Subj : Re: RP2040 reset idea To : tnp@invalid.invalid From : john larkin Date : Tue Sep 17 2024 07:20:54 XPost: sci.electronics.design 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. If BOOT- is low at the end of reset, it powers up in USB memory stick mode. I don't think that wipes the files stored in the big serial flash. > > >> https://www.dropbox.com/scl/fi/bbhdy053xsdzv77g0brc5/B-box_Reset_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. >At a brief glance, yes, but I donbt see why a simmle disconnect power >switch in addition to the onboard switch wouldn't be as easy. There are three potential power sources to disconnect, and I don't really want a power switch. >> >> Schmitt trigger U3 is unfortunate and likely unnecessary, but it >> insures against a low-probability hazard. >> >Once you start laying out a board, put everything on it you may need, >Can always leave it out later The schmitt adds way under a tenth of a per cent to the board area and the cost, so may as well leave it in. --- SoupGate-Win32 v1.05 * Origin: Agency HUB, Dunedin - New Zealand | Fido<>Usenet Gateway (3:770/3) .