Developing a custom bootloader

RE: Developing a custom bootloader

Marjeris Romero — Wed, 20 Oct 2021 08:34:49 GMT

Thanks for your update!

RE: Developing a custom bootloader

Norbert — Fri, 15 Oct 2021 11:10:48 GMT

Hi,

Just to give some final feedback and maybe clues to other people intending to do something similar. I got my bootloader apparently working, even though I do not have an application yet which is fit to run.

The document Bootloader_External_Flash_Modifications.pdf (/cfs-file/__key/communityserver-discussions-components-files/4/Bootloader_5F00_External_5F00_Flash_5F00_Modifications.pdf) is pure gold. A couple of points to watch out for:

Choose a suitable format for the file containing the firmware you want to install. You need to have access to the init record while the bootloader is running. I modified the pc_nrfutil script to be able to write a stream of instructions to a file. This way, the bootloader has everything it needs, even to do the block CRC verification on-the-fly.
You might want to install SD and APP at the same time if there is ever an incompatibility between the ones already installed and the new FW package. To handle multiple updates, I commented out the call to nrf_dfu_settings_write_and_backup() in nrf_dfu_req_handler.c and let that part execute after all updates have been performed.

RE: Developing a custom bootloader

Marjeris Romero — Wed, 06 Oct 2021 11:45:20 GMT

Hi Norbert,

[quote user="ngrunert"]This is not quite what I want to achieve. How the image arrives in the external memory does not concern the nRF. I just need to read the image in the bootloader and write it to the internal Flash.[/quote]

I see, if you only one to read from the external flash and write to the internal then it should be easier and you don't need to change pstorage. In your bootloader example you will need to add SPI or QSPI drivers to read the image from the external flash.

Something similar is done in the USB MSC example in nRF5 SDK, where the file system on QSPI memory is manupulated from the application. You can take a look at that: https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.1.0/usbd_msc_example.html

RE: Developing a custom bootloader

Norbert — Mon, 04 Oct 2021 14:38:28 GMT

Hi,

[quote userid="73427" url="~/f/nordic-q-a/79934/developing-a-custom-bootloader/332397#332397"]I am sorry for the late reply.[/quote]

No problem...

I am still fighting with the latest libraries to get access to the external memory so I have not yet touched the core of the bootloader. The nRF52 SDK is fine as I am using an nRF52840.

[quote userid="73427" url="~/f/nordic-q-a/79934/developing-a-custom-bootloader/332397#332397"]Another idea is to replace the pstorage calls in the bootloade[/quote]

This is not quite what I want to achieve. How the image arrives in the external memory does not concern the nRF. I just need to read the image in the bootloader and write it to the internal Flash.

RE: Developing a custom bootloader

Marjeris Romero — Mon, 04 Oct 2021 14:28:22 GMT

Hi,

I am sorry for the late reply. This document refers to nRF5 SDK. Have you come far with your custom bootloader?

Another idea is to replace the pstorage calls in the bootloader, i.e, instead of using pstorage to write it to internal flash you use a function that takes some parametrers but writes to external flash instead. See this thread for more information.

RE: Developing a custom bootloader

Norbert — Thu, 23 Sep 2021 14:10:58 GMT

P.S.: I came across the document Bootloader_External_Flash_Modifications.pdf (/cfs-file/__key/communityserver-discussions-components-files/4/Bootloader_5F00_External_5F00_Flash_5F00_Modifications.pdf) which was an attachment to a forum post. The document looks quite promising even though it is not clear to which SDK version it refers to.