How to collect value from multiple characteristics in the client?

RE: How to collect value from multiple characteristics in the client?

Taoyi — Tue, 10 Mar 2020 14:28:31 GMT

I have already solved this. Thank you!

RE: How to collect value from multiple characteristics in the client?

tesc — Tue, 10 Mar 2020 14:22:16 GMT

Hi,

What error code do you get, and from what function call? (It sounds like it is from ble_eeg_ch4_c_tx_notif_enable(), can you confirm or correct that assumption?) This will usually point towards what kind of error you are seeing.

Regards,
Terje

RE: How to collect value from multiple characteristics in the client?

tesc — Tue, 10 Mar 2020 14:19:43 GMT

Hi,

I am afraid we only have a peripheral example for the Glucose Service, and we also only provide a library for the server (ble_gls) and not for the client.

Regards,
Terje

RE: How to collect value from multiple characteristics in the client?

Taoyi — Tue, 10 Mar 2020 01:57:32 GMT

Also, I 'm trying to enable 4 notifications after discovering the characteristics. The functions are:

static uint32_t cccd_configure(uint16_t conn_handle, uint16_t cccd_handle, bool enable)
{
    uint8_t buf[BLE_CCCD_VALUE_LEN];
    buf[0] = enable ? BLE_GATT_HVX_NOTIFICATION : 0;
    buf[1] = 0;
    ble_gattc_write_params_t const write_params =
    {
        .write_op = BLE_GATT_OP_WRITE_REQ,
        .flags    = BLE_GATT_EXEC_WRITE_FLAG_PREPARED_WRITE,
        .handle   = cccd_handle,
        .offset   = 0,
        .len      = sizeof(buf),
        .p_value  = buf
    };
    return sd_ble_gattc_write(conn_handle, &write_params);
}
//functions of ch1, ch2, ch3, ch4 are same
uint32_t ble_eeg_ch1_c_tx_notif_enable(ble_eeg_uarts_c_t * p_ble_uarts_c)
{
    VERIFY_PARAM_NOT_NULL(p_ble_uarts_c);
    if ( (p_ble_uarts_c->conn_handle == BLE_CONN_HANDLE_INVALID)
       ||(p_ble_uarts_c->handles.eeg_ch1_tx_cccd_handle == BLE_GATT_HANDLE_INVALID)
       )
    {
        return NRF_ERROR_INVALID_STATE;
    }
		
    return cccd_configure(p_ble_uarts_c->conn_handle,p_ble_uarts_c->handles.eeg_ch1_tx_cccd_handle, true);
}
// in the main.c:

static void ble_uarts_c_evt_handler(ble_eeg_uarts_c_t * p_ble_uarts_c, ble_eeg_uarts_c_evt_t const * p_ble_uarts_evt)
{
    ret_code_t err_code;

    switch (p_ble_uarts_evt->evt_type)
    {
        case BLE_UARTS_C_EVT_DISCOVERY_COMPLETE:
            NRF_LOG_INFO("Discovery complete.");
            err_code = ble_uarts_c_handles_assign(p_ble_uarts_c, p_ble_uarts_evt->conn_handle, &p_ble_uarts_evt->handles);
            APP_ERROR_CHECK(err_code);
            //Enable Notify
            err_code = ble_eeg_ch1_c_tx_notif_enable(p_ble_uarts_c);
            APP_ERROR_CHECK(err_code);
			NRF_LOG_INFO("Enabel notification of the Channel 1 Char");
			
			err_code = ble_eeg_ch2_c_tx_notif_enable(p_ble_uarts_c);
            APP_ERROR_CHECK(err_code);
			NRF_LOG_INFO("Enabel notification of the Channel 2 Char");
				
		    err_code = ble_eeg_ch3_c_tx_notif_enable(p_ble_uarts_c);
            APP_ERROR_CHECK(err_code);
			NRF_LOG_INFO("Enabel notification of the Channel 3 Char");
						
			err_code = ble_eeg_ch4_c_tx_notif_enable(p_ble_uarts_c);
            APP_ERROR_CHECK(err_code);
			NRF_LOG_INFO("Enabel notification of the Channel 4 Char");
            NRF_LOG_INFO("Connected to device with EEG Service.");
            break;

        case BLE_UARTS_C_EVT_NUS_TX_EVT:
            uart_chars_print(p_ble_uarts_evt->p_data, p_ble_uarts_evt->data_len);
            break;

        case BLE_UARTS_C_EVT_DISCONNECTED:
            NRF_LOG_INFO("Disconnected.");
            scan_start();
            break;
    }
}

However, when it tries to enable the notifications of ch1~4, it is said there's a fatal error. How to enable these four characteristics correctly?

Thank you!

RE: How to collect value from multiple characteristics in the client?

Taoyi — Sun, 08 Mar 2020 10:29:09 GMT

Thank you for your help!

I noticed that the glucose sensor peripheral example ble_app_gls have two characteristics that need notification/indication in one service. However, I can't find the central example of it. Do you have the central example of it?

RE: How to collect value from multiple characteristics in the client?

tesc — Wed, 04 Mar 2020 10:04:40 GMT

Hi,

In the ble event, the handle in the ble_gattc_evt_hvx_t data structure is the attribute handle which identifies the characteristic. (Not to be confused with the connection handle, which is found in the ble_gattc_evt_t structure that holds the ble_gattc_evt_hvx_t structure in its params.hvx field.)

For examples on how to handle this, please have a look at the client service implementations in <sdk folder>/components/ble/ble_services (the folders ending in "_c"). Typically there is an on_hvx() function that checks the handle, e.g. for the battery service client in ble_bas_c.c:

/**@brief     Function for handling Handle Value Notification received from the SoftDevice.
 *
 * @details   This function handles the Handle Value Notification received from the SoftDevice
 *            and checks whether it is a notification of the Battery Level measurement from the peer. If
 *            it is, this function decodes the battery level measurement and sends it to the
 *            application.
 *
 * @param[in] p_ble_bas_c Pointer to the Battery Service Client structure.
 * @param[in] p_ble_evt   Pointer to the BLE event received.
 */
static void on_hvx(ble_bas_c_t * p_ble_bas_c, ble_evt_t const * p_ble_evt)
{
    // Check if the event is on the link for this instance.
    if (p_ble_bas_c->conn_handle != p_ble_evt->evt.gattc_evt.conn_handle)
    {
        return;
    }
    // Check if this notification is a battery level notification.
    if (p_ble_evt->evt.gattc_evt.params.hvx.handle == p_ble_bas_c->peer_bas_db.bl_handle)
    {
        if (p_ble_evt->evt.gattc_evt.params.hvx.len == 1)
        {
            ble_bas_c_evt_t ble_bas_c_evt;
            ble_bas_c_evt.conn_handle = p_ble_evt->evt.gattc_evt.conn_handle;
            ble_bas_c_evt.evt_type    = BLE_BAS_C_EVT_BATT_NOTIFICATION;

            ble_bas_c_evt.params.battery_level = p_ble_evt->evt.gattc_evt.params.hvx.data[0];

            p_ble_bas_c->evt_handler(p_ble_bas_c, &ble_bas_c_evt);
        }
    }
}

Regards,
Terje