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List:       linux-usb
Subject:    Re: Attaching MEGAWIN USB Bridge with USB generic driver
From:       Alan Stern <stern () rowland ! harvard ! edu>
Date:       2009-11-27 17:18:54
Message-ID: Pine.LNX.4.44L0.0911271215280.30903-100000 () netrider ! rowland ! org
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On Thu, 26 Nov 2009, Marian wrote:

> Alan Stern <stern@...> writes:
> 
> > 
> > On Thu, 26 Nov 2009, Marian wrote:
> > 
> > > Hi all!
> > > 
> > > I have to attach the MEGAWIN USB Bridge (vid=0x0e6a, pid=0x0101) to my Linux 
> > > kernel. I followed the instructions in the kernel documentation and don ´t 
> know 
> > > if either the driver finally doesn ´t fit for the device or I have forgotten 
> to 
> > > configure something.
> > 
> > What is this device?  What is it supposed to do?
> > 
> 
> This device is a cable that connects the Beurer heart rate watch "PM80" (which 
> has 3 serial Pins: RX, TX, GND) with any PC via USB. So within the cable there 
> is a build-in MEGAWIN MA100 controller that maps the USB data to UART and vice 
> versa.
> 
> > 
> > This error message indicates that the device cannot be used as a serial
> > interface, since it doesn't have any bulk endpoints.  So usbserial
> > isn't the right driver for it.  Also, it runs at low speed (1.5 Mb/s) 
> > and doesn't have any way to send data to the computer -- the listing 
> > below shows that it is output only.
> 
> Bad news, I guess...?

Probably.  Perhaps it indicates the device doesn't need to receive any
data from the computer.  Or only minimal data, that can be wrapped up
in a control transfer on endpoint 0.

> > > root <at> dm800:~# cat /proc/bus/usb/devices
> > 
> > > T:  Bus=02 Lev=01 Prnt=01 Port=01 Cnt=01 Dev#=  3 Spd=1.5 MxCh= 0
> > > D:  Ver= 1.10 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
> > > P:  Vendor=0e6a ProdID=0101 Rev= 5.10
> > > S:  Product=USB Bridge
> > > C:* #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=100mA
> > > I:  If#= 0 Alt= 0 #EPs= 1 Cls=ff(vend.) Sub=ff Prot=ff Driver=(none)
> > > E:  Ad=03(O) Atr=03(Int.) MxPS=   8 Ivl=10ms
> > 
> > This doesn't tell much about what the device is intended for.  It uses 
> > a vendor-specific communications protocol, so Linux might not have any 
> > drivers for it.
> 
> Where is the clue that it uses a vendor-specific protocol? I am not very 
> familiar with the USB-Subsystem yet...

On the I: line, it says "Cls=ff(vend.)".  The "vend." is short for 
"vendor-specific".

> I think I will run windows on a VM and try to snoop the usb data produced by the 
> given Windows driver, like Greg Kroah-Hartman introduces here: 
> http://www.linuxjournal.com/article/7582
> Maybe then I can reverse-engineer the windows driver.

That's a good idea.

Alan Stern

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