DFU over serial UART

[amarin]

Hi, 

I am working on a project with 2 nrf52840 devices. One is the nrf52840 dk, while the other is a custom board with the nrf52840 module. I want to perform a dfu over uart to the custom board, however, the com port has no direct connection to the pc. I am currently connecting it to the nrf52840 DK via UART TX and RX pins. I would prefer to do the dfu without flow control, thus why I have not connected these pins. I have set the baud rate to 9600 and followed the answer given here. I was given the following error:

I have no idea as to why this is happening. The COM port is correct and I can program the bootloader on to both devices. This only occurs if I want to perform a dfu over UART. Any advice on where I should go from here, would be greatly appreciated!

[amarin]

Sorry for not answering the question, but I did connect the board via the DK and have the DK connect to the PC, however, the custom board does not communicate with the PC. I did flash a slightly modified version of the serial_pca10056 example to the custom board and it is transmitting data, however it does not read anything from the PC when it should be reading any key I push on the PC.

[Hung Bui]

Hi, 
You would need to solve the UART connectivity issue before testing with DFU. 
On the DK you may want to flash an application that set the pins to INPUT, disconnect buffer. It's equivalent to high impedance mode. You set this so that it would not interfere with the communication between the PC and the custom board. 
Next you would need to use a logic analyzer to check if the signal on the UART pins are as expected. 
Please take a photo of your set-up.