Problem with running BLE DFU example

Question

Dear Nordic, 
 I am trying to run the BLE DFU example code. I followed the steps as instructed in the infocentre infocenter.nordicsemi.com/index.jsp 
 This is the way I followed your instructions, please correct me if I am wrong- 
 Erase the device and flash the softdevice. 
 Go to examples->dfu->bootloader, and flash the dfu_dual_bank_ble code. (LED 1 and 3 glowing indicating advertising and bootloader mode). Advertises as DFUTARG. 
 Copied dfu_test_app_hrm zip file to my android phone. 
 Opened nrf_toolbox,selected the device,selected the zip file and clicked upload. 
 The problem I am facing is that, upload is not happening, its getting connected and disconnected, and gives GATT_INTERNAL_ERROR

arjun · Accepted Answer

The code works properly when using nrfConnect. 
 The problem seemed to in setting the clock source. 
 In pca10040.h, when using clock source as RC oscillator, define parameters as- 
 {.source = NRF_CLOCK_LF_SRC_RC, 
.rc_ctiv = 16, 
.rc_temp_ctiv = 4, 
.xtal_accuracy = NRF_CLOCK_LF_XTAL_ACCURACY_250_PPM} 
 whereas when using external crystal, .rc_temp_ctiv = 0. 
 Also ensured that in hci_mem_pool_internal.h, the parameters are defined as following- 
 TX_BUF_SIZE 4u
RX_BUF_SIZE 32u
RX_BUF_QUEUE_SIZE 8u. 
 However I still can,t figure out, where am I going wrong with nrf_toolbox.while uploading its stucking at 33%. 
 For help with DFU using nrf_connect,
 pcbreflux.blogspot.in/.../nrf51822-secure-dfu-ota-via-ble.html