How to enable indication and get CCCD value to check

Question

Hi All, 
 I want to use DFU to update the firmware from master to peripheral over BLE , both master and peripheral are nrf52840. My purpose is that the master sends a command to make the peripheral enter bootloader.Therefore I need enable indication and write 0x01 to peripheral. "nrf connect" can do it. 
 
 But the problem is that I don't kown if the indication is enable on peripheral .I referred to other answers but failed becuase I can't excuess sd_ble_gatts_value_get() and sd_ble_gatts_hvx() correctly, my programs are below. 
 //enable indication
static uint32_t cccd_configure(ble_hrs_c_t * p_ble_hrs_c, bool enable)
{
 NRF_LOG_INFO("Configuring CCCD. CCCD Handle = %x, Connection Handle = %x",
 p_ble_hrs_c->peer_hrs_db.hrm_cccd_handle,
 p_ble_hrs_c->conn_handle);

 nrf_ble_gq_req_t hrs_c_req;
 uint8_t cccd[BLE_CCCD_VALUE_LEN];
 uint16_t cccd_val = enable ? BLE_GATT_HVX_INDICATION : 0;

 cccd[0] = LSB_16(cccd_val);
 cccd[1] = MSB_16(cccd_val);

 memset(&hrs_c_req, 0, sizeof(hrs_c_req));

 hrs_c_req.type = NRF_BLE_GQ_REQ_GATTC_WRITE;
 hrs_c_req.error_handler.cb = gatt_error_handler;
 hrs_c_req.error_handler.p_ctx = p_ble_hrs_c;
 hrs_c_req.params.gattc_write.handle = p_ble_hrs_c->peer_hrs_db.hrm_cccd_handle;
 hrs_c_req.params.gattc_write.len = BLE_CCCD_VALUE_LEN;
	hrs_c_req.params.gattc_write.offset = 0;
 hrs_c_req.params.gattc_write.p_value = cccd;
 hrs_c_req.params.gattc_write.write_op = BLE_GATT_OP_WRITE_REQ;
	hrs_c_req.params.gattc_write.flags = BLE_GATT_EXEC_WRITE_FLAG_PREPARED_WRITE;
 return nrf_ble_gq_item_add(p_ble_hrs_c->p_gatt_queue, &hrs_c_req, p_ble_hrs_c->conn_handle);
} 
 ble_hrs_c_handles_assign 
 uint32_t ble_hrs_c_handles_assign(ble_hrs_c_t * p_ble_hrs_c,
 uint16_t conn_handle,
 const hrs_db_t * p_peer_hrs_handles)
{
 VERIFY_PARAM_NOT_NULL(p_ble_hrs_c);

 p_ble_hrs_c->conn_handle = conn_handle;
 if (p_peer_hrs_handles != NULL)
 {
 //p_ble_hrs_c->peer_hrs_db = *p_peer_hrs_handles;
 NRF_LOG_INFO("In handles assign");
 p_ble_hrs_c->peer_hrs_db.hrm_cccd_handle = p_peer_hrs_handles->hrm_cccd_handle;
 p_ble_hrs_c->peer_hrs_db.hrm_handle = p_peer_hrs_handles->hrm_handle;
 }

 return nrf_ble_gq_conn_handle_register(p_ble_hrs_c->p_gatt_queue, conn_handle);
} 
 when find the service and characteristics 
 static void hrs_c_evt_handler(ble_hrs_c_t * p_hrs_c, ble_hrs_c_evt_t * p_hrs_c_evt)
{
	
 ret_code_t err_code;
	bool is_indication_enabled = true;
 switch (p_hrs_c_evt->evt_type)
 {
 case BLE_HRS_C_EVT_DISCOVERY_COMPLETE:
 {
 NRF_LOG_INFO("dfu service discovered.");

 err_code = ble_hrs_c_handles_assign(p_hrs_c,
 p_hrs_c_evt->conn_handle,
 &p_hrs_c_evt->params.peer_db);
 APP_ERROR_CHECK(err_code);

