bootloader_secure_serial resetting device when starting to write application image

[Hubert Mayer]

He guys,

I'm currently trying to run the secure serial bootloader sample on our hardware which is based on the nrf52832, but the sample code resets the device when starting to write the application image. See Line 55: 0> <debug> nrf_dfu_settings: nrf_fstorage_write(addr=0x00023000, len=0x80 bytes), queue usage: 1<info> nrf_sdh: Inside main in RTT output.

I use the ble_app_buttonless_dfu_without_bonds_s132.zip sample archive with nrfutil.

Output from RTT Viewer: test.log

Output from Windows PowerShell: PS_output.txt

In order for the sample to run on our hardware I had to modify the following files:

• main.c
• nrf_serial_dfu.c
• Makefile

We use different GPIOs for the UART interface and disabled flow control. The UART is connected to a SP3491 (Full-Duplex RS485 Transceiver). Pin 17 and 19 are used as receiver cutput enable and driver output enable and configured via nrf_drv_gpiote in serial_dfu_transport_init.

Am I doing something wrong? Any hints appreciated!

[Hubert Mayer]

By a lot of trial and error I found out that the problem seems to originate from disabling flow control. This knowledge led me to the following thread: How to merge serial and BLE DFU without flow control? which provided me with a workaround. Decreasing the baudrate to 9600 seems to do the trick and the transfer can be completed successfully.