Hi Dave and list,
thanks for your answer.
no, my hardware was not changed. I use this Laptop (dell inspiron 1501)
since 2007 together with this adapter.
This adapter is an Ftdi.
The problem occured when updating my debian system a week ago. I can't
exaclty say when.
The only thing i can think of, is my setting for cups, i setted it up to
use my usb Printer, but this cannon Mp150 is also an elder device here.
Better i did dpkg-reconfigure cups; and selected usb, ? ... but i dont
beliefe that this caused anything bad.
thank you for reading, If ever i can help with informations, testing - i
'll do.
kind regards
Lutz
ps: debian unstable
brltty version 4.3dev revision 5246
usb Keyboard , external Harddisc, cannon printer, mouse
and off course ftdi usb2serial adapter
Am 06.08.2010 16:23, schrieb Dave Mielke:
[quoted lines by lutz kaiser on 2010/08/06 at 11:08 +0200]
i found a better way:
some seconds after starting brltty
echo \002\033b>/dev/ttyUSB0
I now understand what's going on. It's a problem we're actually familiar with
whenever a device is connected via USB. Since the CombiBraille uses serial I/O,
I didn't recognize what was going on until I realized that you're using a USB
to serial adapter.
As part of USB communications, there's what amounts to a flag which is commonly
called the endpoint data toggle. It has to be in the same state on both the
host and the device else data isn't transferred. For reasons that I don't
understand, whenever we open a USB device on Linux there's a seemingly high
probability (perhaps 50%) that the data toggle is out of sync. All of our
drivers which support direct USB I/O silently hide this problem by trying up to
three times to get a response from the device. I guess there's also a risk of
this problem occurring for serial devices if a USB to serial adapter is being
used.
Am I correct in understanding that this problem didn't used to happen to you?
Can you remember what change in your system or way of doing things caused it to
start happening? Is it, perhaps, that you used to use a direct serial
connection, and that the problem started occurring when you started to use the
adapter?
--
viele Grüße
Lutz
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