/* * refclock_arc - clock driver for ARCRON MSF/DCF/WWVB receivers */#ifdef HAVE_CONFIG_H#include <config.h>#endif#if defined(REFCLOCK) && defined(CLOCK_ARCRON_MSF)static const char arc_version[] = { "V1.3 2003/02/21" };/* define PRE_NTP420 for compatibility to previous versions of NTP (at least   to 4.1.0 */#undef PRE_NTP420#ifndef ARCRON_NOT_KEEN#define ARCRON_KEEN 1 /* Be keen, and trusting of the clock, if defined. */#endif#ifndef ARCRON_NOT_MULTIPLE_SAMPLES#define ARCRON_MULTIPLE_SAMPLES 1 /* Use all timestamp bytes as samples. */#endif#ifndef ARCRON_NOT_LEAPSECOND_KEEN#ifndef ARCRON_LEAPSECOND_KEEN#undef ARCRON_LEAPSECOND_KEEN /* Respond quickly to leap seconds: doesn't work yet. */#endif#endif/*Code by Derek Mulcahy, <derek@toybox.demon.co.uk>, 1997.Modifications by Damon Hart-Davis, <d@hd.org>, 1997.Modifications by Paul Alfille, <palfille@partners.org>, 2003.Modifications by Christopher Price, <cprice@cs-home.com>, 2003.Modifications by Nigel Roles <nigel@9fs.org>, 2003.THIS CODE IS SUPPLIED AS IS, WITH NO WARRANTY OF ANY KIND.  USE ATYOUR OWN RISK.Orginally developed and used with ntp3-5.85 by Derek Mulcahy.Built against ntp3-5.90 on Solaris 2.5 using gcc 2.7.2.This code may be freely copied and used and incorporated in othersystems providing the disclaimer and notice of authorship arereproduced.-------------------------------------------------------------------------------Nigel's notes:1) Called tcgetattr() before modifying, so that fields correctly initialised   for all operating systems2) Altered parsing of timestamp line so that it copes with fields which are   not always ASCII digits (e.g. status field when battery low)-------------------------------------------------------------------------------Christopher's notes:MAJOR CHANGES SINCE V1.2 ======================== 1) Applied patch by Andrey Bray <abuse@madhouse.demon.co.uk>    2001-02-17 comp.protocols.time.ntp 2) Added WWVB support via clock mode command, localtime/UTC time configured    via flag1=(0=UTC, 1=localtime) 3) Added ignore resync request via flag2=(0=resync, 1=ignore resync) 4) Added simplified conversion from localtime to UTC with dst/bst translation 5) Added average signal quality poll 6) Fixed a badformat error when no code is available due to stripping     \n & \r's  7) Fixed a badformat error when clearing lencode & memset a_lastcode in poll    routine 8) Lots of code cleanup, including standardized DEBUG macros and removal     of unused code -------------------------------------------------------------------------------Author's original note:I enclose my ntp driver for the Galleon Systems Arc MSF receiver.It works (after a fashion) on both Solaris-1 and Solaris-2.I am currently using ntp3-5.85.  I have been running the code forabout 7 months without any problems.  Even coped with the change to BST!I had to do some funky things to read from the clock because it uses thepower from the receive lines to drive the transmit lines.  This makes thecode look a bit stupid but it works.  I also had to put in some delays toallow for the turnaround time from receive to transmit.  These delaysare between characters when requesting a time stamp so that shouldn't affectthe results too drastically....The bottom line is that it works but could easily be improved.  You arefree to do what you will with the code.  I haven't been able to determinehow good the clock is.  I think that this requires a known good clockto compare it against.-------------------------------------------------------------------------------Damon's notes for adjustments:MAJOR CHANGES SINCE V1.0======================== 1) Removal of pollcnt variable that made the clock go permanently    off-line once two time polls failed to gain responses. 2) Avoiding (at least on Solaris-2) terminal becoming the controlling    terminal of the process when we do a low-level open(). 3) Additional logic (conditional on ARCRON_LEAPSECOND_KEEN being    defined) to try to resync quickly after a potential leap-second    insertion or deletion. 4) Code significantly slimmer at run-time than V1.0.GENERAL======= 1) The C preprocessor symbol to have the clock built has been changed    from ARC to ARCRON_MSF to CLOCK_ARCRON_MSF to minimise the    possiblity of clashes with other symbols in the future. 2) PRECISION should be -4/-5 (63ms/31ms) for the following reasons:     a) The ARC documentation claims the internal clock is (only)        accurate to about 20ms relative to Rugby (plus there must be        noticable drift and delay in the ms range due to transmission        delays and changing atmospheric effects).  This clock is not        designed for ms accuracy as NTP has spoilt us all to expect.     