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Path: ...!news.nobody.at!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> Newsgroups: sci.electronics.design,comp.sys.raspberry-pi Subject: Re: RP2040 reset idea Date: Sat, 21 Sep 2024 20:46:52 -0000 (UTC) Organization: A noiseless patient Spider Lines: 142 Message-ID: <vcnbbs$1nt8a$1@dont-email.me> References: <vcbkcl$3evhe$7@dont-email.me> <eaajej9hlmkdb4dbbdafiff63o549dlgas@4ax.com> <vccaag$3je29$4@dont-email.me> <pf0kejtj8b8riu7aa73ma5700o4bj0mr3e@4ax.com> <vci7f7$o1le$1@dont-email.me> <vcjb88$10tfo$5@dont-email.me> <b+f*To1Uz@news.chiark.greenend.org.uk> <jidrej5t93mud6asmgvis4rcetolmqa6ta@4ax.com> <vclv4m$1he37$2@dont-email.me> <6bntejlmcn474a4upiog3rc8seqcqi6e7p@4ax.com> <vcn3a6$1mla1$3@dont-email.me> <057uejd09fhuk7ktcqljburd969bv3vfdc@4ax.com> <vcn82a$1net1$1@dont-email.me> <l39uejlvspoestr2od47ob2klth3m1bf9u@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Injection-Date: Sat, 21 Sep 2024 22:46:52 +0200 (CEST) Injection-Info: dont-email.me; posting-host="947aba7d3fb8a6242fb4700d57d17df1"; logging-data="1832202"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18fn8N5R3lX2TE0HgqikJ+6" User-Agent: NewsTap/5.5 (iPhone/iPod Touch) Cancel-Lock: sha1:2VqB4lWrc7Z0WfnSM+sy8kBkHLM= sha1:fCq+6XO7DkzcYOPHsPfhqXd/gLY= Bytes: 7293 john larkin <JL@gct.com> wrote: > On Sat, 21 Sep 2024 19:50:34 -0000 (UTC), Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> john larkin <JL@gct.com> wrote: >>> On Sat, 21 Sep 2024 19:29:26 +0100, The Natural Philosopher >>> <tnp@invalid.invalid> wrote: >>> >>>> On 21/09/2024 16:08, john larkin wrote: >>>>> On Sat, 21 Sep 2024 09:12:06 +0100, The Natural Philosopher >>>>> <tnp@invalid.invalid> wrote: >>>>> >>>>>> On 20/09/2024 19:00, john larkin wrote: >>>>>>> On 20 Sep 2024 11:30:13 +0100 (BST), Theo >>>>>>> <theom+news@chiark.greenend.org.uk> wrote: >>>>>>> >>>>>>>> In comp.sys.raspberry-pi The Natural Philosopher <tnp@invalid.invalid> wrote: >>>>>>>>> On 19/09/2024 23:09, Lasse Langwadt wrote: >>>>>>>>>> On 9/18/24 00:33, john larkin wrote: >>>>>>>>> >>>>>>>>>>> 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 >>>>>>>>>> >>>>>>>>>> >>>>>>>>> Definitely uf2 here. >>>>>>>>> >>>>>>>>> And no, you cannot 'delete or add files' to it. >>>>>>>>> The action of pretending to download a uf2 file into what appears to be >>>>>>>>> an empty drive, erases everything on it and programs the flash. >>>>>>>>> >>>>>>>>> There are no visible files to delete. >>>>>>>> >>>>>>>> Neat. So basically you throw some files at it, which causes a series of >>>>>>>> block writes. UF2 picks out specially tagged block writes and uses that to >>>>>>>> program the flash. It doesn't actually care what other stuff is written to >>>>>>>> the flash as it ignores all of that, so it doesn't care about all the FAT >>>>>>>> stuff or whatever junk your OS decides to put on there. >>>>>>>> >>>>>>>> Means you can write any kind of files to it and it'll only pay attention to >>>>>>>> the specific tagged blocks. If the OS is happy to cache the medium (as many >>>>>>>> do) you could maybe even reformat it as some other filesystem like NTFS and >>>>>>>> it would still handle writing the UF2 file correctly. >>>>>>>> >>>>>>>> Theo >>>>>>> >>>>>>> My Pi guy says that you can only write one file, and the act of >>>>>>> writing that file wipes anything that was there before. So the flash >>>>>>> probably doesn't have a file structure, and the USB memory-stick write >>>>>>> is, well, a sort of cheap trick. >>>>>>> >>>>>>> That's workable, if inelegant. We can pack everything we need into >>>>>>> that one big file and users can upgrade box code in the field pretty >>>>>>> easily. >>>>>>> >>>>>> >>>>>> It gets nastier if you want to preserve config info across reboots. >>>>>> It is possible to read and write areas of flash from the code, but its >>>>>> no picnic. >>>>>> And it gets wiped when new code is uploaded >>>>>> >>>>>> >>>>>> It is an area I will have to tackle for one project tho. >>>>> >>>>> Yes, writing to flash from the running application is nasty. >>>>> >>>>> We have to calibrate each box. We'll store the prototype calibration >>>>> table inside the big flash image. At factory test, we'll grab that, >>>>> edit it for this particular unit, and save it to a small SPI eeprom >>>>> chip. That costs 24 cents and one chip select pin. >>>>> >>>>> My guy says that there are a few magic integers at the start of the >>>>> UF2 file that identifies it, well, as a UF2 file. That confirms that >>>>> the Pico flash doesn't have a file structure, it just stores one giant >>>>> chunk of stuff starting at the start. >>>>> >>>>> It's Windows who lies about it acting like a USB memory stick that >>>>> stores files. >>>>> >>>>> We did consider saving the real cal table at some fixed physical >>>>> address near the end of the flash , on the theory that nobody will >>>>> ever write a bootable image that big. That might work. >>>>> >>>> That seems to be the case. >>>> >>>> I looked into it enough to see that it would be possible to store NV >>>> data in a high part of the flash. >>>> >>>> I think that the runtime provides access to a memory location that >>>> indicates the end of the uploaded flash image, so in theory flash above >>>> that is free to write, with the proviso it has to be done in large >>>> blocks on specific address boundaries. >>>> >>>> All this is at least Pi Pico specific anyway. >>> >>> We're using the RP2040 chip, so will have a huge flash chip. We will >>> sometimes store an FPGA config file that could be too big for the 2 >>> MByte part on the Pico. >>> >>> >>>> >>>> Will keep me busy through the dark winter days...:-) >>> >>> Storing anything in high flash still has the problem that you can't >>> run flash-cached code while the write is going on, unless you are very >>> careful. >>> >>> >> >> Its good to have a warm relationship with your linker mapfile. ;) >> >> Cheers >> >> Phil Hobbs > > Interrupts might get nasty, demanding swaps into the flash cache when > the flash is busy writing. > > That’s where the mapfile comes in. Assuming that you can update one flash page while updating another, that is. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics