt_register(&led_service_uuid);
}


uint32_t ble_led_service_led2_setting_send(ble_led_service_client_t * p_ble_led_service_client, uint8_t status)
{
    VERIFY_PARAM_NOT_NULL(p_ble_led_service_client);

    if (p_ble_led_service_client->conn_handle == BLE_CONN_HANDLE_INVALID)
    {
        return NRF_ERROR_INVALID_STATE;
    }

    NRF_LOG_DEBUG("writing LED2 status 0x%x", status);
  

    tx_message_t * p_msg;

    p_msg              = &m_tx_buffer[m_tx_insert_index++];
    m_tx_insert_index &= TX_BUFFER_MASK;

    p_msg->req.write_req.gattc_params.handle   = p_ble_led_service_client->peer_led_service_db.led2_handle;
    p_msg->req.write_req.gattc_params.len      = sizeof(status);
    p_msg->req.write_req.gattc_params.p_value  = p_msg->req.write_req.gattc_value;
    p_msg->req.write_req.gattc_params.offset   = 0;
    p_msg->req.write_req.gattc_params.write_op = BLE_GATT_OP_WRITE_CMD;
    p_msg->req.write_req.gattc_value[0]        = status;
    p_msg->conn_handle                         = p_ble_led_service_client->conn_handle;
    p_msg->type                                = WRITE_REQ;

    tx_buffer_process();
    return NRF_SUCCESS;
}

uint32_t ble_led_service_led3_setting_send(ble_led_service_client_t * p_ble_led_service_client, uint8_t status)
{
    VERIFY_PARAM_NOT_NULL(p_ble_led_service_client);

    if (p_ble_led_service_client->conn_handle == BLE_CONN_HANDLE_INVALID)
    {
        return NRF_ERROR_INVALID_STATE;
    }

    NRF_LOG_DEBUG("writing LED3 status 0x%x", status);
    NRF_LOG_DEBUG("CON HANDLE %d", p_ble_led_service_client->conn_handle);

    tx_message_t * p_msg;

    p_msg              = &m_tx_buffer[m_tx_insert_index++];
    m_tx_insert_index &= TX_BUFFER_MASK;

    p_msg->req.write_req.gattc_params.handle   = p_ble_led_service_client->peer_led_service_db.led3_handle;
    p_msg->req.write_req.gattc_params.len      = sizeof(status);
    p_msg->req.write_req.gattc_params.p_value  = p_msg->req.write_req.gattc_value;
    p_msg->req.write_req.gattc_params.offset   = 0;
    p_msg->req.write_req.gattc_params.write_op = BLE_GATT_OP_WRITE_CMD;
    p_msg->req.write_req.gattc_value[0]        = status;
    p_msg->conn_handle                         = p_ble_led_service_client->conn_handle;
    p_msg->type                                = WRITE_REQ;

    tx_buffer_process();
    return NRF_SUCCESS;
}

Led_service_server.h

#define BLE_UUID_LED_SERVICE_BASE_UUID  {0x6C, 0xCE, 0x98, 0x91, 0xB9, 0xB3, 0x11, 0x87, 0x9E, 0x47, 0xF5, 0x67, 0x00, 0x00, 0x4B, 0xE5}

// Service & characteristics UUIDs
#define BLE_UUID_LED_SERVICE_UUID  0x0001
#define BLE_UUID_LED_2_CHAR_UUID   0x0002
#define BLE_UUID_LED_3_CHAR_UUID   0x0003


/**@brief Structure containing the handles related to the LED Button Service found on the peer. */
typedef struct
{
    uint16_t led2_handle;          /**< Handle of the LED characteristic as provided by the SoftDevice. */
    uint16_t led3_handle; 
} led_service_db_t;

/**@brief LED Event structure. */
typedef struct
{
    ble_led_service_client_evt_type_t evt_type;        /**< Type of the event. */
    uint16_t                        conn_handle;     /**< Connection handle on which the event occured.*/
    led_service_db_t         peer_db;         /**< LED Service related handles found on the peer device. This will be filled if the evt_type is @ref BLE_LED_SERVICE_CLIENT_EVT_DISCOVERY_COMPLETE.*/
} ble_led_service_client_evt_t;

// Forward declaration of the ble_led_service_client_t type.
typedef struct ble_led_service_client_s ble_led_service_client_t;


typedef void (* ble_led_service_client_evt_handler_t) (ble_led_service_client_t * p_led_service_client, ble_led_service_client_evt_t * p_evt);

/**@brief LED Service Client structure. */
struct ble_led_service_client_s
{
    uint16_t                              conn_handle;                 /**< Connection handle as provided by the SoftDevice. */
    led_service_db_t                      peer_led_service_db;  /**< Handles related to LED Service on the peer*/
    ble_led_service_client_evt_handler_t  evt_handler;                 /**< Application event handler to be called when there is an event related to the LED service. */
    uint8_t                               uuid_type;                   /**< UUID type. */
};

/**@brief LED Service Client initialization structure. */
typedef struct
{
    ble_led_service_client_evt_handler_t evt_handler;  /**< Event handler to be called by the LED Service Client module whenever there is an event related to the LED Service. */
} ble_led_service_client_init_t;

[davidm]

Thanks cbd The code I shared above is for the server. I did register the Led_2 and Led_3. Here is the code registering led_handles in  led_service_server.c .

static uint32_t led_2_char_add(ble_led_service_t * p_led_service)
{
    ble_gatts_char_md_t char_md;
    ble_gatts_attr_t    attr_char_value;
    ble_gatts_attr_md_t attr_md;
    ble_uuid_t          ble_uuid;

    memset(&char_md, 0, sizeof(char_md));
    memset(&attr_md, 0, sizeof(attr_md));
    memset(&attr_char_value, 0, sizeof(attr_char_value));

    char_md.char_props.read          = 1;
    char_md.char_props.write         = 1;
    char_md.p_char_user_desc         = LED2CharName;
    char_md.char_user_desc_size      = sizeof(LED2CharName);
    char_md.char_user_desc_max_size  = sizeof(LED2CharName);
    char_md.p_char_pf                = NULL;
    char_md.p_user_desc_md           = NULL;
    char_md.p_cccd_md                = NULL;
    char_md.p_sccd_md                = NULL;

    // Define the LED 2 Characteristic UUID
    ble_uuid.type = p_led_service->uuid_type;
    ble_uuid.uuid = BLE_UUID_LED_2_CHAR_UUID;

    // Set permissions on the Characteristic value
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.write_perm);
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.read_perm);

    // Attribute Metadata settings
    attr_md.vloc       = BLE_GATTS_VLOC_STACK;
    attr_md.rd_auth    = 0;
    attr_md.wr_auth    = 0;
    attr_md.vlen       = 0;

