How can I disable secure boot on LPC55S69 after I've enabled it?

cp1 — Sat, 25 Apr 2020 18:22:25 GMT

I've been closely following AN12283 and the chip reference manual. I am trying to evaluate secure boot on my LPCXpresso55S69.

I made the mistake of enabling secure boot through the boot ROM before programming a signed image. I used "elftosb-gui" in the 2.7.1 SDK to set secure boot to boot signed images, and then I reset the chip.

Now I can no longer program any flash from the boot rom, or I get "Command disallowed when security is enabled".

I can still access the device and program flash using my JLINK debugger, but it is unable to execute any of the code. I tried programming a signed application with the JLINK, but to no success.

I can see the CMPA page through JLINK/GDB, and I see SECURE_BOOT_CFG == 0x40000000, meaning secure boot is indeed enabled. I have tried numerous times to set SECURE_BOOT_CFG back to 0 using GDB, but none of my writes to CMPA work. Seems CMPA is immutable.

I did not seal any configuration with a sha256 hash, so I was under the impression I could roll back any changes but I haven't figured out how.

Is there anyway I can turn off secure boot and try again? How?

Re: How can I disable secure boot on LPC55S69 after I've enabled it?

ZhangJennie — Mon, 27 Apr 2020 10:22:08 GMT

Conor,

Once secure boot is enabled by setting CMPA, there is no way to disable it. Enabling secure boot is the last step of developing， it's irreversible.

Best Regards

Jun Zhang

topic Re: How can I disable secure boot on LPC55S69 after I've enabled it? in LPC Microcontrollers

How can I disable secure boot on LPC55S69 after I've enabled it?

Re: How can I disable secure boot on LPC55S69 after I've enabled it?