serial module

[John Nagle]

On 5/22/2012 2:07 PM, Paul Rubin wrote:
> John Nagle<nagle at animats.com>  writes:
>>     If a device is registered as /dev/ttyUSBnn, one would hope that
>> the Linux USB insertion event handler, which assigns that name,
>> determined that the device was a serial port emulator.  Unfortunately,
>> the USB standard device classes
>> (http://www.usb.org/developers/defined_class) don't have "serial port
>> emulator" as a standardized device.  So there's more variation in this
>> area than in keyboards, mice, or storage devices.
>
> Hmm, I've been using USB-to-serial adapters and so far they've worked
> just fine.  I plug the USB end of adapter into a Ubuntu box, see
> /dev/ttyUSB* appear, plug the serial end into the external serial
> device, and just use pyserial like with an actual serial port.  I didn't
> realize there were issues with this.

    There are.  See "http://wiki.debian.org/usbserial".  Because there's
no standard USB class for such devices, the specific vendor ID/product
ID pair has to be known to the OS.  In Linux, there's a file of these,
but not all USB to serial adapters are in it.  In Windows, there
tends to be a vendor-provided driver for each brand of USB to
serial converter.  This all would have been much simpler if the USB
Consortium had defined a USB class for these devices, as they did
for keyboards, mice, etc.

    However, this is not the original poster's problem.

					John Nagle