= Generic Reference Driver
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== Name

refclock_generic - multidevice parse driver for generic time radios and GPSDOs.

== Synopsis

["verse",subs="normal"]
Name: generic
Reference ID: DCF | DCFa | DCFp | GPS | MSF
Serial Port: /dev/refclock-'u'; TTY mode according to clock type
PPS device: /dev/refclockpps-'u'; alternate PPS device

== Warning

Most modes of this driver report only two-digit years, and are thus
reliant on the system clock to be near correct before samples will be
processed properly. You will not be able to use these modes to run
autonomously, nor will they reliably recover from a trashed or zeroed
system clock.  The only exceptions are the Schweitzer 240x and the
Trimble TAIP/TSIP modes.

== Description

The generic driver supports many different clock
types/configurations by plugging type-specific packet-parsing
routines into a generic driver framework.

Note that some of these subtypes below are to support equipment that
has not been commercially available for a long time, report only
2-digit years (thus being subject to lingering Y2K problems and
possible future issues near century boundaries), and may be removed in
a future release.  See
https://www.ntpsec.org/removal-plan.html[Feature removals] for a
discussion of this issue.

The actual receiver status is mapped into various synchronization states
generally used by receivers. The driver is configured to interpret the
time codes of Meinberg DCF77 AM receivers, DCF77 FM receivers, Meinberg
GPS16x/17x receivers, Trimble SV6 GPS, ELV DCF7000, Schmid, Wharton 400A
and various low-cost receivers.

The reference clock support in NTP contains the necessary configuration
tables for those receivers. In addition to supporting several different
clock types and multiple devices, the processing of a PPS signal is also
provided as a configuration option. The PPS configuration option uses
the receiver-generated time stamps for feeding the PPS loopfilter
control for much finer clock synchronization.

CAUTION: The PPS configuration option is different from the hardware PPS
signal, which is also supported (see below), as it controls the way ntpd
is synchronized to the reference clock, while the hardware PPS signal
controls the way time offsets are determined.

The use of the PPS option requires receivers with an accuracy of better
than 1ms.

== Timecode variables listed by {ntpqman}

The ntpq program can read and display several clock variables. These
hold the following information:

refclock_format::
  A qualification of the decoded time code format.
refclock_states::
  The overall running time and the accumulated times for the clock event
  states.
refclock_status::
  Lists the currently active receiver flags. Additional feature flags
  for the receiver are optionally listed in parentheses.
refclock_time::
  The local time with the offset to UTC (format HHMM).
timecode::
  The actual time code.

If PPS information is present, additional variables are available:

refclock_ppsskew::
  The difference between the RS-232-derived timestamp and the PPS
  timestamp.
refclock_ppstime::
  The PPS timestamp.

== Supported Devices

Twenty-five clock types are supported by the GENERIC driver
and any number of these clocks may be operational at any one time.

Note: Under NTPsec, you _must_ use the new configuration syntax
(refclock generic subtype N) to declare generic clocks, rather than
the old-style syntax with a magic address, unless the software has
been built with the +--enable-classic-mode+ option in which case *only*
the old-style syntax will work.

A note on the implementations:

* These implementations were mainly done without actual access to the
hardware, thus not all implementations provide full support. The
development was done with the help of many kind souls who had the
hardware and kindly lent me their time and patience during the
development and debugging cycle. Thus for continued support and quality,
direct access to the receivers is a big help. Nevertheless I am not
prepared to buy these reference clocks - donations to
(mailto:kardel@ntp.org[kardel@ntp.org]) are welcome as
long as they work within Europe 8-).
+
The pictures below have been archived from the vendors' web pages.
+
Verified implementations are:

* *RAWDCF variants*
+
These variants have been tested for correct decoding with my own
homegrown receivers. Interfacing with specific commercial products may
involve some fiddling with cables. In particular, commercial RAWDCF
receivers have a seemingly unlimited number of ways to draw power from
the RS-232 port and to encode the DCF77 datastream. You are mainly on
your own here unless I have a sample of the receiver.

* * https://www.meinberg.de[Meinberg clocks] *
+
These implementations have been verified by the Meinberg people
themselves and I have access to one of these clocks.


