Miles Leitch Cape Town Area, South Africa Driver at Safari Ltd ® 0 connection See Miles's complete profile on Linkedin and connect.
| Documents Home :: 4.1.2 :: refclock.htm | Download |
| Advanced Search |
Reference Clock Drivers
Master Time Facility at the UDel Internet ResearchLaboratory:Leitch's most successful season to date would be the 2016 season, where he scored one win, three podiums and third overall in the driver standings. Following this, Leitch secured a drive in the Formula 4 United States Championship for 2017. After a strong campaign, Leitch returned to New Zealand and would contend his fifth consecutive season in. Shane van Gisbergen has claimed pole position on his return to the Castrol Toyota Racing Series at Hampton Downs Motorsport Park. The Red Bull-backed driver set a 1:30.231s on his final flying lap.
Support for most of the commonly available radio and modem reference clocksis included in the default configuration of the NTP daemon for Unix ntpd.Individual clocks can be activated by configuration file commands, specificallythe server and fudge commands described in the ntpd program manual page. The following discussionpresents Information on how to select and configure the device drivers ina running Unix system.
Many radio reference clocks can be set to display local time as adjustedfor timezone and daylight saving mode. For use with NTP the clock must beset for Coordinated Universal Time (UTC) only. Ordinarily, these adjustmentsare performed by the kernel, so the fact that the clock runs on UTC willbe transparent to the user.
Leitch Driver Ed
Radio and modem clocks by convention have addresses in the form 127.127.t.u,where t is the clock type and u is a unit number in the range0-3 used to distinguish multiple instances of clocks of the same type. Mostof these clocks require support in the form of a serial port or special busperipheral, but some can work directly from the audio codec found in some workstations. The particular device is normally specified by adding a softlink /dev/deviceu to the particular hardware device involved,where u correspond to the unit number above.
Most clock drivers communicate with the reference clock using a serialport, usually at 9600 bps. There are several application program interfaces(API) used in the various Unix and NT systems, most of which can be detectedat configuration time. Thus, it is important that the NTP daemon and utilitiesbe compiled on the target system or clone. In some cases special featuresare available, such as timestamping in the kernel or pulse-per-second (PPS)interface. In most cases these features can be detected at configurationtime as well; however, the kernel may have to be recompiled in order forthem to work.
The audio drivers are a special case. These include support for the NISTtime/frequency stations WWV and WWVH, the Canadian time/frequency stationCHU and generic IRIG signals. Currently, support for the Solaris and SunOSaudio API is included in the distribution. It is left to the volunteer corpsto extend this support to other systems. Further information on hookup, debugging and monitoring is given in the Audio Drivers page.
The local clock driver is also a special case. A server configured withthis driver can operate as a primary server to synchronize other clientswhen no other external synchronization sources are available. If the serveris connected directly or indirectly to the public Internet, there is somedanger that it can adversely affect the operation of unrelated clients. Carefullyread the Undisciplined Local Clock page and respectthe stratum limit.
The local clock driver also supports an external synchronization sourcesuch as a high resolution counter disciplined by a GPS receiver, for example.Further information is on the External Clock Disciplineand the Local Clock Driver page.
Driver Calibration
Some drivers depending on longwave and shortwave radio services need toknow the radio propagation time from the transmitter to the receiver, whichcan amount to some tens of milliseconds. This must be calculated for eachspecific receiver location and requires the geographic coordinates of boththe transmitter and receiver. The transmitter coordinates for various radioservices are given in the Stations, Frequencies and Geographic Coordinates page. Receiver coordinates can be obtained or estimated fromvarious sources. The actual calculations are beyond the scope of this document.
When more than one clock driver is supported, it is often the case thateach shows small systematic offset differences relative to the rest. To reducethe effects of jitter when switching from one driver to the another, it isuseful to calibrate the drivers to a common ensemble offset. The enablecalibrate configuration command in the Miscellaneous Options page is useful for this purpose. The calibration function canalso be enabled and disabled using the ntpdc program utility.