 err_code = cccd_configure(p_hrs_c,true);
 APP_ERROR_CHECK(err_code);
 ble_gatts_value_t gatt_value;
 uint8_t cccd_value;
 gatt_value.len = 2;
 gatt_value.p_value = &cccd_value;
 gatt_value.offset = 0;
 err_code = sd_ble_gatts_value_get(p_hrs_c_evt->conn_handle, p_hrs_c->peer_hrs_db.hrm_cccd_handle, &gatt_value);
 APP_ERROR_CHECK(err_code);
 } break;
 default:
 break;
 }
} 
 connection handle : 0, characteristics handle:0x16, cccd handle:0x17 
 sd_ble_gatts_value_get() returned error 5 
 I have no idea where is wrong , please give me some advice 
 Thanks, 
 Steven

Edvin · Accepted Answer

Try to copy the ble_hrs_c_hrm_norif_enable() function and change it from notification to indication, as I described in the previous reply. 
 If you want to test whether indications are already enabled, please try to read the characteristic description. The HRS example doesn't do this, and I don't think we have any central examples that does this, really. (Probably because it is easier to just enable the indication/notification again, which I recommend). 
 What you need to do to read is to use the implementation from cccd_configure() in ble_hrs_c.c and change NRF_BLE_GQ_REQ_GATTC_WRITE to NRF_BLE_GX_REQ_GATTC_READ, and change all instances of: 
 hrs_c_req.params.gattc_write. ... 
 with 
 hrs_c_req.params.gattc_read. ... 
 This will probably generate an event at a later point in time in your ble_evt_handler: 
 case BLE_GATTC_EVT_READ_RSP: 
 Look at the p_ble_evt->evt.gattc_evt.params.read_rsp struct (ble_gattc_evt_read_rsp_t) to implement this handler. 
 
 BR, 
 Edvin

lolifrog · Answer

Hello Edvin, 
 Thanks for your patient replies this week, I figured out why BLE_GATTS_EVT_HVC event was not generated . 
 Because t he peripheral is responding to the Enter Bootloader request with a handle value indication which should be confirmed by the master. This confirmation will generate the BLE_GATTS_EVT_HVC event. 
 I add the code to send a Handle Value Confirmation to the GATT Server in the master side before on_hvx(): 
 void ble_hrs_c_on_ble_evt(ble_evt_t const * p_ble_evt, void * p_context)
{
 ble_hrs_c_t * p_ble_hrs_c = (ble_hrs_c_t *)p_context;

 if ((p_ble_hrs_c == NULL) || (p_ble_evt == NULL))
 {
 return;
 }

 switch (p_ble_evt->header.evt_id)
 {
 case BLE_GATTC_EVT_HVX:
 //Send a Handle Value Confirmation to the GATT Server
 sd_ble_gattc_hv_confirm(p_ble_evt->evt.common_evt.conn_handle,p_ble_evt->evt.gattc_evt.params.hvx.handle);
 on_hvx(p_ble_hrs_c, p_ble_evt);
 break;

 case BLE_GAP_EVT_DISCONNECTED:
 on_disconnected(p_ble_hrs_c, p_ble_evt);
 break;

 default:
 break;
 }
} 
 Reference： 
 https://devzone.nordicsemi.com/f/nordic-q-a/52470/create-ble_dfu_c---triggering-enter-bootloader-doesn-t-work/211297#211297 
 https://devzone.nordicsemi.com/f/nordic-q-a/22743/no-ble_gatts_evt_hvc-event-generating-when-using-s140-for-bluetooth-5 
 Best regards, 
 Steven

