How to update the MCUboot in nRF Connect on nRF52840DK

[RAS_ID]

Hi,

I press Button 1 and Reset to put the nRF52840 DK in to DFU mode that is programmed with a immutable bootloader (B0), mcuboot, and application. This works well to update the application (app_update.bin) using mcumgr over USB. However, during the mcuboot update (signed_by_mcuboot_and_b0_s1_image_update.bin), the application area is over-written and the application enters in a infinite loop after reset. I verified the over-write by reading the flash memory using the nRF programmer. 

Since mcumgr doesn't accept an address or slot parameter, I think the DFU mode is initialized with the application address. 

Are there different ways to enter the DFU mode to update the application and to update the mcuboot?

Thanks,

Ram

[Sigurd]

Hi,

 It's the Partition Manager that sets the start address in a multi-image build. See this link for more information: http://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.4.0/nrf/scripts/partition_manager/partition_manager.html

In your build folder, how does partitions_nrf52840dk_nrf52840.yml and pm_nrf52840dk_nrf52840.config look like ?

[RAS_ID]

Hi,

Please find attached pm.config and partition. yml

Is the address a reason for the mcuboot update not working with the programmer?

Thanks,

Ram

[RAS_ID]

Hi,

I think my earlier observation was not correct, and update always happens at offset 0x200.

But, I am not able to update the bootloader using the nRF programmer. This is what I have found while programming the device with the nRF programmer.

1. Build the project and program the device (b0, mcuboot in so and s1, and application). I used merged.hex

2. Build the project without any change, and program the device with _b0_s0 (OR _b0_s1_, OR app_update.hex), no problem.

3. Build the project with a small change (modify a printf statement), and program the device with _b0_s0. The device fails to boot with _b0_s0 but boots with _b0_s1. I have found that the bootloader signature is changed.

4. Program the device with the newly built  app. There is no issue.

What may be the reason the signature of the bootloaders (_b0_s0_ and _b0_s1_) is changed in a built with a small change? I really appreciate your insights.

Thanks,

Ram

[Sigurd]

Hi Ram,

RAS_ID said:

What may be the reason the signature of the bootloaders (_b0_s0_ and _b0_s1_) is changed in a built with a small change?

Did you do a pristine build (e.g. west build with -p argument), or deleted the old build folder, when you build the project with the change(a modified printf statement)? If you are not setting your own CONFIG_SB_SIGNING_KEY_FILE, then the generated debug keys will be used. New debug keys are generated if you delete the build folder, or do a pristine build.

[RAS_ID]

Hi

Thanks your reply!

Yes, I always delete the build directory and do pristine build.

I am not using my own key file to sign the build, and this may be the reason as explained by you. I will use a predefined key file with CONFIG_SB_SIGNIG_KEY_FILE and repeat the test.

Would the sample key file provided with ncs work?

Thanks,

Ram

[RAS_ID]

Hi Sigurdon,

I made the second time build without pristine and without deleting the build directory and used _b0_s0_image_signed.hex to program the bootloader. It worked and printed the new message when put in the DFU mode.  Thank you very much for pointing me to the problem!

However, I am getting build error with  CONFIG_SB_SIGNIG_KEY_FILE.

This is what I put in the blinky's prj.conf file.

CONFIG_SB_SIGNING_KEY_FILE="c:/Users/singhr48/ncs/v1.4.0/bootloader/mcuboot/root-rsa-2048.pem"
CONFIG_SB_PUBLIC_KEY_FILES="c:/Users/singhr48/ncs/v1.4.0/bootloader/mcuboot/enc-rsa2048-pub.pem"

The two .pem files are provided as part of the ncs.

And the build error is

 [150/162] cmd.exe /C "cd /D C:\Users\singhr48\ncs\v1.4.0\zephyr\samples\basic\blinky\build\zephyr && C:\Users\singhr48\ncs\v1.4.0\toolchain\opt\bin\python.exe C:/Users/singhr48/ncs/v1.4.0/nrf/scripts/bootloader/keygen.py --public --in c:/Users/singhr48/ncs/v1.4.0/bootloader/mcuboot/root-rsa-2048.pem --out C:/Users/singhr48/ncs/v1.4.0/zephyr/samples/basic/blinky/build/zephyr/nrf/subsys/bootloader/generated/public.pem"
Traceback (most recent call last):
File "C:/Users/singhr48/ncs/v1.4.0/nrf/scripts/bootloader/keygen.py", line 33, in <module>
sk = SigningKey.from_pem(args.infile.read()) if args.infile else SigningKey.generate(curve=NIST256p)
File "C:\Users\singhr48\ncs\v1.4.0\toolchain\opt\bin\lib\site-packages\ecdsa\keys.py", line 828, in from_pem
privkey_pem = string[string.index(b("-----BEGIN EC PRIVATE KEY-----")):]
ValueError: subsection not found
FAILED: zephyr/nrf/subsys/bootloader/generated/public.pem
cmd.exe /C "cd /D C:\Users\singhr48\ncs\v1.4.0\zephyr\samples\basic\blinky\build\zephyr && C:\Users\singhr48\ncs\v1.4.0\toolchain\opt\bin\python.exe C:/Users/singhr48/ncs/v1.4.0/nrf/scripts/bootloader/keygen.py --public --in c:/Users/singhr48/ncs/v1.4.0/bootloader/mcuboot/root-rsa-2048.pem --out C:/Users/singhr48/ncs/v1.4.0/zephyr/samples/basic/blinky/build/zephyr/nrf/subsys/bootloader/generated/public.pem"
ninja: build stopped: subcommand failed.

Could you please guide what I am missing while defining the key files?

Thanks,

Ram

[Sigurd]

Hi Ram,

Try setting it to the EC key instead.

For me it's:

CONFIG_SB_SIGNING_KEY_FILE="C:/ncs/bootloader/mcuboot/root-ec-p256.pem"

 

I don't think you need to set CONFIG_SB_PUBLIC_KEY_FILES (I think it will be generated based on the private/signing key for you, but if you are setting it manually, it need to generated based on the private key).