    // Attribute Value settings
    attr_char_value.p_uuid       = &ble_uuid;
    attr_char_value.p_attr_md    = &attr_md;
    attr_char_value.init_len     = sizeof(uint8_t);
    attr_char_value.init_offs    = 0;
    attr_char_value.max_len      = sizeof(uint8_t);
    attr_char_value.p_value      = NULL;

    return sd_ble_gatts_characteristic_add(p_led_service->service_handle, &char_md,
                                           &attr_char_value,
                                           &p_led_service->led_2_char_handles);
}

static uint32_t led_3_char_add(ble_led_service_t * p_led_service)
{
    ble_gatts_char_md_t char_md3;
    ble_gatts_attr_t    attr_char_value3;
    ble_gatts_attr_md_t attr_md3;
    ble_uuid_t          ble_uuid3;

    memset(&char_md3, 0, sizeof(char_md3));
    memset(&attr_md3, 0, sizeof(attr_md3));
    memset(&attr_char_value3, 0, sizeof(attr_char_value3));

    char_md3.char_props.read          = 1;
    char_md3.char_props.write         = 1;
    char_md3.p_char_user_desc         = LED3CharName;
    char_md3.char_user_desc_size      = sizeof(LED2CharName);
    char_md3.char_user_desc_max_size  = sizeof(LED2CharName);
    char_md3.p_char_pf                = NULL;
    char_md3.p_user_desc_md           = NULL;
    char_md3.p_cccd_md                = NULL;
    char_md3.p_sccd_md                = NULL;

    // Define the LED 2 Characteristic UUID
    ble_uuid3.type = p_led_service->uuid_type;
    ble_uuid3.uuid = BLE_UUID_LED_3_CHAR_UUID;

    // Set permissions on the Characteristic value
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md3.write_perm);
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md3.read_perm);

    // Attribute Metadata settings
    attr_md3.vloc       = BLE_GATTS_VLOC_STACK;
    attr_md3.rd_auth    = 0;
    attr_md3.wr_auth    = 0;
    attr_md3.vlen       = 0;

    // Attribute Value settings
    attr_char_value3.p_uuid       = &ble_uuid3;
    attr_char_value3.p_attr_md    = &attr_md3;
    attr_char_value3.init_len     = sizeof(uint8_t);
    attr_char_value3.init_offs    = 0;
    attr_char_value3.max_len      = sizeof(uint8_t);
    attr_char_value3.p_value      = NULL;

    return sd_ble_gatts_characteristic_add(p_led_service->service_handle, &char_md3,
                                           &attr_char_value3,
                                           &p_led_service->led_3_char_handles);
}

If you want to see the Client Code(Switch) here is full led_service_client.c

static void tx_buffer_process(void)
{
    if (m_tx_index != m_tx_insert_index)
    {
        uint32_t err_code;

        if (m_tx_buffer[m_tx_index].type == READ_REQ)
        {
            err_code = sd_ble_gattc_read(m_tx_buffer[m_tx_index].conn_handle,
                                         m_tx_buffer[m_tx_index].req.read_handle,
                                         0);
        }
        else
        {
            err_code = sd_ble_gattc_write(m_tx_buffer[m_tx_index].conn_handle,
                                          &m_tx_buffer[m_tx_index].req.write_req.gattc_params);
        }
        if (err_code == NRF_SUCCESS)
        {
            NRF_LOG_DEBUG("SD Read/Write API returns Success..");
            m_tx_index++;
            m_tx_index &= TX_BUFFER_MASK;
        }
        else
        {
            NRF_LOG_DEBUG("SD Read/Write API returns error. This message sending will be "
                "attempted again..");
        }
    }
}


/**@brief Function for handling write response events.
 *
 * @param[in] p_ble_led_service_client Pointer to the Led Service Client structure.
 * @param[in] p_ble_evt                Pointer to the BLE event received.
 */
static void on_write_rsp(ble_led_service_client_t * p_ble_led_service_client, ble_evt_t const * p_ble_evt)
{
    // Check if the event if on the link for this instance
    if (p_ble_led_service_client->conn_handle != p_ble_evt->evt.gattc_evt.conn_handle)
    {
        return;
    }
    // Check if there is any message to be sent across to the peer and send it.
    tx_buffer_process();
}


/**@brief Function for handling Disconnected event received from the SoftDevice.
 *
 * @details This function check if the disconnect event is happening on the link
 *          associated with the current instance of the module, if so it will set its
 *          conn_handle to invalid.
 *
 * @param[in] p_ble_led_service_client Pointer to the Led Service Client structure.
 * @param[in] p_ble_evt                Pointer to the BLE event received.
 */
static void on_disconnected(ble_led_service_client_t * p_ble_led_service_client, ble_evt_t const * p_ble_evt)
{
    if (p_ble_led_service_client->conn_handle == p_ble_evt->evt.gap_evt.conn_handle)
    {
        p_ble_led_service_client->conn_handle                    = BLE_CONN_HANDLE_INVALID;
        p_ble_led_service_client->peer_led_service_db.led2_handle         = BLE_GATT_HANDLE_INVALID;
        p_ble_led_service_client->peer_led_service_db.led3_handle         = BLE_GATT_HANDLE_INVALID;
    }
}


void ble_led_service_on_db_disc_evt(ble_led_service_client_t * p_ble_led_service_client, ble_db_discovery_evt_t const * p_evt)
{
    // Check if the Led Button Service was discovered.
    if (p_evt->evt_type == BLE_DB_DISCOVERY_COMPLETE &&
        p_evt->params.discovered_db.srv_uuid.uuid == BLE_UUID_LED_SERVICE_UUID &&
        p_evt->params.discovered_db.srv_uuid.type == p_ble_led_service_client->uuid_type)
    {
        ble_led_service_client_evt_t evt;

        evt.evt_type    = BLE_LED_SERVICE_CLIENT_EVT_DISCOVERY_COMPLETE;
        evt.conn_handle = p_evt->conn_handle;

        for (uint32_t i = 0; i < p_evt->params.discovered_db.char_count; i++)
        {
            const ble_gatt_db_char_t * p_char = &(p_evt->params.discovered_db.charateristics[i]);
            switch (p_char->characteristic.uuid.uuid)
            {
                case BLE_UUID_LED_2_CHAR_UUID:
                    NRF_LOG_INFO("in case UIID2 ",p_char->characteristic.uuid.uuid);
                    evt.peer_db.led2_handle = p_char->characteristic.handle_value;
                    break;
               case BLE_UUID_LED_3_CHAR_UUID:
                NRF_LOG_INFO("in case UIID3 ",p_char->characteristic.uuid.uuid);
                    evt.peer_db.led3_handle = p_char->characteristic.handle_value;
                    break;

                default:
                    break;
            }
        }

        NRF_LOG_DEBUG("Led Service discovered at peer.");
        //If the instance has been assigned prior to db_discovery, assign the db_handles
        if (p_ble_led_service_client->conn_handle != BLE_CONN_HANDLE_INVALID)
        {
            if (p_ble_led_service_client->peer_led_service_db.led2_handle         == BLE_GATT_HANDLE_INVALID)
            {
                p_ble_led_service_client->peer_led_service_db = evt.peer_db;
            }
             if (p_ble_led_service_client->peer_led_service_db.led3_handle         == BLE_GATT_HANDLE_INVALID)
            {
                p_ble_led_service_client->peer_led_service_db = evt.peer_db;
            }
        }

        p_ble_led_service_client->evt_handler(p_ble_led_service_client, &evt);

    }
}


uint32_t ble_led_service_client_init(ble_led_service_client_t * p_ble_led_service_client, ble_led_service_client_init_t * p_ble_led_service_client_init)
{
    uint32_t      err_code;
    ble_uuid_t    led_service_uuid;
    ble_uuid128_t led_service_base_uuid = {BLE_UUID_LED_SERVICE_BASE_UUID};

