Subj : Re: RP2040 reset idea
To   : tnp@invalid.invalid
From : john larkin
Date : Tue Sep 17 2024 15:33:14

XPost: sci.electronics.design

On Tue, 17 Sep 2024 17:21:36 +0100, The Natural Philosopher
<tnp@invalid.invalid> wrote:

>On 17/09/2024 17:09, john larkin wrote:
>> On Tue, 17 Sep 2024 11:07:17 +0100, The Natural Philosopher
>> <tnp@invalid.invalid> wrote:
>>
>>> On 17/09/2024 03:58, john larkin wrote:
>>>> The RP2040 has a cool mode where it can be made to boot up with the
>>>> USB port looking like a memory stick. That's great for software
>>>> installs or upgrades. The Pico board has a BOOT button on the board;
>>>> if the pico is powered up with the button pushed, it goes into that
>>>> boot mode.
>>>>
>>>> But if I have a product (actually a family of products) in a nice
>>>> aluminum box, a user would have to remove the top cover, remove all
>>>> power sources (there can be three), and hold the button down while
>>>> reconnecting power.
>>>>
>>>> Some of my customers also want to lock a box such that it's impossible
>>>> to write to any nonvolatile memory while it's in a secure area.
>>>>
>>>> So here's an idea: a small hole in the box allows a toothpick or a
>>>> paper clip to push a button. A short push is a regular reset. A long
>>>> push is a memory-stick mode boot. We can have a rotary switch LOCK
>>>> hole too.
>>>>
>>> Thats' what my PICO powered thermostats have. For the onboard button though
>>> Resetting is done by pulling the power.
>>>
>>> The point is that if you do power up with the button pressed, you wipe
>>> the entire FLASH RAM I think.
>>>
>>
>> My Pi guy verifies that entering boot mode doesn't change the contents
>> of flash. Power cycle and things run like before.
>>
>> You had me worried!
>>
>
>Really?
>
>I guess whenever I entered that mode it was to download fresh code...

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.

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