Unable to dfu UART

[AP1]

1. Hi i am using nrf52840 sdk ver 17.1.0 in secure bootloader /pca10056_uart_debug

2. I have flashed the dfu uart code without any change 

3. while performing dfu via uart using command prompt cmd  in windows 

nrfutil dfu serial -pkg cad_dfu_package.zip -p COM4 -b 115200

4. Unable to perform dfu it is waiting at 0% ref picture 

NOTE: I have tried with both HWFC enable and disable (Hardware flow control)

 5. Logs :

<info> app: Inside main
<info> app: dfu uart.
<debug> app: In nrf_bootloader_init
<debug> nrf_dfu_settings: Calling nrf_dfu_settings_init()...
<debug> nrf_dfu_flash: Initializing nrf_fstorage_nvmc backend.
<debug> nrf_dfu_settings: Using settings page.
<debug> nrf_dfu_settings: Copying forbidden parts from backup page.
<debug> nrf_dfu_settings: Destination settings are identical to source, write not needed. Skipping.
<info> nrf_dfu_settings: Backing up settings page to address 0xFE000.
<debug> nrf_dfu_settings: Destination settings are identical to source, write not needed. Skipping.
<debug> app: Enter nrf_bootloader_fw_activate
<info> app: No firmware to activate.
<info> app: Boot validation failed. No valid app to boot.
<debug> app: DFU mode because app is not valid.
<info> nrf_bootloader_wdt: WDT is not enabled
<debug> app: in weak nrf_dfu_init_user
<debug> app: timer_stop (0x2000002C)
<debug> app: timer_activate (0x2000002C)
<info> app: Entering DFU mode.
<debug> app: Initializing transports (found: 1)
<debug> nrf_dfu_serial_uart: serial_dfu_transport_init()
<debug> nrf_dfu_serial_uart: serial_dfu_transport_init() completed
<debug> nrf_dfu_flash: Initializing nrf_fstorage_nvmc backend.
<debug> app: Enter main loop

[Susheel Nuguru]

Hi Avinash,

It does not look like there is any issue with your UARt, but it looks like the bootloader does not find any valid firmware to work on based on this log info.

<debug> app: Enter nrf_bootloader_fw_activate
<info> app: No firmware to activate

Try resetting your device manually and see if it still is stuck in this mode.

[AP1]

Hi I have tried with resetting also but still the same 

[Susheel Nuguru]

It looks like all the logs are saying that the device has entered the DFU mode properly but is unable to receive anything on the transport,  UART in this case. Are you sure that the UART pins configured in the bootloader really corresponds to COM3 in your computer? 

Can you disable HWFC on the COM3 by adding "-fc 0" to your nrfutil command and see if the computer is sending the data without waiting for the peer to respond? If there is progress here, then we know that something is wrong on the nRF side UART configuration.