Flow control setting

[GoogleCodeExporter]

I am facing intermittent port hangs which can be resolved by unplugging the USB 
cable and in some stubborn situations by rebooting the computer. My 
configuration is specified at the bottom of this post.

Based on some investigation, I want to get some input on whether the following 
could be an issue. My modem documentation says it is set to flow control 'none' 
by default. AT+IFC? returns "+IFC: 0,0". I see that smslib sets 
FLOWCONTROL_RTSCTS_IN on the serial port. Does smslib assume that all modems 
will have hardware flow control set? Does my current setup violate that 
assumption? Would this lead to bad stuff happening, like the port hangs?

System Configuration
smslib 3.4.6
JavaComm library
Siemens TC35i Modem
Virtual COM ports based on FTDI USB-Serial converter
Windows 7, 32 bit

Original issue reported on code.google.com by nizam.mo...@gmail.com on 17 Jul 2011 at 8:24

[GoogleCodeExporter]

Well, you could disable FLOWCONTROL_RTSCTS_IN - but try with low speeds. Start 
with something like 9600 and see how it goes.

Original comment by T.Delenikas on 18 Jul 2011 at 7:37

• Changed state: Feedback

[GoogleCodeExporter]

The problem appears to be with the USB port shutting down due to apparent power 
issues.  This can be detected from the device manager where the respective USB 
root hub will show an "unknown" for the power usage of the malfunctioning 
device. The symptom in smslib for this scenario is that the modem restart will 
indicate "Port currently owned by unknown windows application". Unplugging and 
plugging the USB cable solves the issue. I am still hunting for reliable 
powered USB hubs. Till then my modems are directly plugged into the computers 
USB ports, and things are stable now. Only issue is I'm limited by the number 
of USB ports.

Original comment by nizam.mo...@gmail.com on 19 Oct 2011 at 1:42

[GoogleCodeExporter]

Thank you for the feedback - USB hubs can be a big headache... Hope you find 
one that works.

Original comment by T.Delenikas on 19 Oct 2011 at 7:41

• Changed state: Closed