PCA10056 can not upgrade with UART

[hank@wy]

Hi,

I use example nRF5SDKforThreadandZigbeev3209fade31\examples\dfu\secure_bootloader\pca10056_uart to upgrade bootloader and coordinator application.

I try to upgarde PCA10056 with 'nrfutil -v -v -v -v dfu serial -pkg boot_uart_ok_arm_0F.zip -p COM20 -t 5', but I must connect computer BOTH with COM20(USB serial port) and COM4(PCA10056 UART) . if I only connect one COM PORT (COM20 OR COM4), it can't upgrade success.

my question is can I upgarde DFU only use COM4 ? and what I need to do?

regards,

[Hung Bui]

Hi, 

Could you give the log when it not successful ? (and also when it's successful) 

What do you have on COM20 ? 
Are you connecting 2 PCA10056 to the PC ?