unable to loopback RTS to CTS
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unable to loopback RTS to CTS
by cdaviduik
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Hello,
I am using a gumstix verdex XL6P with a consoleLCD16 board and via the BTUART (/dev/ttyS1) am attempting to loopback RTS to CTS. So far I have been successful in looping Tx back to Rx but, using the same setup, cannot reproduce the results using RTS and CTS. Although the RTS can be seen (via oscilloscope) to change value, there is no change received in the CTS line. My code for getting/setting the serial lines: -------------------------------------------------- tcgetattr(fd, &options); options.c_cflag &= ~CRTSCTS; options.c_oflag = 0; tcsetattr(fd, TCSANOW, &options); // set RTS high ioctl(fd, TIOCMGET, &controlbits); controlbits |= TIOCM_RTS; ioctl(fd, TIOCMSET, &controlbits); sleep(1); // get CTS ioctl(fd, TIOCMGET, &controlbits); cts_state = controlbits & TIOCM_CTS; printf("CTS: %s\n", cts_state ? "on" : "off"); -------------------------------------------------- From what I understand after setting RTS high then the controlbits received via ioctl(f, TIOCMGET, &controlbits) should indicate CTS is high if RTS is loopback to CTS (i.e. connected together). Unfortunately this is not the case as CTS is always read as "off". Any help would be much appreciated. Thank you. |
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Re: unable to loopback RTS to CTS
by cdaviduik
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When RTS is looped back to CTS and hardware flow control is set to "on", communication is frozen when RTS/CTS goes high. Unfortunately in this state the program reading and setting the serial lines is also frozen and thus unable to read that CTS is high. If hardware flow control is set to "off", then RTS can be toggled high or low however CTS is always read as low.
I am attempting to edit the serial drivers such that CTS will still read high or low even when hardware flow control is turned off and noticed there is a function "uart_handle_cts_change(struct uart_port *port, unsigned int status)" in serial_core.h that appears to handle when CTS changes state. After making some small changes, adding some "printk" messages, I created a patch, edited my bitbake file, rebuilt it, and then put it on the gumstix. Navigating to "/lib/modules/2.6.21/kernel/drivers/serial", I noticed the size of the 8250.ko had increased in size slightly, which I assume is due to my changes, but when I run my program there does not appear to be any change in behavior nor do any of my printk messages appear on the console. I do not mind spending some time determining what changes need to be made to the drivers, however at this point it does not appear that the changes I am making are having any impact at all. Are there perhaps some steps I am missing? Has anyone attempted a similar task? Thank You
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Re: unable to loopback RTS to CTS
by Dave Hylands
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Hi,
> When RTS is looped back to CTS and hardware flow control is set to "on", > communication is frozen when RTS/CTS goes high. Unfortunately in this state > the program reading and setting the serial lines is also frozen and thus > unable to read that CTS is high. If hardware flow control is set to "off", > then RTS can be toggled high or low however CTS is always read as low. Which port are you referring to? Only the BTUART port has a CTS/RTS signal present. On the FFUART, the CTS and RTS pins are hooked up the USB circuitry, and the STUART has no CTS/RTS line. -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ ------------------------------------------------------------------------- Sponsored by: SourceForge.net Community Choice Awards: VOTE NOW! Studies have shown that voting for your favorite open source project, along with a healthy diet, reduces your potential for chronic lameness and boredom. Vote Now at http://www.sourceforge.net/community/cca08 _______________________________________________ gumstix-users mailing list gumstix-users@... https://lists.sourceforge.net/lists/listinfo/gumstix-users |
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Re: unable to loopback RTS to CTS
by Ned Forrester
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cdaviduik wrote:
> Navigating to "/lib/modules/2.6.21/kernel/drivers/serial", I noticed the > size of the 8250.ko had increased in size slightly, which I assume is due to > my changes, but when I run my program there does not appear to be any change > in behavior nor do any of my printk messages appear on the console. I can't directly address your problem, other than to say that I have made changes to the serial driver under buildroot without any problems. If you are not seeing your printks, make sure that you are issuing them at a level that is currently enabled for printing (KERN_ERR, KERN_DEBUG, KERN_INFO, etc.). The current printk level can be changed with echo n > /proc/sys/kernel/printk where 1<n<8. Setting n to 8 enables all messages. The current log level can be read as the first digit reported by: cat /proc/sys/kernel/printk The order of printk levels, from most severe (always printed) to least is: KERN_EMERG KERN_ALERT KERN_CRIT KERN_ERR KERN_WARNING KERN_NOTICE KERN_INFO KERN_DEBUG -- Ned Forrester nforrester@... Oceanographic Systems Lab 508-289-2226 Applied Ocean Physics and Engineering Dept. Woods Hole Oceanographic Institution Woods Hole, MA 02543, USA http://www.whoi.edu/sbl/liteSite.do?litesiteid=7212 http://www.whoi.edu/hpb/Site.do?id=1532 http://www.whoi.edu/page.do?pid=10079 ------------------------------------------------------------------------- Sponsored by: SourceForge.net Community Choice Awards: VOTE NOW! Studies have shown that voting for your favorite open source project, along with a healthy diet, reduces your potential for chronic lameness and boredom. Vote Now at http://www.sourceforge.net/community/cca08 _______________________________________________ gumstix-users mailing list gumstix-users@... https://lists.sourceforge.net/lists/listinfo/gumstix-users |
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Re: unable to loopback RTS to CTS
by cdaviduik
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I am using the BTUART on /dev/ttyS1 and am issuing my printk's with KERN_ALERT. The first digit of "cat /proc/sys/kernel/printk" is 7 so I imagine I should be seeing my messages if the code is in fact reaching them.
