Entering DFU mode from MCUboot without requiring button press

[aejoe]

Hi all,

Is it possible to enter DFU mode from MCUboot without requiring a button press?

The hardware is an nRF9160-based custom PCB board without any external buttons, running Zephyr+MCUboot.

What I have gathered so far, according to MCUBoot for Zephyr docs:

> Alternatively, MCUboot can wait for a limited time to check if DFU is invoked by receiving an MCUmgr command. Select CONFIG_BOOT_SERIAL_WAIT_FOR_DFU=y to use this mode. CONFIG_BOOT_SERIAL_WAIT_FOR_DFU_TIMEOUT option defines the amount of time in milliseconds the device will wait for the trigger.

suggesting the `CONFIG_BOOT_SERIAL_WAIT_FOR_DFU_TIMEOUT` could add a short boot delay to wait for `mcumgr` to respond, but so far haven't been able to configure it to do what I imagined.

The answer to a similar question in To put device in bootloader mode without pressing button  suggests that it is not possible, and that we'll need to enter DFU mode from the application.

Our concern is that if the running firmware should crash or become unresponsive, we may be unable to do a USB update without opening the sealed device.

Regards,

J

[AHaug]

Hi,

Apologies for the long reply time. This is due to the Easter holidays in Norway which spanned the previous week.

Is it possible to enter DFU mode from MCUboot without requiring a button press?

You could use serial recovery, for instance the cdc acm wait sample in the following sample repository written by a colleague of mine: https://github.com/hellesvik-nordic/samples_for_nrf_connect_sdk/tree/main/bootloader_samples/serial_recovery

This sample should cover what you're quoting from the MCUboot docs.

I also assume you've seen the  Add DFU support to your application guide which is mentioned in the related case you've linked to, but AFAIK this guide does not show how to use the wait functionality. 

Let me know if this answers your questions

Kind regards,
Andreas

[aejoe]

Thanks Andreas, just checking in.  I haven't had a chance to get back on with the development but will definitely give that a look at next opportunity and get back to you.