OpenWrt One - celebrating 20 years of OpenWrt

[Chuanhong Guo]

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)

-- 
Regards,
Chuanhong Guo