GPIODCF(4) OpenBSD Programmer's Manual GPIODCF(4)NAMEgpiodcf - DCF77/HBG timedelta sensor through GPIO pin
SYNOPSIS
gpiodcf* at gpio? offset 0 mask 0x1
gpiodcf* at gpio?
DESCRIPTION
The gpiodcf driver decodes the DCF77 or HBG time signal code using one
GPIO pin. The pin is used as a data signal. The GPIO pin must be able
to read an input.
The pin number can be specified in the kernel configuration with the
offset locator. The mask locator should always be 0x1 in this case. The
offset and mask can also be specified when gpiodcf is attached at runtime
using the GPIOATTACH ioctl(2) on the gpio(4) device.
gpiodcf implements a timedelta sensor and the delta (in nanoseconds)
between the received time information and the local time can be accessed
through the sysctl(8) interface. The clock type is indicated in the
sensor description:
DCF77 German DCF77 time signal station (77.5 kHz longwave
transmitter located in Mainflingen near Frankfurt).
HBG Swiss HBG time signal station (75 kHz longwave
transmitter located in Prangins near Geneva).
Unknown The clock type has not been determined.
The quality of the timedelta is reported as the sensor status:
UNKNOWN No valid time information has been received yet.
OK The time information is valid and the timedelta is safe
to use for applications like ntpd(8).
WARN The time information is still valid, but no new time
information has been decoded for at least 5 minutes due
to a reception or parity error. The timedelta should
be used with care.
CRITICAL No valid time information has been received for more
than 15 minutes since the sensor state degraded from OK
to WARN. This is an indication that hardware should be
checked to see if it is still functional. The
timedelta will eventually degrade to a lie as all
computer internal clocks have a drift.
SEE ALSOgpio(4), intro(4), ntpd(8), sysctl(8)HISTORY
The gpiodcf driver first appeared in OpenBSD 4.5.
AUTHORS
The gpiodcf driver was written by Marc Balmer <mbalmer@openbsd.org>.
OpenBSD 4.9 November 29, 2008 OpenBSD 4.9
