Re: RP2040 reset idea

On 20 Sep 2024 11:30:13 +0100 (BST), Theo
<theom+news@chiark.greenend.org.uk> wrote:

In comp.sys.raspberry-pi The Natural Philosopher <tnp@invalid.invalid> wrote:

On 19/09/2024 23:09, Lasse Langwadt wrote:

On 9/18/24 00:33, john larkin wrote:

 

It looks like a USB memory stick. You can delete or add files if you
want.
>
It boots CPU 0 (the one we call Alice) from a file with the extension
.UL2
>
Why   .UL2   one wonders.
>
We'll put a bunch of files into the flash. Code for Bob, the 2nd CPU.
An FPGA bitstream file. A prototype calibration table. A README file
to explain everything in plain English.

 
sure it's not UF2?
 
https://github.com/microsoft/uf2
 
 

Definitely uf2 here.
 
And no, you cannot 'delete or add files' to it.
The action of pretending to download a uf2 file into what appears to be
an empty drive, erases everything on it and programs the flash.
 
There are no visible files to delete.

>
Neat.  So basically you throw some files at it, which causes a series of
block writes.  UF2 picks out specially tagged block writes and uses that to
program the flash.  It doesn't actually care what other stuff is written to
the flash as it ignores all of that, so it doesn't care about all the FAT
stuff or whatever junk your OS decides to put on there.
>
Means you can write any kind of files to it and it'll only pay attention to
the specific tagged blocks.  If the OS is happy to cache the medium (as many
do) you could maybe even reformat it as some other filesystem like NTFS and
it would still handle writing the UF2 file correctly.
>
Theo

My Pi guy says that you can only write one file, and the act of
writing that file wipes anything that was there before. So the flash
probably doesn't have a file structure, and the USB memory-stick write
is, well, a sort of cheap trick.

That's workable, if inelegant. We can pack everything we need into
that one big file and users can upgrade box code in the field pretty
easily.