Re: usb 1-3: Product: BBC micro:bit CMSIS-DAP not recognised

[dima.pasechnik@cs.ox.ac.uk]

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On Tue, Dec 20, 2022 at 07:57:28AM +0100, Greg KH wrote:
> On Mon, Dec 19, 2022 at 10:20:48PM +0000, dima.pasechnik@cs.ox.ac.uk wrote:
> > On Mon, Dec 19, 2022 at 07:25:03PM +0100, Greg KH wrote:
> > [...]
> > > 
> > > That is only if you want to manually bind the generic driver to this
> > > device.  The kernel takes this and says "are you sure you want to do
> > > this, if so, email this address and talk to these developers" :)
> > 
> > One does need a dedicated /dev/ttyUSB. It is similar, but not
> > identical, to /dev/ttyACM. Cf. e.g.
> > https://rfc1149.net/blog/2013/03/05/what-is-the-difference-between-devttyusbx-and-devttyacmx/
> 
> Yes, they are a little different and the main point here is your device
> says it is a ACM-compliant device, so just use that tty device node to
> talk to it.  That is the standard for talking serial protocols to USB
> devices.
> 
> By forcing the device to the generic usb-serial driver, you are saying
> "this random endpoint is really a tty pass-through device" is that the
> case?  Why would you have both a ACM and a pass-through set of endpoints
> in the same USB device?
> 
> > And the board makes an effort to establish
> > a dedicated /dev/ttyUSB. Indeed, after I plugged the board in 21:35
> > and did "ls -l /dev/tty*" I saw
> > 
> > crw--w---- 1 root tty       4,  0 Dec 19 21:28 /dev/tty0
> > crw------- 1 dima tty       4,  1 Dec 19 21:35 /dev/tty1
> > crw--w---- 1 root tty       4, 10 Dec 19 21:28 /dev/tty10
> > crw--w---- 1 root tty       4, 11 Dec 19 21:28 /dev/tty11
> 
> Those are not USB-serial devices :)
> 
> Seeing those device nodes is one thing, did you connect to the ttyUSBX
> device nodes and talk to the device properly?
> 
> > Needless to say, there is also /dev/ttyACM0 popping up - so this part
> > of the communication is OK.
> 
> And I think that is the usb-serial connect to this device.
> 
> > I think it's prudent that the kernel understands that it's a
> > a proper ttyUSB device, apparing as /dev/ttyUSB, and advertises it as
> > such. Without it, it's hard to detect it, and indeed, the only way I see
> > this,  without an active usbserial driver, is by the time shown next to 
> > /dev/tty*
> 
> There is no "proper" ttyUSB type of device.  That set of drivers was
> created because there was no USB standard for usb-serial devices way
> back in the day so people made custom chips for them with custom
> protocols.  Then people realized this was a bad thing and came up with
> the USB ACM spec so that you would NOT have to write a custom kernel
> driver for their devices.
> 
> So if this device does need to be controlled by the usb-serial driver,
> what chip is in it and what protocol does it talk?  As Alan said, the
> output of `lsusb -v` for the device would be helpful.
> 
> > > > As you see, no USB serial driver is loaded.
> > > > However, https://tech.microbit.org/software/daplink-interface/
> > > > tells you that there is a 2nd CPU on the board, aka "interface chip",
> > > > capable of UART.
> > > 
> > > And that would be the ttyACM0 device node, right?  Why not use just use that?
> > Actually, the "interface chip" is reponsible not only for ttyACM, but
> > for USB mass storage, and USB serial, all crammed in into the same
> > physical USB port.
> 
> Are there specs on this chip anywhere?
See https://tech.microbit.org/hardware/ 
(choose V2.2X there)
I have nRF52833-QDAA (there is also a different option)

here is "details" on the board itself (describing firmware, I suppose)

# DAPLink Firmware - see https://daplink.io
Build ID: alpha9-189-g5dd23001 (gcc)
Unique ID: 9905360200052833525e24a702a68552000000006e052820
HIC ID: 6e052820
Auto Reset: 1
Automation allowed: 0
Overflow detection: 0
Incompatible image detection: 1
Page erasing: 0
Daplink Mode: Interface
Interface Version: 0256
Bootloader Version: 0256
Git SHA: 5dd23001a7a3199d74870790049d6686e183316c
Local Mods: 0
USB Interfaces: MSD, CDC, HID, WebUSB
Bootloader CRC: 0xa60a7780
Interface CRC: 0x0bac75fa
Remount count: 0
URL: https://microbit.org/device/?id=9905&v=0256


------------------------------------------
Here are the specs for V1 version (not the current, V2 one -these are above) - see my reply
to Alan with lsusb details on this.

https://spivey.oriel.ox.ac.uk/digisys/The_BBC_micro:bit#Microcontroller_chip
https://www.nordicsemi.com/Products/nRF51822

And "details" from the board:

# DAPLink Firmware - see https://mbed.com/daplink
Unique ID: 9901000051114e45005f80130000004e0000000097969901
HIC ID: 97969901
Auto Reset: 1
Automation allowed: 0
Overflow detection: 0
Daplink Mode: Interface
Interface Version: 0249
Bootloader Version: 0243
Git SHA: 9c5fd81e6545d00b7f7c21ca9d8577dbd6a5fed2
Local Mods: 0
USB Interfaces: MSD, CDC, HID, WebUSB
Bootloader CRC: 0x32eb3cfd
Interface CRC: 0xcdb7b2a3
Remount count: 0
URL: https://microbit.org/device/?id=9901&v=0249

HTH
Dima


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