Bootloader/ DFU options over serial (UART, USB)

[Smart.Enrg]

Hi,

I have following questions with reference to two different bootloader scenarios with my custom nRF52833 board: 

1) UART based: do I absolutely need RTS, CTS for this or just TX, RX will do?

2) Can the native USB port (i.e in nRF52833-DK context - using J3 and Not Interface MCU USB Connector J2)
     be used as bootloader interface?
     As I understand, when we use nrfutil dfu usb-serial command, we still need to pick COM port
   (created by CDC ACM).

Please advise. Thanks.

[Hung Bui]

Hi Ash, 

1) The UART bootloader wasn't really designed for handling non-HWFC. It's because of the bottle neck when it needs to write to flash. Without HWFC the DFU master may overload the bootloader when it's not finished with flash writing. It might work if you change the baudrate to a very low rate, for example 9600bps. But you would need to perform tests and verify that it work. 

2) Yes native USB should work. We have the USB bootloader designed for the nRF52840 dongle that use only the native USB peripheral on the NRF52840. Note that even though we use native USB, the USB emulate a virtual COM port on PC. It's not directly USB protocol that we used. So on top, it's the UART bootloader that use the virtual UART on the USB interface. 

[Smart.Enrg]

Hung Bui said:

Yes native USB should work. We have the USB bootloader designed for the nRF52840 dongle that use only the native USB peripheral on the NRF52840.

Thanks Hung Bui,

Is native USB DFU implementation available for nRF52833 as well, or it's a 840 only feature?

[Hung Bui]

Hi Ash, 
The nRF52833 and the nRF52840 are very similar. It should be quite straight forward to port the example for nRF52840 to nRF52833 ( update header files, update memorie sizes, bootloader flash location).

[Smart.Enrg]

Thanks again Hung Bui,

Hung Bui said:

It should be quite straight forward to port the example for nRF52840 to nRF52833 ( update header files, update memorie sizes, bootloader flash location).

Could you please point me to the nRF52840 example that you are referring to here?

I am using NCS - can't seem to find any under ...\ncs\v1.5.1\nrf\samples\bootloader

Please advise.

[Hung Bui]

Hi Ash, 

I'm sorry that I was assuming you asked about the bootloader in nRF52 SDK not the nRF Connect SDK. 

So for the DFU scenario in nRF Connect SDK: 

1. I don't think RTS CTS when you do DFU with smpsvr. 

2. Yes it's supported, please have a look here: https://devzone.nordicsemi.com/nordic/nrf-connect-sdk-guides/b/software/posts/device-firmware-update-dfu-with-mcuboot-bootloader

You would just need to select nRF52833 in the list of board you use.