b) The clock oscillator looks like a simple uncompensated quartz        crystal of the sort used in digital watches (ie 32768Hz) which        can have large temperature coefficients and drifts; it is not        clear if this oscillator is properly disciplined to the MSF        transmission, but as the default is to resync only once per        *day*, we can imagine that it is not, and is free-running.  We        can minimise drift by resyncing more often (at the cost of        reduced battery life), but drift/wander may still be        significant.     c) Note that the bit time of 3.3ms adds to the potential error in        the the clock timestamp, since the bit clock of the serial link        may effectively be free-running with respect to the host clock        and the MSF clock.  Actually, the error is probably 1/16th of        the above, since the input data is probably sampled at at least        16x the bit rate.    By keeping the clock marked as not very precise, it will have a    fairly large dispersion, and thus will tend to be used as a    `backup' time source and sanity checker, which this clock is    probably ideal for.  For an isolated network without other time    sources, this clock can probably be expected to provide *much*    better than 1s accuracy, which will be fine.    By default, PRECISION is set to -4, but experience, especially at a    particular geographic location with a particular clock, may allow    this to be altered to -5.  (Note that skews of +/- 10ms are to be    expected from the clock from time-to-time.)  This improvement of    reported precision can be instigated by setting flag3 to 1, though    the PRECISION will revert to the normal value while the clock    signal quality is unknown whatever the flag3 setting.    IN ANY CASE, BE SURE TO SET AN APPROPRIATE FUDGE FACTOR TO REMOVE    ANY RESIDUAL SKEW, eg:        server 127.127.27.0 # ARCRON MSF radio clock unit 0.        # Fudge timestamps by about 20ms.        fudge 127.127.27.0 time1 0.020    You will need to observe your system's behaviour, assuming you have    some other NTP source to compare it with, to work out what the    fudge factor should be.  For my Sun SS1 running SunOS 4.1.3_U1 with    my MSF clock with my distance from the MSF transmitter, +20ms    seemed about right, after some observation. 3) REFID has been made "MSFa" to reflect the MSF time source and the    ARCRON receiver. 4) DEFAULT_RESYNC_TIME is the time in seconds (by default) before    forcing a resync since the last attempt.  This is picked to give a    little less than an hour between resyncs and to try to avoid    clashing with any regular event at a regular time-past-the-hour    which might cause systematic errors.    The INITIAL_RESYNC_DELAY is to avoid bothering the clock and    running down its batteries unnecesarily if ntpd is going to crash    or be killed or reconfigured quickly.  If ARCRON_KEEN is defined    then this period is long enough for (with normal polling rates)    enough time samples to have been taken to allow ntpd to sync to    the clock before the interruption for the clock to resync to MSF.    This avoids ntpd syncing to another peer first and then    almost immediately hopping to the MSF clock.    The RETRY_RESYNC_TIME is used before rescheduling a resync after a    resync failed to reveal a statisfatory signal quality (too low or    unknown). 5) The clock seems quite jittery, so I have increased the    median-filter size from the typical (previous) value of 3.  I    discard up to half the results in the filter.  It looks like maybe    1 sample in 10 or so (maybe less) is a spike, so allow the median    filter to discard at least 10% of its entries or 1 entry, whichever    is greater. 6) Sleeping *before* each character sent to the unit to allow required    inter-character time but without introducting jitter and delay in    handling the response if possible. 7) If the flag ARCRON_KEEN is defined, take time samples whenever    possible, even while resyncing, etc.  We rely, in this case, on the    clock always giving us a reasonable time or else telling us in the    status byte at the end of the timestamp that it failed to sync to    MSF---thus we should never end up syncing to completely the wrong    time. 8) If the flag ARCRON_OWN_FILTER is defined, use own versions of    refclock median-filter routines to get round small bug in 3-5.90    code which does not return the median offset. XXX Removed this    bit due NTP Version 4 upgrade - dlm. 9) We would appear to have a year-2000 problem with this clock since    it returns only the two least-significant digits of the year.  But    ntpd ignores the year and uses the local-system year instead, so    this is in fact not a problem.  Nevertheless, we attempt to do a    sensible thing with the dates, wrapping them into a 100-year    window. 10)Logs stats information that can be used by Derek's Tcl/Tk utility    to show the status of the clock. 11)The clock documentation insists that the number of bits per    character to be sent to the clock, and sent by it, is 11, including    one start bit and two stop bits.  