XPost: sci.electronics.design   
   From: llc@fonz.dk   
      
   On 9/18/24 00:33, john larkin wrote:   
   > On Tue, 17 Sep 2024 17:21:36 +0100, The Natural Philosopher   
   >  wrote:   
   >   
   >> On 17/09/2024 17:09, john larkin wrote:   
   >>> On Tue, 17 Sep 2024 11:07:17 +0100, The Natural Philosopher   
   >>>  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   
      
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