Serial port /dev/cuau0 setup problems

[Tridac]

Hi,

Am working on a project using serial line comms to remote control a radio receiver. That has an rs232 interface at 4800 bauds. Have written some code to drive it, but neither the cfsetispeed or cfsetospeed are setting the baud rate. Using an old protocol analyser, can see that the code is working, sending, receiving, no errors, with a loopback tx to rx on the interface cable, but at the default 9600 bauds, not 4800. Digging around a bit, the Bxxxx baud rate definitions would normally be in termios.h, but are not, and it's not clear where they are defined. The /dev/cuau0 serial port had a lock file, deleted, thinking that it may have an effect, but the default 9600 baud rate stubbornly remains. Can show the code, if that helps, but not flagging up any errors from the various system calls within the open function.. Any ideas appreciated, with thanks ?.

 

[covacat]

try to set the speed on /dev/cuaa0.init

 

[VladiBG]

check/etc/remote for configuration and aliases on /dev/cuau0 for tip(1) and cu(1)

 

[kpedersen]

If its useful, I find this guide for serial programming really useful.

Does cu -s set the baud correctly? Perhaps the hardware itself is locked. Likewise perhaps test with stty(1)

 

[bakul]

Do what covacat says. From uart(4):

Special Devices
     The uart driver also supports an initial-state and a lock-state control
     device for each of the callin and the callout "data" devices.  The
     termios settings of a data device are copied from those of the
     corresponding initial-state device on first opens and are not inherited
     from previous opens.  Use stty(1) in the normal way on the initial-state
     devices to program initial termios states suitable for your setup.
...
FILES
     /dev/ttyu?       for callin ports
     /dev/ttyu?.init
     /dev/ttyu?.lock  corresponding callin initial-state and lock-state
                      devices

     /dev/cuau?       for callout ports
     /dev/cuau?.init
     /dev/cuau?.lock  corresponding callout initial-state and lock-state
                      devices

 

[tingo]

Also, in case the OP is using a usb serial adapter instead of the built in serial port, the device files have an 'U' instead of 'u' before the number.
Like so

root@kg-core2:~ # ll /dev/*U?
crw-rw----  1 uucp dialer 0x22e Oct  5 20:14 /dev/cuaU0
crw-------  1 root wheel  0x22b Oct  4 19:20 /dev/ttyU0

 

[Tridac]

Thanks, tried minicom, terminal emulator, and that could set the baud rate to other than 9600, and checked out ok. Then, played with stty, which reports 9600. Ran minicom again after that, and it now thinks it has a baud rate of zero. Will accept baud rate changes, but still reports zero on the status line. Code fails to work now as well, probably also has the zero baud rate for some reason.

Not using usb serial adapter, real serial port at /dev/cuau0, which normally works fine with minicom.

Seems to be conflicting setups, perhaps a config file somewhere that i'm not aware of ?.

Chris

 

[Tridac]

Just tried this:

stty -f /dev/cuau0 speed 9600
stty -f /dev/cuau0.init speed 9600

Minicom still reports 0 baud rate, so it looks like the serial port is not being setup at all, though minicom would setup and verify 4800 earlier. Work with minicom is normally at 9600, perhaps the default, so that did work ok.

Machine is a dl380 G8, but perhaps I need to try a different platform, with different serial port hardware, as this is not working ?.

Chris

 

[covacat]

you can use stty speed < /dev/cuau0 to show the current speed

 

[Tridac]

Thanks, that reports 9600, but isn't. Don't want to reboot the system, but is there a process for the serial prt, that can be restarted to reinit ?.

 

[covacat]

no default running process. does null modem still work ?
whats the output of stty -a -f /dev/cuau0

 

[Phishfry]

Just wanted to drop a few ideas here:

https://man.freebsd.org/cgi/man.cgi?getty(8)

Good Information in header.

libserialport/freebsd.c at master · sigrokproject/libserialport

Read-only mirror of the official repo at git://sigrok.org/libserialport. Pull requests welcome. Please file bugreports at sigrok.org/bugzilla. - sigrokproject/libserialport

github.com

 

[Tridac]

covecat

Here's the output from stty -a -f /dev/cuau0

speed 9600 baud; 0 rows; 0 columns;
lflags: -icanon -isig -iexten -echo echoe -echok echoke -echonl echoctl
-echoprt -altwerase -noflsh -tostop -flusho -pendin -nokerninfo
-extproc
iflags: -istrip -icrnl -inlcr -igncr -ixon -ixoff ixany imaxbel -ignbrk
-brkint -inpck -ignpar -parmrk iutf8
oflags: -opost onlcr -ocrnl tab0 -onocr -onlret
cflags: cread cs5 parenb parodd hupcl clocal cstopb crtscts dsrflow
dtrflow mdmbuf -rtsdtr
cchars: discard = ^O; dsusp = ^Y; eof = ^D; eol = <undef>;
eol2 = <undef>; erase = ^?; erase2 = ^H; intr = ^C; kill = ^U;
lnext = ^V; min = 0; quit = ^\; reprint = ^R; start = ^Q;
status = ^T; stop = ^S; susp = ^Z; time = 0; werase = ^W;

Also on a laptop with freebsd 15, what looks like the same message content, but minicom shows a baud rate of 9600, which is correct, as far as I can see. Somethng broken in one of the layers. Wonder if there are any systemctl parameters that affect that.

Phishfry

Thanks, Will give that a read through.

 

[covacat]

this looks set to hardware flow control
my cflags look like this (a not connected port on a dl380 g7)
cflags: cread cs8 -parenb -parodd hupcl clocal -cstopb -crtscts -dsrflow
-dtrflow -mdmbuf
"modern" serial adapters like the usb ones have no flowcontrol only rx / tx and ground.
anyway cs5 is unusual

 

[Tridac]

cs5 does look odd, 5 bits ?. So where does the system pick up and set the cuau0 default parameters on boot ?. Has to be a file somewhere that defines that.

 

[covacat]

try this
it's the output of stty -ag on my box

stty gfmt1:cflag=cb00:iflag=2b02:lflag=5cb:oflag=3:discard=f:dsusp=19:eof=4:eol=ff:eol2=ff:erase=7f:erase2=8:intr=3:kill=15:lnext=16:min=1:quit=1c:reprint=12:start=11:status=14:stop=13:susp=1a:time=0:werase=17:ispeed=4800:ospeed=4800 < /dev/cuau0.init