    VERIFY_PARAM_NOT_NULL(p_ble_led_service_client);
    VERIFY_PARAM_NOT_NULL(p_ble_led_service_client_init);
    VERIFY_PARAM_NOT_NULL(p_ble_led_service_client_init->evt_handler);

    p_ble_led_service_client->peer_led_service_db.led2_handle   = BLE_GATT_HANDLE_INVALID;
    p_ble_led_service_client->peer_led_service_db.led3_handle   = BLE_GATT_HANDLE_INVALID;
    p_ble_led_service_client->conn_handle                      = BLE_CONN_HANDLE_INVALID;
    p_ble_led_service_client->evt_handler                      = p_ble_led_service_client_init->evt_handler;

    err_code = sd_ble_uuid_vs_add(&led_service_base_uuid, &p_ble_led_service_client->uuid_type);
    if (err_code != NRF_SUCCESS)
    {
        return err_code;
    }
    VERIFY_SUCCESS(err_code);

    led_service_uuid.type = p_ble_led_service_client->uuid_type;
    led_service_uuid.uuid = BLE_UUID_LED_SERVICE_UUID;

    return ble_db_discovery_evt_register(&led_service_uuid);
}

void ble_led_service_client_on_ble_evt(ble_evt_t const * p_ble_evt, void * p_context)
{
    if ((p_context == NULL) || (p_ble_evt == NULL))
    {
        return;
    }

    ble_led_service_client_t * p_ble_led_service_client = (ble_led_service_client_t *)p_context;

    switch (p_ble_evt->header.evt_id)
    {
        case BLE_GATTC_EVT_WRITE_RSP:
            on_write_rsp(p_ble_led_service_client, p_ble_evt);
            break;

        case BLE_GAP_EVT_DISCONNECTED:
            on_disconnected(p_ble_led_service_client, p_ble_evt);
            break;

        default:
            break;
    }
}


uint32_t ble_led_service_led2_setting_send(ble_led_service_client_t * p_ble_led_service_client, uint8_t status)
{
    VERIFY_PARAM_NOT_NULL(p_ble_led_service_client);

    if (p_ble_led_service_client->conn_handle == BLE_CONN_HANDLE_INVALID)
    {
        return NRF_ERROR_INVALID_STATE;
    }

    NRF_LOG_DEBUG("writing LED2 status 0x%x", status);
  

    tx_message_t * p_msg;

    p_msg              = &m_tx_buffer[m_tx_insert_index++];
    m_tx_insert_index &= TX_BUFFER_MASK;

    p_msg->req.write_req.gattc_params.handle   = p_ble_led_service_client->peer_led_service_db.led2_handle;
    p_msg->req.write_req.gattc_params.len      = sizeof(status);
    p_msg->req.write_req.gattc_params.p_value  = p_msg->req.write_req.gattc_value;
    p_msg->req.write_req.gattc_params.offset   = 0;
    p_msg->req.write_req.gattc_params.write_op = BLE_GATT_OP_WRITE_CMD;
    p_msg->req.write_req.gattc_value[0]        = status;
    p_msg->conn_handle                         = p_ble_led_service_client->conn_handle;
    p_msg->type                                = WRITE_REQ;

    tx_buffer_process();
    return NRF_SUCCESS;
}

uint32_t ble_led_service_led3_setting_send(ble_led_service_client_t * p_ble_led_service_client, uint8_t status)
{
    VERIFY_PARAM_NOT_NULL(p_ble_led_service_client);

    if (p_ble_led_service_client->conn_handle == BLE_CONN_HANDLE_INVALID)
    {
        return NRF_ERROR_INVALID_STATE;
    }

    NRF_LOG_DEBUG("writing LED3 status 0x%x", status);
    NRF_LOG_DEBUG("CON HANDLE %d", p_ble_led_service_client->conn_handle);

    tx_message_t * p_msg;

    p_msg              = &m_tx_buffer[m_tx_insert_index++];
    m_tx_insert_index &= TX_BUFFER_MASK;

    p_msg->req.write_req.gattc_params.handle   = p_ble_led_service_client->peer_led_service_db.led3_handle;
    p_msg->req.write_req.gattc_params.len      = sizeof(status);
    p_msg->req.write_req.gattc_params.p_value  = p_msg->req.write_req.gattc_value;
    p_msg->req.write_req.gattc_params.offset   = 0;
    p_msg->req.write_req.gattc_params.write_op = BLE_GATT_OP_WRITE_CMD;
    p_msg->req.write_req.gattc_value[0]        = status;
    p_msg->conn_handle                         = p_ble_led_service_client->conn_handle;
    p_msg->type                                = WRITE_REQ;

    tx_buffer_process();
    return NRF_SUCCESS;
}

uint32_t ble_led_service_client_handles_assign(ble_led_service_client_t    * p_ble_led_service_client,
                                               uint16_t                      conn_handle,
                                               const led_service_db_t      * p_peer_handles)
{
    VERIFY_PARAM_NOT_NULL(p_ble_led_service_client);

    p_ble_led_service_client->conn_handle = conn_handle;
    if (p_peer_handles != NULL)
    {
        p_ble_led_service_client->peer_led_service_db = *p_peer_handles;
    }
    return NRF_SUCCESS;
}

[Simon]

Have you made this work? If not, please tell me, and I will look into it.

[davidm]

Hi Simon ,

No not yet.The issue is only on led_write_handler() of main.c server side, on the led_service_server.c led_write_handler() everything shows up correctly.Below are the full code of main.c and led_service_server.c 

main.c

#include <stdbool.h>
#include <stdint.h>
#include <string.h>

#include "nordic_common.h"
#include "nrf.h"
#include "app_error.h"
#include "ble.h"
#include "ble_hci.h"
#include "ble_srv_common.h"
#include "ble_advdata.h"
#include "ble_advertising.h"
#include "ble_conn_params.h"
#include "nrf_sdh.h"
#include "nrf_sdh_soc.h"
#include "nrf_sdh_ble.h"
#include "app_timer.h"
#include "fds.h"
#include "peer_manager.h"
#include "bsp_btn_ble.h"
#include "sensorsim.h"
#include "ble_conn_state.h"
#include "nrf_ble_gatt.h"
#include "nrf_ble_qwr.h"
#include "nrf_pwr_mgmt.h"

#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"

#include "ble_bas.h"
#include "services/led_service.h"

#include "Battery Level/battery_voltage.h"


#define DEVICE_NAME                     "BLE_Lightbulb"                       /**< Name of device. Will be included in the advertising data. */
#define MANUFACTURER_NAME               "NordicSemiconductor"                   /**< Manufacturer. Will be passed to Device Information Service. */
#define APP_ADV_INTERVAL                300                                     /**< The advertising interval (in units of 0.625 ms. This value corresponds to 187.5 ms). */

// Corresponds to LED2 on the development kit
#define LIGHTBULB_LED                   BSP_BOARD_LED_1                         /**< LED to be toggled with the help of the LED Button Service. */
#define LIGHTBULB_LED3                   BSP_BOARD_LED_2 