* https://selinc.com[Schweitzer Engineering Laboratories SEL-240x clocks] *
+
This implementation was provided and verified by SEL and
https://www.nwtime.org/[Network Time Foundation] has an
SEL-2407 in one of its development labs.

* *refclock generic subtype 0*
+
*https://www.meinberg.de[Meinberg] https://www.meinbergglobal.com/english/archive/pzf511.htm[PZF5xx receiver family] (FM demodulation/TCXO / 50&mu;s)*
+
WARNING: This equipment is no longer available for commercial sale, and
support may be removed in the future.  See:
https://www.ntpsec.org/removal-plan.html[Feature removals]

* *refclock generic subtype 1*
+
*https://www.meinberg.de[Meinberg] https://www.meinbergglobal.com/english/archive/pzf511.htm[PZF5xx receiver family] (FM demodulation/OCXO / 50&mu;s)*
+
WARNING: This equipment is no longer available for commercial sale, and
support may be removed in the future.  See:
https://www.ntpsec.org/removal-plan.html[Feature removals]

image::pic/pzf511.jpg[https://www.meinberg.de/english/products/pzf-eurocard.htm]

* *refclock generic subtype 2*
+
*https://www.meinberg.de[Meinberg] https://www.meinbergglobal.com/english/archive/c51.htm[DCF C51 receiver and similar] (AM demodulation / 4ms)*
+
image:pic/c51.jpg[https://www.meinberg.de/english/products/c51.htm]
+
This subtype expects the Meinberg standard time string format with 9600/7E2.
+
*Note:* subtype 2 must also be used for
https://www.meinberg.de/english/products/formfactor.htm#slot_card[Meinberg
PCI cards] under Linux, e.g.
https://www.meinberg.de/english/products/gps-pcicard.htm[the GPS PCI
card] or https://www.meinberg.de/english/products/dcf-pcicard.htm[the
DCF77 PCI card]. Please note the
https://www.meinberg.de/english/sw/#linux[Meinberg Linux driver] must be
installed. That driver emulates a refclock device in order to allow ntpd
to access those cards. For details, please refer to the README file
that comes with the Meinberg driver package.

* *refclock generic subtype 3*
+
https://www.elv.de/[ELV] *DCF7000 (sloppy AM demodulation / 50ms)*
+
WARNING: This equipment is no longer available for commercial sale, and
support may be removed in the future.  See:
https://www.ntpsec.org/removal-plan.html[Feature removals]

* *refclock generic subtype 4*
+
*Walter Schmid DCF receiver Kit (AM demodulation / 1ms)*
+
WARNING: This equipment is no longer available for commercial sale, and
support may be removed in the future.  See:
https://www.ntpsec.org/removal-plan.html[Feature removals]

* *refclock generic subtype 5*
+
*RAW DCF77 100/200ms pulses (Conrad DCF77 receiver module / 5ms)*

* *refclock generic subtype 6*
+
*RAW DCF77 100/200ms pulses (TimeBrick DCF77 receiver module / 5ms)*

* *refclock generic subtype 7*
+
* https://www.meinberg.de[Meinberg] https://www.meinberg.de/english/products/timesource.htm#gps---freq_sync[GPS16x/GPS17x receivers] (GPS / <<1&mu;s) *
+
image:pic/gps167.jpg[https://www.meinberg.de/english/products/gps-eurocard.htm]
+
This subtype expects either the University of Erlangen time string format
or the Meinberg standard time string format at 19200/8N1.
+
The University of Erlangen format is preferred. Newer Meinberg GPS
receivers can be configured to transmit that format; for older devices,
a special firmware version may be available.
+
In this subtype some additional GPS receiver status information is also
read. However, this requires a point-to-point connection.
xref:subtype18[Subtype 18] should be used if the device is accessed by a multidrop connection.
+
*Note:* subtype 7 must not be used with Meinberg PCI cards; use subtype 2 instead.