lolifrog · Answer

Edvin said: Yes. Does it return NRF_SUCCESS (0x00)? And do you see the callback later? Yes, the return is NRF_SUCCESS(0x00). I read the value of cccd(0x0002) as you said. However,I met another question: I failed to write 0x01 to the characteristic based on ble_nus_c_string_send() because the peripheral didn't have any logs.But I can read the characteristic (Buttonless DFU without bonds:0x03) : BLE_GATTC_EVT_READ_RSP,len:3 value[0]:20 value[1]:1 value[2]:1 and I change the array from {0x01} to {0x04} , the peripheral has logs as below: app : Request to send a response to client failed. app : Request to enter bootloader mode failed asynchroneously. I can also read the characteristic (Buttonless DFU without bonds:0x03) : BLE_GATTC_EVT_READ_RSP,len:3 value[0]:20 value[1]:4 value[2]:2 Bluetooth master connects to the peripheral periodically(if I don't write a byte to the characteristic, the master will not be disconnected). Logs are below: Disconnected. conn_handle: 0x0, reason: 0x13 When reconnected and written 0x04(if the written byte is 0x01,there is no logs below) ,the peripheral show logs: Request to enter bootloader mode failed asynchroneously I wonder where is wrong? More details: write characteristic: uint32_t ble_dfu_c_string_send(ble_hrs_c_t * p_ble_dfu_c, uint8_t * p_string, uint16_t length) { VERIFY_PARAM_NOT_NULL(p_ble_dfu_c); nrf_ble_gq_req_t write_req; memset(&write_req, 0, sizeof(nrf_ble_gq_req_t)); if (length > NRF_SDH_BLE_GATT_MAX_MTU_SIZE - 3) { NRF_LOG_WARNING("Content too long."); return NRF_ERROR_INVALID_PARAM; } if (p_ble_dfu_c->conn_handle == BLE_CONN_HANDLE_INVALID) { NRF_LOG_WARNING("Connection handle invalid."); return NRF_ERROR_INVALID_STATE; } write_req.type = NRF_BLE_GQ_REQ_GATTC_WRITE; write_req.error_handler.cb = gatt_error_handler; write_req.error_handler.p_ctx = p_ble_dfu_c; write_req.params.gattc_write.handle = p_ble_dfu_c->peer_hrs_db.hrm_handle; write_req.params.gattc_write.len = length; write_req.params.gattc_write.offset = 0; write_req.params.gattc_write.p_value = p_string; write_req.params.gattc_write.write_op = BLE_GATT_OP_WRITE_CMD; NRF_LOG_INFO("ble_dfu_c_string_send write.handle:%x",p_ble_dfu_c->peer_hrs_db.hrm_handle); return nrf_ble_gq_item_add(p_ble_dfu_c->p_gatt_queue, &write_req, p_ble_dfu_c->conn_handle); } read characteristic: uint32_t ble_dfu_ch_read(ble_hrs_c_t * p_ble_dfu_c,uint16_t chara_handle) { VERIFY_PARAM_NOT_NULL(p_ble_dfu_c); nrf_ble_gq_req_t read_req; memset(&read_req, 0, sizeof(nrf_ble_gq_req_t)); if (p_ble_dfu_c->conn_handle == BLE_CONN_HANDLE_INVALID) { NRF_LOG_INFO("Connection handle invalid."); return NRF_ERROR_INVALID_STATE; } NRF_LOG_INFO("In ch_read.handle:%x.",chara_handle); read_req.type = NRF_BLE_GQ_REQ_GATTC_READ; read_req.error_handler.cb = gatt_error_handler; read_req.error_handler.p_ctx = p_ble_dfu_c; read_req.params.gattc_read.handle = chara_handle; read_req.params.gattc_read.offset = 0; return nrf_ble_gq_item_add(p_ble_dfu_c->p_gatt_queue, &read_req, p_ble_dfu_c->conn_handle); } main //uint8_t arr={0x01}, and can be changed by uart err_code = ble_dfu_c_string_send(&m_hrs_c, arr, 1); APP_ERROR_CHECK(err_code); err_code = ble_dfu_ch_read(&m_hrs_c,m_hrs_c.peer_hrs_db.hrm_handle); APP_ERROR_CHECK(err_code); Best regards, Steven

How to enable indication and get CCCD value to check

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