#define APP_ADV_DURATION                18000                                   /**< The advertising duration (180 seconds) in units of 10 milliseconds. */
#define APP_BLE_OBSERVER_PRIO           3                                       /**< Application's BLE observer priority. You shouldn't need to modify this value. */
#define APP_BLE_CONN_CFG_TAG            1                                       /**< A tag identifying the SoftDevice BLE configuration. */

#define MIN_CONN_INTERVAL               MSEC_TO_UNITS(100, UNIT_1_25_MS)        /**< Minimum acceptable connection interval (0.1 seconds). */
#define MAX_CONN_INTERVAL               MSEC_TO_UNITS(200, UNIT_1_25_MS)        /**< Maximum acceptable connection interval (0.2 second). */
#define SLAVE_LATENCY                   0                                       /**< Slave latency. */
#define CONN_SUP_TIMEOUT                MSEC_TO_UNITS(4000, UNIT_10_MS)         /**< Connection supervisory timeout (4 seconds). */

#define FIRST_CONN_PARAMS_UPDATE_DELAY  APP_TIMER_TICKS(5000)                   /**< Time from initiating event (connect or start of notification) to first time sd_ble_gap_conn_param_update is called (5 seconds). */
#define NEXT_CONN_PARAMS_UPDATE_DELAY   APP_TIMER_TICKS(30000)                  /**< Time between each call to sd_ble_gap_conn_param_update after the first call (30 seconds). */
#define MAX_CONN_PARAMS_UPDATE_COUNT    3                                       /**< Number of attempts before giving up the connection parameter negotiation. */

#define SEC_PARAM_BOND                  1                                       /**< Perform bonding. */
#define SEC_PARAM_MITM                  0                                       /**< Man In The Middle protection not required. */
#define SEC_PARAM_LESC                  0                                       /**< LE Secure Connections not enabled. */
#define SEC_PARAM_KEYPRESS              0                                       /**< Keypress notifications not enabled. */
#define SEC_PARAM_IO_CAPABILITIES       BLE_GAP_IO_CAPS_NONE                    /**< No I/O capabilities. */
#define SEC_PARAM_OOB                   0                                       /**< Out Of Band data not available. */
#define SEC_PARAM_MIN_KEY_SIZE          7                                       /**< Minimum encryption key size. */
#define SEC_PARAM_MAX_KEY_SIZE          16                                      /**< Maximum encryption key size. */

#define DEAD_BEEF                       0xDEADBEEF                              /**< Value used as error code on stack dump, can be used to identify stack location on stack unwind. */

/**< Battery timer. */
APP_TIMER_DEF(m_battery_timer_id);

#define BATTERY_LEVEL_MEAS_INTERVAL     APP_TIMER_TICKS(30000)                 /**< Battery level measurement interval (ticks). */

NRF_BLE_GATT_DEF(m_gatt);                                                       /**< GATT module instance. */
NRF_BLE_QWR_DEF(m_qwr);                                                         /**< Context for the Queued Write module.*/
BLE_ADVERTISING_DEF(m_advertising);                                             /**< Advertising module instance. */

static uint16_t m_conn_handle = BLE_CONN_HANDLE_INVALID;                        /**< Handle of the current connection. */

static uint8_t m_adv_handle = BLE_GAP_ADV_SET_HANDLE_NOT_SET;                   /**< Advertising handle used to identify an advertising set. */
static uint8_t m_enc_advdata[BLE_GAP_ADV_SET_DATA_SIZE_MAX];                    /**< Buffer for storing an encoded advertising set. */
static uint8_t m_enc_scan_response_data[BLE_GAP_ADV_SET_DATA_SIZE_MAX];         /**< Buffer for storing an encoded scan data. */

/**@brief Struct that contains pointers to the encoded advertising data. */
static ble_gap_adv_data_t m_adv_data =
{
    .adv_data =
    {
        .p_data = m_enc_advdata,
        .len    = BLE_GAP_ADV_SET_DATA_SIZE_MAX
    },
    .scan_rsp_data =
    {
        .p_data = m_enc_scan_response_data,
        .len    = BLE_GAP_ADV_SET_DATA_SIZE_MAX

    }
};

/**< Structure used to identify the battery service. */
BLE_BAS_DEF(m_bas);

/**< Structure used to identify the LED service. */
BLE_LED_SERVICE_DEF(m_led_service);
static void led_write_handler(uint16_t conn_handle, ble_led_service_t * p_led_service, uint8_t led_state);

static void battery_level_meas_timeout_handler(void * p_context);
static void battery_level_update(void);

static ble_uuid_t m_adv_uuids[] =                                               /**< Universally unique service identifiers. */
{
    {BLE_UUID_DEVICE_INFORMATION_SERVICE, BLE_UUID_TYPE_BLE}
};

static void advertising_start();


/**@brief Callback function for asserts in the SoftDevice.
 *
 * @details This function will be called in case of an assert in the SoftDevice.
 *
 * @warning This handler is an example only and does not fit a final product. You need to analyze
 *          how your product is supposed to react in case of Assert.
 * @warning On assert from the SoftDevice, the system can only recover on reset.
 *
 * @param[in] line_num   Line number of the failing ASSERT call.
 * @param[in] file_name  File name of the failing ASSERT call.
 */
void assert_nrf_callback(uint16_t line_num, const uint8_t * p_file_name)
{
    app_error_handler(DEAD_BEEF, line_num, p_file_name);
}

/**@brief Function for the Timer initialization.
 *
 * @details Initializes the timer module. This creates and starts application timers.
 */
static void timers_init(void)
{
    // Initialize timer module.
    ret_code_t err_code = app_timer_init();
    APP_ERROR_CHECK(err_code);
    
    // Create timers.
    err_code = app_timer_create(&m_battery_timer_id,
                                APP_TIMER_MODE_REPEATED,
                                battery_level_meas_timeout_handler);
    APP_ERROR_CHECK(err_code);
}

/**@brief Function for starting application timers.
 */
static void application_timers_start(void)
{
    uint32_t err_code;

    // Start application timers.
    err_code = app_timer_start(m_battery_timer_id, BATTERY_LEVEL_MEAS_INTERVAL, NULL);
    APP_ERROR_CHECK(err_code);
}

/**@brief Function for the GAP initialization.
 *
 * @details This function sets up all the necessary GAP (Generic Access Profile) parameters of the
 *          device including the device name, appearance, and the preferred connection parameters.
 */
static void gap_params_init(void)
{
    ret_code_t              err_code;
    ble_gap_conn_params_t   gap_conn_params;
    ble_gap_conn_sec_mode_t sec_mode;

    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&sec_mode);

    err_code = sd_ble_gap_device_name_set(&sec_mode,
                                          (const uint8_t *)DEVICE_NAME,
                                          strlen(DEVICE_NAME));
    APP_ERROR_CHECK(err_code);

    err_code = sd_ble_gap_appearance_set(BLE_APPEARANCE_UNKNOWN);
    APP_ERROR_CHECK(err_code);

    memset(&gap_conn_params, 0, sizeof(gap_conn_params));

    gap_conn_params.min_conn_interval = MIN_CONN_INTERVAL;
    gap_conn_params.max_conn_interval = MAX_CONN_INTERVAL;
    gap_conn_params.slave_latency     = SLAVE_LATENCY;
    gap_conn_params.conn_sup_timeout  = CONN_SUP_TIMEOUT;

    err_code = sd_ble_gap_ppcp_set(&gap_conn_params);
    APP_ERROR_CHECK(err_code);
}


