diff options
| -rw-r--r-- | share/man/man4/nmea.4 | 41 |
1 files changed, 37 insertions, 4 deletions
diff --git a/share/man/man4/nmea.4 b/share/man/man4/nmea.4 index 048f8edd50e..761fc5045ea 100644 --- a/share/man/man4/nmea.4 +++ b/share/man/man4/nmea.4 @@ -1,4 +1,4 @@ -.\" $OpenBSD: nmea.4,v 1.6 2006/06/12 09:27:13 mbalmer Exp $ +.\" $OpenBSD: nmea.4,v 1.7 2006/06/14 08:03:08 mbalmer Exp $ .\" .\" Copyright (c) 2006 Marc Balmer <mbalmer@openbsd.org> .\" @@ -23,7 +23,8 @@ .Sh SYNOPSIS .Cd "pseudo-device nmea" Op Ar count .Sh DESCRIPTION -This line discipline interfaces NMEA devices. +This line discipline interfaces NMEA devices, +such as GPS receivers attached to a serial or USB port. .Pp The line discipline is enabled by the following sequence: .Bd -literal -offset indent @@ -34,12 +35,44 @@ ioctl(fildes, TIOCSETD, &ldisc); .Pp The byte stream is unaltered by the line discipline which maintains a timedelta sensor using the NMEA data. +The timedelta sensor will appear as nmea* in the list of sensors and the delta +(in nanoseconds) between the received time information and the local time can +be accessed through the +.Xr sysctl 8 +interface. +.Sh NMEA SENTENCES +The +.Nm +line discipline decodes the following NMEA 0183 sentences: +.Bl -tag -width "GPRMCXX" +.It GPRMC +Recommended minimal navigation information C. +Only the time and date information is extracted. +The warning indication is used to provide the sensor status (see below). +If the attached device sends the GPRMC message in the 13-field format, +the operation mode of the GPS device is reported in the sensor description. +The sensor timestamp is taken when the initial '$' character is received +from the NMEA device. +.El +.Sh SENSOR STATES +The quality of the timedelta is reported as the sensor status: +.Bl -tag -width "WARNXX" +.It OK +The time information is valid. +The timedelta is safe to use for applications like +.Xr ntpd 8 . +.It WARN +The attached GPS receiver indicates a warning condition. +The timedelta should be used with care. +.El .Sh SEE ALSO -.Xr tty 4 +.Xr tty 4 , +.Xr ntpd 8 , +.Xr sysctl 8 .Sh HISTORY The .Nm -interface appeared in +interface first appeared in .Ox 4.0 . .Sh AUTHORS The |