OpenWrt One - celebrating 20 years of OpenWrt

[Chuanhong Guo]

Hi!

On Tue, Jan 9, 2024 at 10:34 PM John Crispin <john at phrozen.org> wrote:
>
>
> On 09.01.24 14:51, Chuanhong Guo wrote:
> > Hi!
> >
> > On Tue, Jan 9, 2024 at 6:52 PM John Crispin <john at phrozen.org> wrote:
> >> [...]
> >> FAQ
> >>
> >> * Why are there are 2 different flash chips?
> >> - the idea is to make the device (almost!) unbrickable and very easy to
> >> recover
> > What about a built-in JTAG probe instead of SPI-NOR+USB-UART?
> > It'll be actually unbrickable instead.
> >
> >> - NAND will hold the main loader (U-Boot) and the Linux image and will
> >> be the default boot device
> >> - NOR will be write-protected by default (with WP jumper available on
> >> the board) and will hold a recovery bootloader (and other essential
> >> data, like Wi-Fi calibration)
> >> - a dedicated boot select switch will allow changing between NOR and NAND
> >> [...]
> >> * What is the purpose of the console USB-C port?
> >> - Holtek UART to USB bridge with CDC-ACM support on USB-C makes the
> >> device ultra easy to communicate with. No extra hardware or drivers will
> >> be required. Android for example has CDC-ACM support enabled by default
> > There are several MCU-based CMSIS-DAP projects out there. They can
> > provide a CDC-ACM serial with a JTAG interface. It may be a bit slow if a
> > USB1.1 MCU is picked, but it should be enough to start a bootloader to
> > unbrick the device.
> >
> > Here's one with USB2.0 Hi-speed interface:
> > https://github.com/cherry-embedded/CherryDAP
> > The Sipeed M0S module used costs 20CNY on Taobao
> > (or 2.81 USD according to google)
>
> we looked into that kind of solution, i felt more accessible for the
> wider audience to use a CDC-ACM chip. flashing using a DAP involves
> knowing what JTAG is and how to use it. the idea is that the NOR uboot
> has a backup copy of the NAND uboot. holding down one of the buttons
> while powering on the device while BOOTSEL is on NOR will auto recover
> the NAND. cannot think of a simpler solution.

My thought was that all the JTAG stuff can live in a script.
But I agree that yours are definitely easier for end user :D

-- 
Regards,
Chuanhong Guo