/**@brief Function for initializing the GATT module.
 */
static void gatt_init(void)
{
    ret_code_t err_code = nrf_ble_gatt_init(&m_gatt, NULL);
    APP_ERROR_CHECK(err_code);
}


/**@brief Function for handling Queued Write Module errors.
 *
 * @details A pointer to this function will be passed to each service which may need to inform the
 *          application about an error.
 *
 * @param[in]   nrf_error   Error code containing information about what went wrong.
 */
static void nrf_qwr_error_handler(uint32_t nrf_error)
{
    APP_ERROR_HANDLER(nrf_error);
}

/**@brief Function for initializing services that will be used by the application.
 */
static void services_init(void)
{
    uint32_t       err_code;
    ble_bas_init_t bas_init;
    ble_led_service_init_t led_init;

    nrf_ble_qwr_init_t qwr_init = {0};

    // Initialize Queued Write Module.
    qwr_init.error_handler = nrf_qwr_error_handler;

    err_code = nrf_ble_qwr_init(&m_qwr, &qwr_init);
    APP_ERROR_CHECK(err_code);

    // 1. Initialize the LED service
    led_init.led_write_handler = led_write_handler;

    err_code = ble_led_service_init(&m_led_service, &led_init);
    APP_ERROR_CHECK(err_code);

    // 2. Initialize Battery Service.
    memset(&bas_init, 0, sizeof(bas_init));

    // Here the sec level for the Battery Service can be changed/increased.
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&bas_init.battery_level_char_attr_md.cccd_write_perm);
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&bas_init.battery_level_char_attr_md.read_perm);
    BLE_GAP_CONN_SEC_MODE_SET_NO_ACCESS(&bas_init.battery_level_char_attr_md.write_perm);

    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&bas_init.battery_level_report_read_perm);

    bas_init.evt_handler          = NULL;
    bas_init.support_notification = true;
    bas_init.p_report_ref         = NULL;
    bas_init.initial_batt_level   = 100;

    err_code = ble_bas_init(&m_bas, &bas_init);
    APP_ERROR_CHECK(err_code);
}


/**@brief Function for handling the Connection Parameters Module.
 *
 * @details This function will be called for all events in the Connection Parameters Module which
 *          are passed to the application.
 *          @note All this function does is to disconnect. This could have been done by simply
 *                setting the disconnect_on_fail config parameter, but instead we use the event
 *                handler mechanism to demonstrate its use.
 *
 * @param[in] p_evt  Event received from the Connection Parameters Module.
 */
static void on_conn_params_evt(ble_conn_params_evt_t * p_evt)
{
    ret_code_t err_code;

    if (p_evt->evt_type == BLE_CONN_PARAMS_EVT_FAILED)
    {
        err_code = sd_ble_gap_disconnect(m_conn_handle, BLE_HCI_CONN_INTERVAL_UNACCEPTABLE);
        APP_ERROR_CHECK(err_code);
    }
}


/**@brief Function for handling a Connection Parameters error.
 *
 * @param[in] nrf_error  Error code containing information about what went wrong.
 */
static void conn_params_error_handler(uint32_t nrf_error)
{
    APP_ERROR_HANDLER(nrf_error);
}


/**@brief Function for initializing the Connection Parameters module.
 */
static void conn_params_init(void)
{
    ret_code_t             err_code;
    ble_conn_params_init_t cp_init;

    memset(&cp_init, 0, sizeof(cp_init));

    cp_init.p_conn_params                  = NULL;
    cp_init.first_conn_params_update_delay = FIRST_CONN_PARAMS_UPDATE_DELAY;
    cp_init.next_conn_params_update_delay  = NEXT_CONN_PARAMS_UPDATE_DELAY;
    cp_init.max_conn_params_update_count   = MAX_CONN_PARAMS_UPDATE_COUNT;
    cp_init.start_on_notify_cccd_handle    = BLE_GATT_HANDLE_INVALID;
    cp_init.disconnect_on_fail             = false;
    cp_init.evt_handler                    = on_conn_params_evt;
    cp_init.error_handler                  = conn_params_error_handler;

    err_code = ble_conn_params_init(&cp_init);
    APP_ERROR_CHECK(err_code);
}

/**@brief Function for putting the chip into sleep mode.
 *
 * @note This function will not return.
 */
static void sleep_mode_enter(void)
{
    ret_code_t err_code;

    err_code = bsp_indication_set(BSP_INDICATE_IDLE);
    APP_ERROR_CHECK(err_code);

    // Prepare wakeup buttons.
    err_code = bsp_btn_ble_sleep_mode_prepare();
    APP_ERROR_CHECK(err_code);

    // Go to system-off mode (this function will not return; wakeup will cause a reset).
    err_code = sd_power_system_off();
    APP_ERROR_CHECK(err_code);
}

/**@brief Function for handling BLE events.
 *
 * @param[in]   p_ble_evt   Bluetooth stack event.
 * @param[in]   p_context   Unused.
 */
static void ble_evt_handler(ble_evt_t const * p_ble_evt, void * p_context)
{
    ret_code_t err_code = NRF_SUCCESS;

    switch (p_ble_evt->header.evt_id)
    {
        case BLE_GAP_EVT_DISCONNECTED:
            NRF_LOG_INFO("Disconnected.");
            // LED indication will be changed when advertising starts.
            break;

        case BLE_GAP_EVT_CONNECTED:
            NRF_LOG_INFO("Connected.");
            err_code = bsp_indication_set(BSP_INDICATE_CONNECTED);
            APP_ERROR_CHECK(err_code);
            m_conn_handle = p_ble_evt->evt.gap_evt.conn_handle;
            err_code = nrf_ble_qwr_conn_handle_assign(&m_qwr, m_conn_handle);
            APP_ERROR_CHECK(err_code);
            break;

        case BLE_GAP_EVT_SEC_PARAMS_REQUEST:
            // Pairing not supported
            err_code = sd_ble_gap_sec_params_reply(m_conn_handle,
                                                   BLE_GAP_SEC_STATUS_PAIRING_NOT_SUPP,
                                                   NULL,
                                                   NULL);
            APP_ERROR_CHECK(err_code);
            break;


        case BLE_GAP_EVT_PHY_UPDATE_REQUEST:
        {
            NRF_LOG_DEBUG("PHY update request.");
            ble_gap_phys_t const phys =
            {
                .rx_phys = BLE_GAP_PHY_AUTO,
                .tx_phys = BLE_GAP_PHY_AUTO,
            };
            err_code = sd_ble_gap_phy_update(p_ble_evt->evt.gap_evt.conn_handle, &phys);
            APP_ERROR_CHECK(err_code);
        } break;

        case BLE_GATTS_EVT_SYS_ATTR_MISSING:
            // No system attributes have been stored.
            err_code = sd_ble_gatts_sys_attr_set(m_conn_handle, NULL, 0, 0);
            APP_ERROR_CHECK(err_code);
            break;

        case BLE_GATTC_EVT_TIMEOUT:
            // Disconnect on GATT Client timeout event.
            NRF_LOG_DEBUG("GATT Client Timeout.");
            err_code = sd_ble_gap_disconnect(p_ble_evt->evt.gattc_evt.conn_handle,
                                             BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
            APP_ERROR_CHECK(err_code);
            break;

        case BLE_GATTS_EVT_TIMEOUT:
            // Disconnect on GATT Server timeout event.
            NRF_LOG_DEBUG("GATT Server Timeout.");
            err_code = sd_ble_gap_disconnect(p_ble_evt->evt.gatts_evt.conn_handle,
                                             BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
            APP_ERROR_CHECK(err_code);
            break;

        default:
            // No implementation needed.
            break;
    }
}

/**@brief Function for initializing the BLE stack.
 *
 * @details Initializes the SoftDevice and the BLE event interrupt.
 */
static void ble_stack_init(void)
{
    ret_code_t err_code;

    err_code = nrf_sdh_enable_request();
    APP_ERROR_CHECK(err_code);

