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   REPLYADDR JL@gct.com   
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   REPLY:  ddedf167   
   PID: SoupGate-Win32 v1.05   
   XPost: sci.electronics.design   
      
   On Tue, 17 Sep 2024 12:16:55 +0800, Sylvia Else    
   wrote:   
      
   >On 17-Sept-24 10:58 am, 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.   
   >>   
   >> https://www.dropbox.com/scl/fi/bbhdy053xsdzv77g0brc5/B-box_Re   
   et_Button_3.jpg?rlkey=40ozzdvczf4z8625u8i081a9b&raw=1   
   >>   
   >> Does that look like it will work? The paranoid customer can pave over   
   >> the two holes, and even the end-plate screws, with an official-looking   
   >> sticker.   
   >>   
   >> Schmitt trigger U3 is unfortunate and likely unnecessary, but it   
   >> insures against a low-probability hazard.   
   >>   
   >   
   >If the board needs to be powered up, rather than just reset, while the   
   >button is pressed, then how does your solution work? If not, then why is   
   >the fact that there are three power supplies relevant?   
   >   
   >Sylvia.   
      
   Asserting BOOT- (or pushing the button on the Pico board) at the end   
   of reset should launch it into boot mode. On the Pico board,   
   asserrting RESET- is done by cycling the power.   
      
   My user might have to remove all three power sources (PoE, 24 volt   
   wart, USB) to force a reset, if we did the boot button like the Pico   
   does.   
      
   --- SoupGate-Win32 v1.05   
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