Example secure bootloader UART not working

[Ryan Lindeman (CAE)]

I am trying to get the example secure bootloader uart working on my nRF52832 development board but I am seeing a lot of TX errors on the RTT log output from the debug version of the bootloader. Thinking it might be related to flow control, I compiled my own version and disabled flow control but that didn't seem to resolve anything.

I captured a Saleae output which seems to show the nrfutil (version 6.1.6) is sending a single valid Ping request but the RTT log seems to indicate TWO Ping requests were processed for unknown reasons. I want to be able to trust my bootloader is going to work so I really need this to be reliable.

Can you please help provide any insights as to what might be going wrong?

[ovrebekk]

Hi Ryan

One possible issue when flashing through JLink CDC is that the mass storage device set up on the same USB interface can interfere with the USB CDC functionality. 

This problem, and a workaround, is described here.

Another thing you can test since you are just using standard development kits is to try the pre compiled bootloader in /nRF5_SDK_17.1.0_ddde560/examples/dfu/secure_dfu_test_images/uart/nrf52832

If you navigate to that folder you can test the DFU by running the following commands:

$ nrfjprog --program bootloader_secure_uart_debug_without_bonds_mbr.hex --chiperase

$ nrfjprog --program mbr.hex -r

$ nrfutil dfu serial -pkg blinky_mbr.zip -p /dev/ttyACM0 -b 115200

Best regards
Torbjørn