usb serial programming

[greg@kroah.com (Greg KH)]

On Mon, Jul 21, 2014 at 07:25:24PM +0000, Amadeus W.M. wrote:
> > 
> > What is the:
> > 	Bus 004 Device 008: ID 0764:0501 Cyber Power System, Inc. CP1500 AVR UPS
> > 
> > device?
> 
> That's my backup power supply. 
> 
> 
> > 
> >> Should /dev/ttyUSB0 pop up when I plug the adapter into the usb port,
> >> even before I connect anything to the serial port of the cable? 
> > 
> > Yes.
> > 
> > What happens in the kernel log when you plug the device into the system?
> > 
> > Try doing:
> > 	dmesg -c
> > 	# plug in the adapter now
> > 	dmesg
> > to just see the log messages for that, and not the whole kernel boot
> > log.
> > 
> 2) root:~> dmesg -c   #plug-in adapter
> 3) root:~> dmesg 
> 
> Absolutely nothing. I also did
> 
> tail -f /var/log/messages

Then USB isn't working :(

Or the device isn't, can you plug it into some other computer to test it
out?

> then plugged in the adapter, and again, everything seems dead. The USB port
> is ok, because other devices (e.g. the Fushicai video grabber) do work.

Sounds like a broken device.

> >> If the adapter is not supported, can I write a driver for it? I'll be happy to,
> >> with a little guidance to get me started. Any pointers?
> > 
> > Odds are the device id just needs to be added to an existing driver as
> > I do not know of any "new" usb-serial converter chips that Linux does
> > not already support.
> > 
> 
> Oh, one more thing. Reading about these converters, I saw many use an 
> ftdi chip, so I did modprobed ftdi_elan and ftdi_sio:
> 
> 7) root:~> lsmod | grep ftdi
> ftdi_elan              36689  0 
> ftdi_sio               48770  0 
> 
> In fact, the dmesg above was with the ftdi modules loaded.

You should get some kernel log messages when a new USB device is plugged
in, no matter what type it is.  The fact that you are not is a problem.

greg k-h