* *refclock generic subtype 8*
+
https://www.igel.de/[IGEL] https://www.igel.de/eigelmn.html[clock]
+
image:pic/igclock.gif[https://www.igel.de/eigelmn.html]

* *refclock generic subtype 9*
+
*https://www.trimble.com[Trimble] ftp://ftp.trimble.com/pub/sct/embedded/bin/Data%20Sheets/SveeSix2.PDF[SVeeSix GPS receiver] TAIP protocol (GPS / <<1&mu;s)*
+
WARNING: This equipment is no longer available for commercial sale, and
support may be removed in the future.  See:
https://www.ntpsec.org/removal-plan.html[Feature removals]

* *refclock generic subtype 10*
+
*https://www.trimble.com[Trimble] ftp://ftp.trimble.com/pub/sct/embedded/bin/Data%20Sheets/SveeSix2.PDF[SVeeSix GPS receiver] TSIP protocol (GPS / <<1&mu;s) (no kernel support yet)*
+
WARNING: This equipment is no longer available for commercial sale, and
support may be removed in the future.  See:
https://www.ntpsec.org/removal-plan.html[Feature removals]
+
image:pic/pd_om011.gif[https://www.trimble.com/cgi/omprod.cgi/pd_om011.html]
+
image:pic/pd_om006.gif[https://www.trimble.com/cgi/omprod.cgi/pd_om006.html]

* *refclock generic subtype 11*
+
*Radiocode Clocks Ltd RCC 8000 Intelligent Off-Air Master Clock support*

* *refclock generic subtype 12*
+
*https://www.hopf-time.com[HOPF] https://www.hopf.com/downloads/manuals/6021gps_v0601_en.pdf[Funkuhr 6021]*
+
image:pic/fg6021.gif[https://www.hopf-time.com/engl/kart6021.html]

* *refclock generic subtype 13*
+
*Diem's Computime Radio Clock*

* *refclock generic subtype 14*
+
*RAWDCF receiver (DTR=high/RTS=low)*

* *refclock generic subtype 15*
+
*WHARTON 400A Series Clocks with a 404.2 Serial Interface*

* *refclock generic subtype 16*
+
*RAWDCF receiver (DTR=low/RTS=high)*

* *refclock generic subtype 17*
+
*VARITEXT Receiver (MSF)*

* [[subtype18]]*refclock generic subtype 18*
+
*https://www.meinberg.de[Meinberg] https://www.meinberg.de/english/products/timesource.htm#gps---freq_sync[GPS16x/GPS17x receivers] (GPS / <<1&mu;s)*
+
This subtype works without additional data communication (version, GPS
status etc.) and thus should be used with multidrop, heterogeneous
multiclient operation.
+
*Note:* subtype 18 must not be used with Meinberg PCI cards, use subtype 2
instead.

* *refclock generic subtype 19*
+
*Gude Analog- und Digitalsystem GmbH \'Expert mouseCLOCK USB v2.0'*

* *refclock generic subtype 20*
+
*RAWDCF receiver similar to subtype 14, but operating @ 75 baud (DTR=high/RTS=low)*
+
Driving the DCF clocks at 75 baud may help to get them to work with a
bunch of common USB serial converters, that do 75 but cannot do 50 baud
at all, e.g. those based on Prolific PL2303.

* *refclock generic subtype 21*
+
*RAWDCF receiver similar to subtype 16, but operating @ 75 baud (DTR=low/RTS=high)*
+
See comment from subtype 20 clock.

* *refclock generic subtype 22*
+
*MEINBERG, subtype 2 but with POWERUP trust*

* *refclock generic subtype 23*
+
*MEINBERG, subtype 7 but with POWERUP trust*

* *refclock generic subtype 24*
+
*https://selinc.com/[Schweitzer Engineering Laboratories]*

Actual data formats and setup requirements of the various clocks can be
found in link:parsedata.html[NTP GENERIC clock data formats].

== Operation

The reference clock support software carefully monitors the state
transitions of the receiver. All state changes and exceptional events
(such as loss of time code transmission) are logged via the syslog
facility. Every hour a summary of the accumulated times for the clock
states is listed via syslog.