Most clock drivers use the time1 value specified in the fudgeconfiguration command to provide the calibration correction when this cannotbe provided by the clock or interface. When the calibration function is enabled,the time1 value is automatically adjusted to match the offset ofthe remote server or local clock driver selected for synchronization. Ordinarily,the NTP selection algorithm chooses the best from among all sources, usuallythe best radio clock determined on the basis of stratum, synchronizationdistance and jitter. The calibration function adjusts the time1values for all clock drivers except this source so that their indicated offsetstend to zero. If the selected source is the kernel PPS discipline, the fudge time1 values for all clock drivers are adjusted.
The adjustment function is an exponential average designed to improveaccuracy, so the function takes some time to converge. The recommended procedureis to enable the function, let it run for an hour or so, then edit the configurationfile using the time1 values displayed by the ntpq utilityand clockvar command. Finally, disable the calibration functionto avoid possible future disruptions due to misbehaving clocks or drivers.
Performance Enhancements
In general, performance can be improved, especially when more than oneclock driver is supported, to use the prefer peer function described in theMitigation Rules and the prefer Keywordpage. The prefer peer is ordinarily designated the remote peer or local clockdriver which provides the best quality time. All other things equal, onlythe prefer peer source is used to discipline the system clock and jitter-producing 'clockhopping' between sources is avoided. This is valuable when more thanone clock driver is present and especially valuable when the PPS clock driver(type 22) is used. Support for PPS signals is summarized in the Pulse-per-second (PPS) Signal Interfacing page.
Where the highest performance is required, generally better than one millisecond,additional hardware and/or software functions may be required. Kernel modificationsfor precision time are described in the A Kernel Modelfor Precision Timekeeping page. Special line discipline and streams modules for use in capturing precision timestamps are described in the Line Disciplines and Streams Drivers page.
Comprehensive List of Clock Drivers
Following is a list showing the type and title of each driver currentlyimplemented. The compile-time identifier for each is shown in parentheses.Click on a selected type for specific description and configuration documentation,including the clock address, reference ID, driver ID, device name and serialline speed, and features (line disciplines, etc.). For those drivers withoutspecific documentation, please contact the author listed in the Copyright Notice page.
Leitch Driver License
Type 1 Undisciplined Local Clock (LOCAL)
Type 2 Trak 8820 GPS Receiver (GPS_TRAK)
Type 3 PSTI/Traconex 1020 WWV/WWVH Receiver (WWV_PST)
Type 4 Spectracom WWVB and GPS Receivers (WWVB_SPEC)
Type 5 TrueTime GPS/GOES/OMEGA Receivers (TRUETIME)
Type 6 IRIG Audio Decoder (IRIG_AUDIO)
Type 7 Radio CHU Audio Demodulator/Decoder (CHU)
Type 8 Generic Reference Driver (PARSE)
Type 9 Magnavox MX4200 GPS Receiver (GPS_MX4200)
Type 10 Austron 2200A/2201A GPS Receivers (GPS_AS2201)
Type 11 Arbiter 1088A/B GPS Receiver (GPS_ARBITER)
Type 12 KSI/Odetics TPRO/S IRIG Interface (IRIG_TPRO)
Type 13 Leitch CSD 5300 Master Clock Controller (ATOM_LEITCH)
Type 14 EES M201 MSF Receiver (MSF_EES)
Type 15 * TrueTime generic receivers
Type 16 Bancomm GPS/IRIG Receiver (GPS_BANCOMM)
Type 17 Datum Precision Time System (GPS_DATUM)
Type 18 NIST Modem Time Service (ACTS_NIST)
Type 19 Heath WWV/WWVH Receiver (WWV_HEATH)
