On 9 November 2011 02:53, John Santos <span dir="ltr"><<a href="mailto:JOHN@egh.com">JOHN@egh.com</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div class="HOEnZb"><div class="h5">On Tue, 8 Nov 2011 <a href="mailto:exarkun@twistedmatrix.com">exarkun@twistedmatrix.com</a> wrote:<br>
<br>
> On 11:59 am, <a href="mailto:dsturmfels@gmail.com">dsturmfels@gmail.com</a> wrote:<br>
> >Hi,<br>
> >Has anyone had much experience with serial flow control in twisted?<br>
><br>
> I don't. :) It sounds like this may not really have much to do with<br>
> Twisted, though.<br>
> >I've been using a twisted serial port in my gtk+ software for quite a<br>
> >while<br>
> >now, and I can get xonxoff flow control to work, but for some reason,<br>
> >rtscts flow control isn't working (or I may be using it wrong).<br>
> ><br>
> >I'm connecting the software, via a usb-serial cable, to a Datalogic<br>
> >barcode<br>
> >scanner cradle.<br>
> >I've been able to replicate this problem with pyserial as well.<br>
><br>
> As you perhaps already know, Twisted's serial port support is<br>
> implemented in terms of pyserial - and the layer Twisted adds is very<br>
> thin. So the problem you experience with pyserial is probably exactly<br>
> the same as the problem you experience with Twisted, since the latter is<br>
> actually the same code as the former.<br>
> ><br>
> >Without flow control on, I can for example, send a particular serial<br>
> >string<br>
> >to the cradle, and the cradle replies instantly with it's software<br>
> >version<br>
> >(as a string).<br>
> >If I scan a barcode, this also instantly shows up in<br>
> >twisted/pyserial/etc<br>
> >(as a string).<br>
> ><br>
> >With xonxoff flow control on in both the software and cradle, the<br>
> >serial<br>
> >connection works exactly the same as having no flow control on.<br>
> ><br>
> >With rtscts flow control on in both the software and cradle however,<br>
> >the<br>
> >cradle doesn't reply instantly with it's software version when the<br>
> >correct<br>
> >string is sent.<br>
> >However, a scanned barcode shows up instantly in the twisted/pyserial<br>
> >software, and if you've previously requested the cradle software<br>
> >version,<br>
> >the software version string only shows up directly after receiving a<br>
> >barcode string.<br>
> ><br>
> >Am I doing something wrong, or does anyone know what might be going on<br>
> >here?<br>
><br>
> Do you know that the device supports RTS/CTS? Do you know that the USB<br>
> driver for the device supports it? Do you know that the USB driver<br>
> support for it is bug free? :)<br>
<br>
</div></div>You also need to know that the serial cable(s) include the necessary<br>
leads, and that the null modem (or whatever) properly crosses them over.<br>
<br>
An RS-232 break-out box (if they are still available) would be very<br>
helpful here.<br>
<div class="im HOEnZb"><br>
><br>
> Sorry I can't add anything more helpful. I think you want to be looking<br>
> for the problem at a pretty low level, though. Perhaps even at the<br>
> level of measuring voltage on the RTS pin...<br>
><br>
> Jean-Paul<br>
><br>
><br>
<br>
</div><span class="HOEnZb"><font color="#888888">--<br>
John Santos<br>
Evans Griffiths & Hart, Inc.<br>
781-861-0670 ext 539<br>
</font></span><div class="HOEnZb"><div class="h5"><br>
<br>
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<a href="http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python" target="_blank">http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python</a><br></div></div></blockquote><div><br>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.<br>
<br>Darcy. <br></div></div><br>