Can nou update Characteristic value

[OLEG_T]

I've created read onle characteristic called "log". In  main.c i try to update it by calling : ulogd_characteristic_update(&m_ulog_service,Log_Data_arr)

But nothing happens, can you solve my issue (p.s. I am new to ble)

void ulogd_characteristic_update(ble_ulog_service_t *p_ulog_service, int32_t *log_data)
{
if (p_ulog_service->conn_handle != BLE_CONN_HANDLE_INVALID)
{
uint16_t len = 10;
ble_gatts_hvx_params_t hvx_params;
memset(&hvx_params, 0, sizeof(hvx_params));

hvx_params.handle = p_ulog_service->ulog_char_handles.value_handle;
hvx_params.type = BLE_GATT_HVX_NOTIFICATION;
hvx_params.offset = 0;
hvx_params.p_len = &len;
hvx_params.p_data = log_data;

sd_ble_gatts_hvx(p_ulog_service->conn_handle, &hvx_params);
}

}

[OLEG_T]

log_service.h

#ifndef LOG_SERVICE_H
#define LOG_SERVICE_H

#include <stdint.h>
#include "boards.h"
#include "ble.h"
#include "ble_srv_common.h"
#include "nrf_sdh_ble.h"

#define BLE_ULOG_SERVICE_BLE_OBSERVER_PRIO 2
#define BLE_ULOG_SERVICE_DEF(_name) \
static ble_ulog_service_t _name; \
NRF_SDH_BLE_OBSERVER(_name ## _obs, \
BLE_ULOG_SERVICE_BLE_OBSERVER_PRIO, \
ble_ulog_service_on_ble_evt, &_name)
// Base UUID: E54B0000-67F5-479E-8711-B3B99198CE6C
#define BLE_UUID_ULOG_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_ULOG_SERVICE_UUID 0xF000
#define BLE_UUID_ULOG_CHAR_UUID 0xF00A
#define BLE_UUID_ULOGTIME_CHAR_UUID 0xF00C
// Forward declaration of the custom_service_t type.
typedef struct ble_ulog_service_s ble_ulog_service_t;
//typedef void (*ble_ulog_service_ulog_write_handler_t) (uint16_t conn_handle, ble_ulog_service_t * p_ulog_service, uint8_t new_state);
typedef void (*ble_ulog_service_ulogtime_write_handler_t) (uint16_t conn_handle, ble_ulog_service_t * p_ulogtime_service, uint8_t* new_state);

typedef struct
{
// ble_ulog_service_ulog_write_handler_t ulog_write_handler;
ble_ulog_service_ulogtime_write_handler_t ulogtime_write_handler; /**< ulogtime */
} ble_ulog_service_init_t;

typedef struct ble_ulog_service_s
{
uint16_t conn_handle;
uint16_t service_handle;
uint8_t uuid_type;
ble_gatts_char_handles_t ulog_char_handles;
ble_gatts_char_handles_t ulogtime_char_handles;
// ble_ulog_service_ulog_write_handler_t ulog_write_handler;
ble_ulog_service_ulogtime_write_handler_t ulogtime_write_handler;

} ble_ulog_service_t;

uint32_t ble_ulog_service_init(ble_ulog_service_t * p_ulog_service, const ble_ulog_service_init_t * p_ulog_service_init);
void ble_ulog_service_on_ble_evt(ble_evt_t const * p_ble_evt, void * p_context);
void ulogd_characteristic_update(ble_ulog_service_t *p_ulog_service, int32_t *log_data);

#endif