    // Configure the BLE stack using the default settings.
    // Fetch the start address of the application RAM.
    uint32_t ram_start = 0;
    err_code = nrf_sdh_ble_default_cfg_set(APP_BLE_CONN_CFG_TAG, &ram_start);
    APP_ERROR_CHECK(err_code);

    // Enable BLE stack.
    err_code = nrf_sdh_ble_enable(&ram_start);
    APP_ERROR_CHECK(err_code);

    // Register a handler for BLE events.
    NRF_SDH_BLE_OBSERVER(m_ble_observer, APP_BLE_OBSERVER_PRIO, ble_evt_handler, NULL);
}

/**@brief Function for handling write events to the LED characteristic.
 *
 * @param[in] p_led_service  Instance of LED Service to which the write applies.
 * @param[in] led_state      Written/desired state of the LED.
 */
static void led_write_handler(uint16_t conn_handle, ble_led_service_t * p_led_service, uint8_t led_state)
{
     NRF_LOG_INFO("sevice= %d",p_led_service->uuid_type);
     //NRF_LOG_INFO("led handled %s", p_led_service->led_3_char_handles);
    if (led_state)
    {
        bsp_board_led_on(LIGHTBULB_LED3);
        NRF_LOG_INFO("Received LED ON!");
    }
    else
    {
        bsp_board_led_off(LIGHTBULB_LED3);
        NRF_LOG_INFO("Received LED OFF!");
    }
}

/**@brief Function for handling advertising events.
 *
 * @details This function will be called for advertising events which are passed to the application.
 *
 * @param[in] ble_adv_evt  Advertising event.
 */
static void on_adv_evt(ble_adv_evt_t ble_adv_evt)
{
    ret_code_t err_code;

    switch (ble_adv_evt)
    {
        case BLE_ADV_EVT_FAST:
            NRF_LOG_INFO("Fast advertising.");
            err_code = bsp_indication_set(BSP_INDICATE_ADVERTISING);
            APP_ERROR_CHECK(err_code);
            break;

        case BLE_ADV_EVT_IDLE:
            sleep_mode_enter();
            break;

        default:
            break;
    }
}


/**@brief Function for initializing the Advertising functionality.
 */
static void advertising_init(void)
{
    ret_code_t             err_code;
    ble_advertising_init_t init;

    memset(&init, 0, sizeof(init));

    init.advdata.name_type               = BLE_ADVDATA_FULL_NAME;
    init.advdata.include_appearance      = true;
    init.advdata.flags                   = BLE_GAP_ADV_FLAGS_LE_ONLY_GENERAL_DISC_MODE;
    init.advdata.uuids_complete.uuid_cnt = sizeof(m_adv_uuids) / sizeof(m_adv_uuids[0]);
    init.advdata.uuids_complete.p_uuids  = m_adv_uuids;

    init.config.ble_adv_fast_enabled  = true;
    init.config.ble_adv_fast_interval = APP_ADV_INTERVAL;
    init.config.ble_adv_fast_timeout  = APP_ADV_DURATION;

    init.evt_handler = on_adv_evt;

    err_code = ble_advertising_init(&m_advertising, &init);
    APP_ERROR_CHECK(err_code);

    ble_advertising_conn_cfg_tag_set(&m_advertising, APP_BLE_CONN_CFG_TAG);
}

/**@brief Function for handling events from the BSP module.
 *
 * @param[in]   event   Event generated when button is pressed.
 */
static void bsp_event_handler(bsp_event_t event)
{
    ret_code_t err_code;

    switch (event)
    {
        case BSP_EVENT_SLEEP:
            sleep_mode_enter();
            break; // BSP_EVENT_SLEEP

        case BSP_EVENT_DISCONNECT:
            err_code = sd_ble_gap_disconnect(m_conn_handle,
                                             BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
            if (err_code != NRF_ERROR_INVALID_STATE)
            {
                APP_ERROR_CHECK(err_code);
            }
            break; // BSP_EVENT_DISCONNECT

        case BSP_EVENT_WHITELIST_OFF:
            if (m_conn_handle == BLE_CONN_HANDLE_INVALID)
            {
                err_code = ble_advertising_restart_without_whitelist(&m_advertising);
                if (err_code != NRF_ERROR_INVALID_STATE)
                {
                    APP_ERROR_CHECK(err_code);
                }
            }
            break; // BSP_EVENT_KEY_0

        default:
            break;
    }
}


/**@brief Function for initializing leds.
 *
 * @details Initializes all LEDs used by the application.
 */
static void leds_init()
{
    ret_code_t err_code;
    
    err_code = bsp_init(BSP_INIT_LEDS, bsp_event_handler);
    APP_ERROR_CHECK(err_code);
}


/**@brief Function for initializing the nrf log module.
 */
static void log_init(void)
{
    ret_code_t err_code = NRF_LOG_INIT(NULL);
    APP_ERROR_CHECK(err_code);

    NRF_LOG_DEFAULT_BACKENDS_INIT();
}


/**@brief Function for initializing power management.
 */
static void power_management_init(void)
{
    ret_code_t err_code;
    err_code = nrf_pwr_mgmt_init();
    APP_ERROR_CHECK(err_code);
}


/**@brief Function for handling the idle state (main loop).
 *
 * @details If there is no pending log operation, then sleep until next the next event occurs.
 */
static void idle_state_handle(void)
{
    if (NRF_LOG_PROCESS() == false)
    {
        nrf_pwr_mgmt_run();
    }
}


/**@brief Function for starting advertising.
 */
static void advertising_start()
{
    ret_code_t err_code = ble_advertising_start(&m_advertising, BLE_ADV_MODE_FAST);
    APP_ERROR_CHECK(err_code);
}

/**@brief Function for handling the Battery measurement timer timeout.
 *
 * @details This function will be called each time the battery level measurement timer expires.
 *
 * @param[in] p_context  Pointer used for passing some arbitrary information (context) from the
 *                       app_start_timer() call to the timeout handler.
 */
static void battery_level_meas_timeout_handler(void * p_context)
{
    UNUSED_PARAMETER(p_context);
    NRF_LOG_INFO("Battery Level timeout event");