Thanks
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Re: unable to loopback RTS to CTS
by Ned Forrester
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cdaviduik wrote:
> I am using the BTUART on /dev/ttyS1 and am issuing my printk's with > KERN_ALERT. The first digit of "cat /proc/sys/kernel/printk" is 7 so I > imagine I should be seeing my messages if the code is in fact reaching them. Sounds right. -- Ned Forrester nforrester@... Oceanographic Systems Lab 508-289-2226 Applied Ocean Physics and Engineering Dept. Woods Hole Oceanographic Institution Woods Hole, MA 02543, USA http://www.whoi.edu/sbl/liteSite.do?litesiteid=7212 http://www.whoi.edu/hpb/Site.do?id=1532 http://www.whoi.edu/page.do?pid=10079 ------------------------------------------------------------------------- Sponsored by: SourceForge.net Community Choice Awards: VOTE NOW! Studies have shown that voting for your favorite open source project, along with a healthy diet, reduces your potential for chronic lameness and boredom. Vote Now at http://www.sourceforge.net/community/cca08 _______________________________________________ gumstix-users mailing list gumstix-users@... https://lists.sourceforge.net/lists/listinfo/gumstix-users |
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Re: unable to loopback RTS to CTS
by cdaviduik
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Is anyone sure exactly which functions are getting called in which files (drivers) when I am communication via the BTUART? Perhaps I just do not have my printk messages where they can be reached.
Any amount of pointing in the right (or nearby) direction would be very helpful. Thanks
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Re: unable to loopback RTS to CTS
by Dave Hylands
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Hi,
> Is anyone sure exactly which functions are getting called in which files > (drivers) when I am communication via the BTUART? Perhaps I just do not have > my printk messages where they can be reached. The low level file, which talks to the hardware, is in drivers/serial/pxa.c The functions: serial_pxa_get_mctrl and serial_pxa_set_mctrl are the ones which query CTS and set RTS. -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ ------------------------------------------------------------------------- Sponsored by: SourceForge.net Community Choice Awards: VOTE NOW! Studies have shown that voting for your favorite open source project, along with a healthy diet, reduces your potential for chronic lameness and boredom. Vote Now at http://www.sourceforge.net/community/cca08 _______________________________________________ gumstix-users mailing list gumstix-users@... https://lists.sourceforge.net/lists/listinfo/gumstix-users |
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Re: unable to loopback RTS to CTS
by Ned Forrester
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cdaviduik wrote:
> Is anyone sure exactly which functions are getting called in which files > (drivers) when I am communication via the BTUART? Perhaps I just do not have > my printk messages where they can be reached. > > Any amount of pointing in the right (or nearby) direction would be very > helpful. The file I edited to change the serial driver was in the kernel tree at: drivers/serial/pxa.c Remember that I am using buildroot with a 2.6.20 kernel, so your setup may be different, but I doubt it. -- Ned Forrester nforrester@... Oceanographic Systems Lab 508-289-2226 Applied Ocean Physics and Engineering Dept. Woods Hole Oceanographic Institution Woods Hole, MA 02543, USA http://www.whoi.edu/sbl/liteSite.do?litesiteid=7212 http://www.whoi.edu/hpb/Site.do?id=1532 http://www.whoi.edu/page.do?pid=10079 ------------------------------------------------------------------------- Sponsored by: SourceForge.net Community Choice Awards: VOTE NOW! Studies have shown that voting for your favorite open source project, along with a healthy diet, reduces your potential for chronic lameness and boredom. Vote Now at http://www.sourceforge.net/community/cca08 _______________________________________________ gumstix-users mailing list gumstix-users@... https://lists.sourceforge.net/lists/listinfo/gumstix-users |
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