The data format is either 7+even    or 8+none.TO-DO LIST==========  * Eliminate use of scanf(), and maybe sprintf().  * Allow user setting of resync interval to trade battery life for    accuracy; maybe could be done via fudge factor or unit number.  * Possibly note the time since the last resync of the MSF clock to    MSF as the age of the last reference timestamp, ie trust the    clock's oscillator not very much...  * Add very slow auto-adjustment up to a value of +/- time2 to correct    for long-term errors in the clock value (time2 defaults to 0 so the    correction would be disabled by default).  * Consider trying to use the tty_clk/ppsclock support.  * Possibly use average or maximum signal quality reported during    resync, rather than just the last one, which may be atypical.*//* Notes for HKW Elektronik GmBH Radio clock driver *//* Author Lyndon David, Sentinet Ltd, Feb 1997      *//* These notes seem also to apply usefully to the ARCRON clock. *//* The HKW clock module is a radio receiver tuned into the Rugby *//* MSF time signal tranmitted on 60 kHz. The clock module connects *//* to the computer via a serial line and transmits the time encoded *//* in 15 bytes at 300 baud 7 bits two stop bits even parity *//* Clock communications, from the datasheet *//* All characters sent to the clock are echoed back to the controlling *//* device. *//* Transmit time/date information *//* syntax ASCII o<cr> *//* Character o may be replaced if neccesary by a character whose code *//* contains the lowest four bits f(hex) eg *//* syntax binary: xxxx1111 00001101 *//* DHD note:You have to wait for character echo + 10ms before sending next character.*//* The clock replies to this command with a sequence of 15 characters *//* which contain the complete time and a final <cr> making 16 characters *//* in total. *//* The RC computer clock will not reply immediately to this command because *//* the start bit edge of the first reply character marks the beginning of *//* the second. So the RC Computer Clock will reply to this command at the *//* start of the next second *//* The characters have the following meaning *//* 1. hours tens   *//* 2. hours units  *//* 3. minutes tens *//* 4. minutes units *//* 5. seconds tens  *//* 6. seconds units *//* 7. day of week 1-monday 7-sunday *//* 8. day of month tens *//* 9. day of month units *//* 10. month tens *//* 11. month units *//* 12. year tens *//* 13. year units *//* 14. BST/UTC status *//*      bit 7   parity *//*      bit 6   always 0 *//*      bit 5   always 1 *//*      bit 4   always 1 *//*      bit 3   always 0 *//*      bit 2   =1 if UTC is in effect, complementary to the BST bit *//*      bit 1   =1 if BST is in effect, according to the BST bit     *//*      bit 0   BST/UTC change impending bit=1 in case of change impending *//* 15. status *//*      bit 7   parity *//*      bit 6   always 0 *//*      bit 5   always 1 *//*      bit 4   always 1 *//*      bit 3   =1 if low battery is detected *//*      bit 2   =1 if the very last reception attempt failed and a valid *//*              time information already exists (bit0=1) *//*              =0 if the last reception attempt was successful *//*      bit 1   =1 if at least one reception since 2:30 am was successful *//*              =0 if no reception attempt since 2:30 am was successful *//*      bit 0   =1 if the RC Computer Clock contains valid time information *//*              This bit is zero after reset and one after the first *//*              successful reception attempt *//* DHD note:Also note g<cr> command which confirms that a resync is in progress, andif so what signal quality (0--5) is available.Also note h<cr> command which starts a resync to MSF signal.*/#include "ntpd.h"#include "ntp_io.h"#include "ntp_refclock.h"#include "ntp_calendar.h"#include "ntp_stdlib.h"#include <stdio.h>#include <ctype.h>#if defined(HAVE_BSD_TTYS)#include <sgtty.h>#endif /* HAVE_BSD_TTYS */#if defined(HAVE_SYSV_TTYS)#include <termio.h>#endif /* HAVE_SYSV_TTYS */#if defined(HAVE_TERMIOS)#include <termios.h>#endif/* * This driver supports the ARCRON MSF/DCF/WWVB Radio Controlled Clock *//* * Interface definitions */#define DEVICE          "/dev/arc%d"    /* Device name and unit. */#define SPEED           B300            /* UART speed (300 baud) */#define PRECISION       (-4)            /* Precision  (~63 ms). */#define HIGHPRECISION   (-5)            /* If things are going well... */#define REFID           "MSFa"          /* Reference ID. */#define REFID_MSF       "MSF"           /* Reference ID. */#define REFID_DCF77     "DCF"           /* Reference ID. */#define REFID_WWVB      "WWVB"          /* Reference ID. */#define DESCRIPTION     "ARCRON MSF/DCF/WWVB Receiver"#ifdef PRE_NTP420#define MODE ttlmax#else#define MODE ttl#endif