    // Only send the battery level update if we are connected
    if (m_conn_handle != BLE_CONN_HANDLE_INVALID)
    {
        battery_level_update();
    }
}
/**@brief Function for updating the Battery Level measurement*/
static void battery_level_update(void)
{
    ret_code_t err_code;

    uint8_t  battery_level;
    uint16_t vbatt;              // Variable to hold voltage reading
    battery_voltage_get(&vbatt); // Get new battery voltage

    battery_level = battery_level_in_percent(vbatt);          //Transform the millivolts value into battery level percent.
    printf("ADC result in percent: %d\r\n", battery_level);

    err_code = ble_bas_battery_level_update(&m_bas, battery_level, m_conn_handle);
    if ((err_code != NRF_SUCCESS) &&
        (err_code != NRF_ERROR_INVALID_STATE) &&
        (err_code != NRF_ERROR_RESOURCES) &&
        (err_code != BLE_ERROR_GATTS_SYS_ATTR_MISSING)
       )
    {
        APP_ERROR_HANDLER(err_code);
    }
}

/**@brief Function for application main entry.
 */
int main(void)
{
    bool erase_bonds;

    // Initialize.
    log_init();
    timers_init();
    battery_voltage_init();
    leds_init();
    power_management_init();
    ble_stack_init();
    gap_params_init();
    gatt_init();
    services_init();
    advertising_init();
    conn_params_init();
    application_timers_start();

    // Start execution.
    NRF_LOG_INFO("BLE Lightbulb example started.");
   
    advertising_start();

    // Enter main loop.
    for (;;)
    {
        idle_state_handle();
    }
}

led_service_server.c

#include <string.h>

#include "nrf_log.h"
#include "led_service.h"

static const uint8_t LED2CharName[] = "LED 2";
static const uint8_t LED3CharName[] = "LED 3";

/**@brief Function for handling the Connect event.
 *
 * @param[in]   p_led_service  LED service structure.
 * @param[in]   p_ble_evt      Event received from the BLE stack.
 */
static void on_connect(ble_led_service_t * p_led_service, ble_evt_t const * p_ble_evt)
{
    p_led_service->conn_handle = p_ble_evt->evt.gap_evt.conn_handle;
}

/**@brief Function for handling the Disconnect event.
 *
 * @param[in]   p_bas       LED service structure.
 * @param[in]   p_ble_evt   Event received from the BLE stack.
 */
static void on_disconnect(ble_led_service_t * p_led_service, ble_evt_t const * p_ble_evt)
{
    UNUSED_PARAMETER(p_ble_evt);
    p_led_service->conn_handle = BLE_CONN_HANDLE_INVALID;
}

/**@brief Function for handling the Write event.
 *
 * @param[in] p_led_service   LED Service structure.
 * @param[in] p_ble_evt       Event received from the BLE stack.
 */
static void on_write(ble_led_service_t * p_led_service, ble_evt_t const * p_ble_evt)
{
    ble_gatts_evt_write_t const * p_evt_write = &p_ble_evt->evt.gatts_evt.params.write;
    NRF_LOG_INFO("handle",p_evt_write->handle);

    if (   (p_evt_write->handle == p_led_service->led_2_char_handles.value_handle)
        && (p_evt_write->len == 1)
        && (p_led_service->led_write_handler != NULL))
    {
        p_led_service->led_write_handler(p_ble_evt->evt.gap_evt.conn_handle, p_led_service, p_evt_write->data[0]);
    }

     if (   (p_evt_write->handle == p_led_service->led_3_char_handles.value_handle)
        && (p_evt_write->len == 1)
        && (p_led_service->led_write_handler != NULL))
    {
        p_led_service->led_write_handler(p_ble_evt->evt.gap_evt.conn_handle, p_led_service, p_evt_write->data[0]);
    }
}

/**@brief Function for adding the LED 2 characteristic.
 *
 */
static uint32_t led_2_char_add(ble_led_service_t * p_led_service)
{
    ble_gatts_char_md_t char_md;
    ble_gatts_attr_t    attr_char_value;
    ble_gatts_attr_md_t attr_md;
    ble_uuid_t          ble_uuid;

    memset(&char_md, 0, sizeof(char_md));
    memset(&attr_md, 0, sizeof(attr_md));
    memset(&attr_char_value, 0, sizeof(attr_char_value));

    char_md.char_props.read          = 1;
    char_md.char_props.write         = 1;
    char_md.p_char_user_desc         = LED2CharName;
    char_md.char_user_desc_size      = sizeof(LED2CharName);
    char_md.char_user_desc_max_size  = sizeof(LED2CharName);
    char_md.p_char_pf                = NULL;
    char_md.p_user_desc_md           = NULL;
    char_md.p_cccd_md                = NULL;
    char_md.p_sccd_md                = NULL;

    // Define the LED 2 Characteristic UUID
    ble_uuid.type = p_led_service->uuid_type;
    ble_uuid.uuid = BLE_UUID_LED_2_CHAR_UUID;

    // Set permissions on the Characteristic value
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.write_perm);
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.read_perm);

    // Attribute Metadata settings
    attr_md.vloc       = BLE_GATTS_VLOC_STACK;
    attr_md.rd_auth    = 0;
    attr_md.wr_auth    = 0;
    attr_md.vlen       = 0;

    // Attribute Value settings
    attr_char_value.p_uuid       = &ble_uuid;
    attr_char_value.p_attr_md    = &attr_md;
    attr_char_value.init_len     = sizeof(uint8_t);
    attr_char_value.init_offs    = 0;
    attr_char_value.max_len      = sizeof(uint8_t);
    attr_char_value.p_value      = NULL;

    return sd_ble_gatts_characteristic_add(p_led_service->service_handle, &char_md,
                                           &attr_char_value,
                                           &p_led_service->led_2_char_handles);
}

static uint32_t led_3_char_add(ble_led_service_t * p_led_service)
{
    ble_gatts_char_md_t char_md3;
    ble_gatts_attr_t    attr_char_value3;
    ble_gatts_attr_md_t attr_md3;
    ble_uuid_t          ble_uuid3;

    memset(&char_md3, 0, sizeof(char_md3));
    memset(&attr_md3, 0, sizeof(attr_md3));
    memset(&attr_char_value3, 0, sizeof(attr_char_value3));

    char_md3.char_props.read          = 1;
    char_md3.char_props.write         = 1;
    char_md3.p_char_user_desc         = LED3CharName;
    char_md3.char_user_desc_size      = sizeof(LED2CharName);
    char_md3.char_user_desc_max_size  = sizeof(LED2CharName);
    char_md3.p_char_pf                = NULL;
    char_md3.p_user_desc_md           = NULL;
    char_md3.p_cccd_md                = NULL;
    char_md3.p_sccd_md                = NULL;

    // Define the LED 2 Characteristic UUID
    ble_uuid3.type = p_led_service->uuid_type;
    ble_uuid3.uuid = BLE_UUID_LED_3_CHAR_UUID;

    // Set permissions on the Characteristic value
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md3.write_perm);
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md3.read_perm);

    // Attribute Metadata settings
    attr_md3.vloc       = BLE_GATTS_VLOC_STACK;
    attr_md3.rd_auth    = 0;
    attr_md3.wr_auth    = 0;
    attr_md3.vlen       = 0;

