Multiple Characteristics and Notifications

[Sebastian]

Hi Forum,

i've started the development of an custom service on a nrf51822 with s110. The Service contains 4 Characteristics where notifications are enabled.

At the central side i use a nrf51822 with s120. On this Device the multilink_central app is running with modifications to my needs.

I can connect to a peer device and also dicover my characteristics. But when i only can set one characteristic to notify. ( enable_notify)

When i try to run this more than one time the software crashes.

Hope you can help me.

Edit: Ive attached the functions where i am stuck.

The Problem is i can only receive one hvx Notification -> last i discovered

static void notif_enable(client_t * p_client)
{
  uint32_t                 err_code;
  ble_gattc_write_params_t write_params;
  uint8_t                  buf[BLE_CCCD_VALUE_LEN];
     
  printf("In Notify Enable \r\n");

  p_client->state = STATE_NOTIF_ENABLE;

  buf[0] = BLE_GATT_HVX_NOTIFICATION;
  buf[1] = 0;

  write_params.write_op = BLE_GATT_OP_WRITE_REQ;
  write_params.handle   = p_client->srv_db.services[0].charateristics[p_client->char_index].cccd_handle;
  write_params.offset   = 0;
  write_params.len      = sizeof(buf);
  write_params.p_value  = buf;

  err_code = sd_ble_gattc_write(p_client->srv_db.conn_handle, &write_params);
  printf("Error Code: %i",err_code);
  //sd_app_evt_wait();
  wait(200000);
  APP_ERROR_CHECK(err_code);


}


static void db_discovery_evt_handler(ble_db_discovery_evt_t * p_evt)
{
  // Find the client using the connection handle.
  client_t * p_client;
  uint32_t   index;
  bool       is_valid_srv_found = false;

  index = client_find(p_evt->conn_handle);
  p_client = &m_client[index];

  if (p_evt->evt_type == BLE_DB_DISCOVERY_COMPLETE)
  {
    uint8_t i;

    printf("Characteritics found: %i\r\n",p_evt->params.discovered_db.char_count);
    for (i = 0; i <= p_evt->params.discovered_db.char_count; i++)
    {
        ble_db_discovery_char_t * p_characteristic;

        p_characteristic = &(p_evt->params.discovered_db.charateristics[i]);
        printf("UUID: %x ",p_characteristic->characteristic.uuid.uuid);
        if ((p_characteristic->characteristic.uuid.uuid == TEXMESSBOX_PERIPHERAL_CHANNEL_1_UUID)
            &&
            (p_characteristic->characteristic.uuid.type == m_base_uuid_type))
        {
            // Characteristic found. Store the information needed and break.
    	printf("Texxmessbox Channel 1\r\n");
            p_client->char_index = i;
            is_valid_srv_found   = true;

            //break;
        }
        if ((p_characteristic->characteristic.uuid.uuid == TEXMESSBOX_PERIPHERAL_CHANNEL_2_UUID)
                        &&
                        (p_characteristic->characteristic.uuid.type == m_base_uuid_type))
                    {
                        // Characteristic found. Store the information needed and break.
    	printf("Texxmessbox Channel 2\r\n");
                        p_client->char_index = i;
                        is_valid_srv_found   = true;

                        //break;
                    }
        if ((p_characteristic->characteristic.uuid.uuid == TEXMESSBOX_PERIPHERAL_CHANNEL_3_UUID)
                                    &&
                                    (p_characteristic->characteristic.uuid.type == m_base_uuid_type))
                                {
                                    // Characteristic found. Store the information needed and break.
                	printf("Texxmessbox Channel 3\r\n");
                                    p_client->char_index = i;
                                    is_valid_srv_found   = true;
                                    //break;
                                }
        if ((p_characteristic->characteristic.uuid.uuid == TEXMESSBOX_PERIPHERAL_CHANNEL_4_UUID)
                                    &&
                                    (p_characteristic->characteristic.uuid.type == m_base_uuid_type))
                                {
                                    // Characteristic found. Store the information needed and break.
                	printf("Texxmessbox Channel 4\r\n");
                                    p_client->char_index = i;
                                    is_valid_srv_found   = true;
                                    //break;
                                }
    }
}

if (is_valid_srv_found)
{
  // Enable notification.
  printf("Enable Notification\r\n");
  notif_enable(p_client);
}
else
{
    printf("Error\r\n");
    p_client->state = STATE_ERROR;
  }

}

[Sebastian]

First: Thank you for your quick answer. Second: When i try this with a for loop

for(uint8_t i = 0; i < p_evt->params.discovered_db.char_count; i++)
{
     write_params.write_op = BLE_GATT_OP_WRITE_REQ;
  write_params.handle   =   p_client->srv_db.services[0].charateristics[i].cccd_handle;
  write_params.offset   = 0;
  write_params.len      = sizeof(buf);
  write_params.p_value  = buf;
  err_code = sd_ble_gattc_write(p_client->srv_db.conn_handle, &write_params);
}

the Program crashes. I ve read in a different thread that i should use

  sd_app_evt_wait();

but Im not shure how to use this.

[Hung Bui]

@Sebastian: The suggestion from Ulrich was correct. It's a write request (write with response), there is no buffer for it so you can only have one write request at a time. Have you managed to make it work ? If you did could you accept the answer from Ulrich ?