Subject: Re: setting up serial port for GPS NTP source
To: Danny Thomas <D.Thomas@imb.uq.edu.au>
From: Roger Brooks <R.S.Brooks@liverpool.ac.uk>
List: netbsd-help
Date: 08/23/2000 12:39:52
On Wed, 23 Aug 2000, Danny Thomas wrote:
>I'm finally trying to hook up my GPS receiver. I've tested it by booting my
>PC from a DOS floppy and using a simple terminal. The serial stream reports
>the GPS consistently receiving 6-9 satellites at adequate strength, and I
>can also use the terminal to reconfigure the Garmin GPS25LVS module.
>
>So at least the antenna, cable, GPS and connector cables are working, but
>before hooking up the PPS signal and using the generic NMEA driver in ntp4,
>I want to make sure the serial port is properly working. This may not be
>strictly necessary since the NMEA driver does it's own serial setup, but
>I'm also considering using a separate perl script to talk to the GPS.
>Unfortunately my cluelessness intrudes.
>
>1) the MSDOS terminal works using COM2 so that meant /dev/tty01 ?
>
>2) I tried changing the speed of the com port without success
> www2# stty -f /dev/tty01 speed 4800
> 9600 <= should it echo this?
> www2# stty -f /dev/tty01
> ispeed 0 baud; ospeed 9600 baud; <= still 9600
> lflags: echoe echoke echoctl
> oflags: onocr onlret
> cflags: cs8 -parenb
> is that the right way? but why isn't the change at least being reported
> or coming into effect? I've tried changing other parameters too.
> NB I've tried this single user, and tried relaxing permissions
> www2# ls -l /dev/tty0*
> crw------- 1 uucp wheel 8, 0 May 20 12:50 /dev/tty00
> crwxrwxrwx 1 uucp wheel 8, 1 May 20 12:50 /dev/tty01
This won't work, because on each open of a tty port the driver resets
everything to default values <sys/ttydefaults.h>. So what you have just
set with stty is discarded when you open the port again with cat. The
usual way to do this is in a subshell with stdin redirected
(stty 4800 ; cat )< /dev/tty01
Roger
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