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From: Lasse Langwadt <llc@fonz.dk>
Newsgroups: comp.sys.raspberry-pi,sci.electronics.design
Subject: Re: RP2040 reset idea
Date: Fri, 20 Sep 2024 00:09:43 +0200
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On 9/18/24 00:33, john larkin wrote:
> 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.

sure it's not UF2?

https://github.com/microsoft/uf2