PPS support is only available when the receiver is completely
synchronized. The receiver is believed to deliver correct time for an
additional period of time after losing synchronization, unless a
disruption in time code transmission is detected (possible power loss).
The trust period is dependent on the receiver oscillator and thus is a
function of clock type.

Raw DCF77 pulses can be fed via a level converter to the RXD pin of an
RS-232 serial port (pin 3 of a 25-pin connector or pin 2 of a 9-pin
connector). The telegrams are decoded and used for synchronization.
DCF77 AM receivers can be bought for as little as $25. The accuracy is
dependent on the receiver and is somewhere between 2 ms (expensive) and
10 ms (cheap). Synchronization ceases when reception of the DCF77 signal
deteriorates, since no backup oscillator is available as usually found
in other reference clock receivers. So it is important to have a good
place for the DCF77 antenna. During transmitter shutdowns you are out of
luck unless you have other NTP servers with alternate time sources
available.

In addition to the PPS loopfilter control, a true PPS hardware signal
can be utilized via the PPSAPI interface. PPS pulses are usually fed via
a level converter to the DCD pin of an RS-232 serial port (pin 8 of a
25-pin connector or pin 1 of a 9-pin connector), where one edge of the pulse
-- often the leading edge, but in many cases not -- provides the reference.
NTPsec uses the edge of the pulse specified by the driver for the particular
hardware used. To select PPS support, the subtype parameter is the subtype
value as above plus 128. If 128 is not added to the subtype value, PPS will
be detected to be available but will not be used.

== Hardware PPS support

For PPS to be used, add 128 to the subtype parameter.

If the PPS signal is fed in from a device different from the device
providing the serial communication (/dev/refclock-\{0..3}), this device
is configured as /dev/refclockpps-\{0..3}. This allows the PPS
information to be fed in e.g. via the parallel port (if supported by the
underlying operation system) and the date/time telegrams to be handled
via the serial port.

== Monitor Data

Clock state statistics are written hourly to the syslog
service. Online information can be found by examining the clock
variables via the ntpq cv command.

Some devices have quite extensive additional information
(GPS16x/GPS17x, Trimble). The driver reads out much of the internal GPS
data and makes it accessible via clock variables. To find out about
additional variable names, query for the clock_var_list variable on a
specific clock association as shown below.

First let ntpq display the table of associations:

-------------------------------------------------------------
  ntpq> as
  ind assID status  conf reach auth  condition last_event cnt
  ===========================================================
  1   19556  9154   yes   yes  none  falsetick  reachable  5
  2   19557  9435   yes   yes  none  candidate clock expt  3
  3   19558  9714   yes   yes  none   pps.peer  reachable  1
-------------------------------------------------------------


Then switch to raw output. This may be required because of display
limitations in ntpq/ntpd - so large lists need to be retrieved in
several queries.

----------------------------------------
  ntpq> raw
  Output set to raw
----------------------------------------

Use the cv command to read the list of clock variables of a selected
association:

----------------------------------------
  ntpq> cv 19557 clock_var_list
----------------------------------------

The long output of the command above looks similar to:

----------------------------------------
  assID=19557 status=0x0000,
  clock_var_list="type,timecode,poll,noreply,badformat,baddata,fudgetime1,
  fudgetime2,stratum,refid,flags,device,clock_var_list,refclock_time,refclock_status,
  refclock_format,refclock_states,refclock_id,refclock_iomode,refclock_driver_version,
  meinberg_gps_status,gps_utc_correction,gps_message,meinberg_antenna_status,gps_tot_51,
  gps_tot_63,gps_t0a,gps_cfg[1],gps_health[1],gps_cfg[2],gps_health[2],gps_cfg[3],
  gps_health[3],gps_cfg[4],gps_health[4],gps_cfg[5]"
----------------------------------------

Then use the cv command again to list selected clock variables. The
following command must be entered as a single line:

----------------------------------------
  ntpq> cv 19557 refclock_status,refclock_format,refclock_states,refclock_id,    refclock_iomode,refclock_driver_version,meinberg_gps_status,gps_utc_correction,    gps_message,meinberg_antenna_status,gps_tot_51,gps_tot_63,gps_t0a,gps_cfg[1],    gps_health[1],gps_cfg[2],gps_health[2],gps_cfg[3],gps_health[3],gps_cfg[4],    gps_health[4],gps_cfg[5]
----------------------------------------