    // Attribute Value settings
    attr_char_value3.p_uuid       = &ble_uuid3;
    attr_char_value3.p_attr_md    = &attr_md3;
    attr_char_value3.init_len     = sizeof(uint8_t);
    attr_char_value3.init_offs    = 0;
    attr_char_value3.max_len      = sizeof(uint8_t);
    attr_char_value3.p_value      = NULL;

    return sd_ble_gatts_characteristic_add(p_led_service->service_handle, &char_md3,
                                           &attr_char_value3,
                                           &p_led_service->led_3_char_handles);
}


uint32_t ble_led_service_init(ble_led_service_t * p_led_service, const ble_led_service_init_t * p_led_service_init)
{
    uint32_t   err_code;
    uint32_t   err_code3;
    ble_uuid_t ble_uuid;

    // Initialize service structure
    p_led_service->conn_handle = BLE_CONN_HANDLE_INVALID;

    // Initialize service structure.
    p_led_service->led_write_handler = p_led_service_init->led_write_handler;

    // Add service UUID
    ble_uuid128_t base_uuid = {BLE_UUID_LED_SERVICE_BASE_UUID};
    err_code = sd_ble_uuid_vs_add(&base_uuid, &p_led_service->uuid_type);
    if (err_code != NRF_SUCCESS)
    {
        return err_code;
    }

    // Set up the UUID for the service (base + service-specific)
    ble_uuid.type = p_led_service->uuid_type;
    ble_uuid.uuid = BLE_UUID_LED_SERVICE_UUID;

    // Set up and add the service
    err_code = sd_ble_gatts_service_add(BLE_GATTS_SRVC_TYPE_PRIMARY, &ble_uuid, &p_led_service->service_handle);
    if (err_code != NRF_SUCCESS)
    {
        return err_code;
    }

    // Add the different characteristics in the service:
    //   Button press characteristic:   E54B0002-67F5-479E-8711-B3B99198CE6C
    err_code = led_2_char_add(p_led_service);
    err_code3 = led_3_char_add(p_led_service);
    if (err_code != NRF_SUCCESS)
    {
        return err_code;
    }

     if (err_code3 != NRF_SUCCESS)
    {
        return err_code3;
    }


    return NRF_SUCCESS;
}

void ble_led_service_on_ble_evt(ble_evt_t const * p_ble_evt, void * p_context)
{
    ble_led_service_t * p_led_service = (ble_led_service_t *)p_context;

    switch (p_ble_evt->header.evt_id)
    {
        case BLE_GAP_EVT_CONNECTED:
             NRF_LOG_INFO("ON CONNECTED1 ",p_led_service->led_2_char_handles.value_handle);
            on_connect(p_led_service, p_ble_evt);
            break;

        case BLE_GATTS_EVT_WRITE:
            on_write(p_led_service, p_ble_evt);
            break;

        case BLE_GAP_EVT_DISCONNECTED:
            on_disconnect(p_led_service, p_ble_evt);
            break;

        default:
            // No implementation needed.
            break;
    }
}

[Simon]

The reason you're not able to differentiate which characteristic was written inside led_write_handler(), is because none of the arguments give any information about it. 

The conn_handle and led_state does not tell you which characteristic was written to. You probably thought p_led_service would help you check what characteristic was written to, but this is not the case. It will be the same for both characteristics. Let me explain why:

• The function ble_led_service_on_ble_evt() is registered through the macro NRF_SDH_BLE_OBSERVER(), and it is associated with a context (the 4'th parameter)
• Each "observer" will then have a unique context associated with it, that is set once when registered
  • e.g. in your case the observer ble_led_service_on_ble_evt() is associated with a structure of type ble_led_service_t (please ask if you don't understand this and want me to elaborate)

One approach to differentiate between the characteristic, could be to check the uuid:

static void on_write(ble_led_service_t * p_led_service, ble_evt_t const * p_ble_evt)
{
    ble_gatts_evt_write_t const * p_evt_write = &p_ble_evt->evt.gatts_evt.params.write;
    
    uint16_t led_uuid = p_evt_write->uuid.uuid;
    
    if(.....){
        //Pass in uuid as an argument and take the appropriate action depending on that
        p_led_service->led_write_handler(p_ble_evt->evt.gap_evt.conn_handle, p_led_service, p_evt_write->data[0], led_uuid);
    }
}

Hope this helps.

Best regards,

Simon

[davidm]

Hi Simon thank you for taking a look.

So it seems like I just need to change the structure of led_write_handler() to accept additional uint16_t  in .h file  right?

[davidm]

Simon ,

I did what you advised but It seems like I am still experiencing the same issue. On main.c led_write_handler() the uuid always prints 65632 when I press button 2 or 3.

But on led_server_service.c on_write() uuid prints correctly 2 for button 2 and 3 for button 3 which are the uuid's I defined. So the issue is still on main.c led_write_handler()

static void led_write_handler(uint16_t conn_handle, ble_led_service_t * p_led_service, uint8_t led_state,uint16_t led_uuid)
{

     NRF_LOG_INFO("led uuid= %d",led_uuid); //Always prints 65632

    if (led_state)
    {
        bsp_board_led_on(LIGHTBULB_LED3);
        NRF_LOG_INFO("Received LED ON!");
    }
    else
    {
        bsp_board_led_off(LIGHTBULB_LED3);
        NRF_LOG_INFO("Received LED OFF!");
    }
}

[Simon]

I managed to make it work (led_write_handler prints correct uuid). Follow these steps exactly to make it work:

• Download SDK 15.3.0 and place it into an appropriate location
• Download the file two_char_leds.rar (which I have provided)
• For the peripheral example
  • Swap <..>two_char_leds\led_periph_server/ble_lbs.c and <..>two_char_leds\led_periph_server/ble_lbs.h with nRF5_SDK_15.3.0_59ac345\components\ble\ble_services\ble_lbs\ble_lbs.c and nRF5_SDK_15.3.0_59ac345\components\ble\ble_services\ble_lbs\ble_lbs.h 
  • Swap <..>\two_char_leds\led_periph_server\main.c with nRF5_SDK_15.3.0_59ac345\examples\ble_peripheral\ble_app_blinky\main.c
• For the central example
  • Swap <..>two_char_leds\led_central_client/ble_lbs_c.c and <..>two_char_leds\led_central_client/ble_lbs_c.h with nRF5_SDK_15.3.0_59ac345\components\ble\ble_services\ble_lbs_c\ble_lbs_c.c and nRF5_SDK_15.3.0_59ac345\components\ble\ble_services\ble_lbs_c\ble_lbs_c.h 
  • Swap <..>\two_char_leds\led_central_client\main.c with nRF5_SDK_15.3.0_59ac345\examples\ble_central\ble_app_blinky_c\main.c
• Connect two nRF52832 DK (that is what I tested with, but it should work with nRF52840 as well) to the computer and build and flash the ble_app_blinky_c example onto one of the boards and the ble_app_blinky example onto the other board
• Press button 1 on the central board, which should turn on/off  led 3 on the peripheral board
• Press button 2 on the central board, which should turn on/off led 4 on the peripheral board

two_char_leds.rar

Best regards,

Simon

[davidm]

Thank you, Simon, for sharing the code and taking the time to help. I am going to compare your code with mine. Right off the bat, I can see your advertising_init implementation is a little different from mine. But I am still continuing to look for discrepancies.

[Simon]

No problem, I'm always happy to help. Hopefully you are able to get to the bottom of it now.

Best regards,

Simon

[cbd]

+1 Simon.

Just back from vacation. I'm glad that things are sorted now.