On 9 November 2011 02:53, John Santos <j...@egh.com> wrote: > On Tue, 8 Nov 2011 exar...@twistedmatrix.com wrote: > > > On 11:59 am, dsturmf...@gmail.com wrote: > > >Hi, > > >Has anyone had much experience with serial flow control in twisted? > > > > I don't. :) It sounds like this may not really have much to do with > > Twisted, though. > > >I've been using a twisted serial port in my gtk+ software for quite a > > >while > > >now, and I can get xonxoff flow control to work, but for some reason, > > >rtscts flow control isn't working (or I may be using it wrong). > > > > > >I'm connecting the software, via a usb-serial cable, to a Datalogic > > >barcode > > >scanner cradle. > > >I've been able to replicate this problem with pyserial as well. > > > > As you perhaps already know, Twisted's serial port support is > > implemented in terms of pyserial - and the layer Twisted adds is very > > thin. So the problem you experience with pyserial is probably exactly > > the same as the problem you experience with Twisted, since the latter is > > actually the same code as the former. > > > > > >Without flow control on, I can for example, send a particular serial > > >string > > >to the cradle, and the cradle replies instantly with it's software > > >version > > >(as a string). > > >If I scan a barcode, this also instantly shows up in > > >twisted/pyserial/etc > > >(as a string). > > > > > >With xonxoff flow control on in both the software and cradle, the > > >serial > > >connection works exactly the same as having no flow control on. > > > > > >With rtscts flow control on in both the software and cradle however, > > >the > > >cradle doesn't reply instantly with it's software version when the > > >correct > > >string is sent. > > >However, a scanned barcode shows up instantly in the twisted/pyserial > > >software, and if you've previously requested the cradle software > > >version, > > >the software version string only shows up directly after receiving a > > >barcode string. > > > > > >Am I doing something wrong, or does anyone know what might be going on > > >here? > > > > Do you know that the device supports RTS/CTS? Do you know that the USB > > driver for the device supports it? Do you know that the USB driver > > support for it is bug free? :) > > You also need to know that the serial cable(s) include the necessary > leads, and that the null modem (or whatever) properly crosses them over. > > An RS-232 break-out box (if they are still available) would be very > helpful here. > > > > > Sorry I can't add anything more helpful. I think you want to be looking > > for the problem at a pretty low level, though. Perhaps even at the > > level of measuring voltage on the RTS pin... > > > > Jean-Paul > > > > > > -- > John Santos > Evans Griffiths & Hart, Inc. > 781-861-0670 ext 539 > > > _______________________________________________ > Twisted-Python mailing list > Twisted-Python@twistedmatrix.com > http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python >
Thanks John - I'll keep the RS-232 breakout box in mind, if I decide to try rts/cts flow control again in the future. Darcy.
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