The output of the command above is wrapped around depending on the
screen width and looks similar to:

----------------------------------------
  status=0x0003,
  refclock_status="UTC DISPLAY; TIME CODE; PPS; POSITION; (LEAP INDICATION;    PPS SIGNAL; POSITION)",
  refclock_format="Meinberg GPS Extended",
  refclock_states="*NOMINAL: 21:21:36 (99.99%); FAULT: 00:00:03 (0.00%);  running time: 21:21:39",
  refclock_id="GPS", refclock_iomode="normal",
  refclock_driver_version="refclock_parse.c,v 4.77 2006/08/05 07:44:49
  kardel RELEASE_20060805_A",
  meinberg_gps_status="[0x0000] <OK>",
  gps_utc_correction="current correction 14 sec, last correction on c7619a00.00000000  Sun, Jan  1 2006  0:00:00.000",
  gps_message="/PFU3SOP-4WG14EPU0V1KA",
  meinberg_antenna_status="RECONNECTED on 2006-07-18 08:13:20.0000000
  (+0000)    UTC CORR, LOCAL TIME, reconnect clockoffset +0.0000000 s,
  disconnect time 0000-00-00 00:00:00.0000000 (+0000) ",
  gps_tot_51="week 1400 + 3 days + 42300.0000000 sec",
  gps_tot_63="week 1400 + 3 days + 42294.0000000 sec",
  gps_t0a="week 1400 + 5 days + 71808.0000000 sec",
  gps_cfg[1]="[0x9] BLOCK II", gps_health[1]="[0x0] OK;SIGNAL OK",
  gps_cfg[2]="[0x0] BLOCK I", gps_health[2]="[0x3f] PARITY;MULTIPLE ERRS",
  gps_cfg[3]="[0x9] BLOCK II", gps_health[3]="[0x0] OK;SIGNAL OK",
  gps_cfg[4]="[0x9] BLOCK II", gps_health[6]="[0x0] OK;SIGNAL OK",
  gps_cfg[5]="[0x9] BLOCK II"
----------------------------------------

== Driver Options

+unit+ 'number'::
  The driver unit number, defaulting to 0. Used as a distinguishing
  suffix in the driver device name.
+time1+ _time_ ::
  Specifies the time offset calibration factor, in seconds and fraction.
  The default value depends on the clock type.
+time2+ _time_ ::
  If flag1 is 0, time2 specifies the offset of the PPS signal from the
  actual time (PPS fine tuning).  If flag1 is 1, time2 specifies the
  number of seconds a receiver with a premium local oscillator can be
  trusted after losing synchronisation.
+stratum+ _stratum_ ::
  The stratum for this reference clock.
+refid+ _refid_ ::
  The reference id for this reference clock.

+flag1 {0 | 1}+::
  If 0, the fudge factor time2 refers to the PPS offset. +
  If 1, time2 refers to the TRUST TIME.
+flag2 {0 | 1}+::
  If flag2 is 1, sample PPS on CLEAR instead of on ASSERT.
+flag3 {0 | 1}+::
  If flag3 is 1, link kernel PPS tracking to this refclock instance.
+flag4 {0 | 1}+::
  Delete next leap second instead of adding it. (You'll need to wait a
  bit for that to happen 8-)
+subtype+::
  Used to select the device type and serial parameters.
+mode+::
  Synonym for subtype, retained for backward compatibility.
+path+ 'filename'::
  Overrides the default device path.
+ppspath+ 'filename'::
  Overrides the default PPS-device path.
+baud+ 'number'::
  Not used by this driver.  Baud rate is implied by the selected mode.

== Configuration Examples

See the examples above under "Supported devices"

== Making your own generic clocks

The generic clock mechanism deviates from the way other NTP reference
clocks work. For a short description of how to build generic reference
clocks, see link:generic_howto.html[making generic clocks].

Additional Information

link:refclock.html[Reference Clock Drivers]

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