Re: Simpler Question (Re: MCP2221 I2C/UART to USB)

On 11/13/24 17:35, Tomek CEDRO wrote:
> On Wed, Nov 13, 2024 at 9:30 PM George Mitchell <george+freebsd@m5p.com> wrote:
>> On 11/12/24 17:46, George Mitchell wrote:
>>> Has anyone ever used the MCP2221 chip from Microchip Technology (or any
>>> device incorporating it) on FreeBSD?  If so, does it attach as both a
>>> serial port (cuaUn) AND human interface (uhidn), or just one?  Does it
>>> work well?  Thanks for any information you can give me.       -- George
>>
>> Does FreeBSD have the concept of one hardware device attaching as two
>> device nodes?                                                  -- George
> 
> Hey there George :-)
> 
> Yes USB device may expose several interfaces and each one of them may
> use different kernel module / subsystem, all over single USB cable,
> that works well on FreeBSD. For instance Debug Probes (i.e. DAPLink or
> STLink) offer Serial Port for console access, JTAG/SWD/CMSIS HID
> interface for debug, and UMS (mass storage) emulation for
> drag-and-drop bin file for firmware flashing :-)
> 
> I cannot tell if MCP2221 works well because I did not play with that
> chip you have to verify in practice sorry.. but it seems something
> like FT2232 or CH3421 right? I can see 3 options here depending on
> what you need :-)
> 
> 1. The serial port emulation uses CDC standard, the same with anything
> that goes over HID, UMS, and others that are supported here. If this
> is a generic implementation it should work out of the box.. the only
> thing here that _may_ need an update is the VID:PID pair for a new
> chip identification numbers to be added to a specific kernel driver so
> it attaches on device connect (i.e. CDC so /dev/cuaU* is showed up).
> 
> 2. If this is some sort of custom implementation (like FT2232) then
> additional driver would be necessary to translate between device
> internal registers to something that i.e. CDC can talk with. This is
> the case when you want to have native OS driver because of reasons.
> 
> 3. FreeBSD provides native LibUSB interface that can be used by any
> application that already can talk to the chip directly over LibUSB
> (i.e. PyMCP2221A [1]). No system drivers are necessary in that case.
> For example if the chip is not supported at all here by the system but
> you have application that can talk to the chip on its own over libusb
> all should work fine :-)
> 
> https://github.com/nonNoise/PyMCP2221A
> 
> There are standard tools on FreeBSD like usbconfig that allows you to
> work with USB subsystem and devices (i.e. view usb device descriptors,
> reset, configure interfaces, etc), or devd that allows you to tell
> what system should do on device attach/detach events. USB stack is
> rock solid :-)
> 
> https://man.freebsd.org/cgi/man.cgi?usbconfig
> 
> I hope that helps a bit :-)
> Tomek

It does!  Thank you.                                        -- George
>