Type 20 Generic NMEA GPS Receiver (NMEA)
Type 21 TrueTime GPS-VME Interface (GPS_VME)
Type 22 PPS Clock Discipline (PPS)
Type 23 PTB Modem Time Service (ACTS_PTB)
Type 24 USNO Modem Time Service (ACTS_USNO)
Type 25 * TrueTime generic receivers
Type 26 Hewlett Packard 58503A GPS Receiver (GPS_HP)
Type 27 Arcron MSF Receiver (MSF_ARCRON)
Type 28 Shared Memory Driver (SHM)
Type 29 Trimble Navigation Palisade GPS (GPS_PALISADE)
Type 30 Motorola UT Oncore GPS (GPS_ONCORE)
Type 31 Rockwell Jupiter GPS (GPS_JUPITER)
Type 32 Chrono-log K-series WWVB receiver (CHRONOLOG)
Type 33 Dumb Clock (DUMBCLOCK)
Type 34 Ultralink WWVB Receivers (ULINK)
Type 35 Conrad Parallel Port Radio Clock (PCF)
Type 36 Radio WWV/H Audio Demodulator/Decoder(WWV)
Type 37 Forum Graphic GPS Dating station (FG)
Type 38 hopf GPS/DCF77 6021/komp for Serial Line(HOPF_S)
Type 39 hopf GPS/DCF77 6039 for PCI-Bus (HOPF_P)
Type 40 JJY Receivers (JJY)
Type 44 NeoClock4X DCF77 / TDF receiver
* All TrueTime receivers are now supported by one driver, type 5. Types15 and 25 will be retained only for a limited time and may be reassignedin future.
Additional Information
Mitigation Rules and the prefer Keyword
Debugging Hints for Reference Clock Drivers
A Kernel Model for Precision Timekeeping
Line Disciplines and Streams Drivers
Reference Clock Audio Drivers
Pulse-per-second (PPS) Signal Interfacing
How To Write a Reference Clock Driver
Invercargill’s Brendon Leitch will take the wheel of a Castrol Toyota Racing Series car one more time when he steps aboard to try and add his name to the New Zealand Grand Prix Trophy later this month.
Twenty five year old Leitch is the most experienced TRS racer in the world having competed in TRS championships in the first generation FT40 car and the more recent FT50. He has also tested the current FT60 car and has extensive experience in the Tatuus chassis having raced last season in the Asia Formula Three Championship, a category that utilises the same chassis, albeit on different tyres. Leitch also has extensive GT expertise and is a former Lamborghini Junior Driver.
Post-lockdown in New Zealand Brendon also renewed his driving partnership with Christina Orr-West as the pair took on more contemporary GT machinery in their Dayle ITM Racing Audi R8 LMS on their way to podium finishes in the 2020 South Island Endurance Series.
A veteran of New Zealand Grand Prix competition and vastly experienced around the Hampton Downs circuit, Leitch is confident he can be a factor when he and the rest of the talent-packed field take to the North Waikato track for first practice on Friday January 22nd.
“It’s been disappointing to effectively say goodbye to my international drives because of the pandemic and the associated international travel problems that come with a situation like that,” he explained.
“Dayle ITM has long been my major backer and the opportunity has come up to do the Grand Prix one more time, this time in the current car but with the familiar yellow backing and I’m looking forward to flying the flag and racing in TRS once again.
Leitch Drivers
“There’s absolutely no reason why we cannot be competitive from the first session of the event. I have a good idea of where we need to go with set up of the car and what needs to be done in the limited time we will have to get the cars dialled in before the Grand Prix itself. There are some massive names competing and it will be cool to be part of it.”
Leitch Driver License Test
Shane van Gisbergen, Greg Murphy, Daniel Gaunt, Chris van der Drift and up and coming stars Billy Frazer, Kaleb Ngatoa and Matthew Payne are amongst those set to take the start on the long circuit at Hampton Downs, as well as the iconic Kenny Smith who will make an unprecedented 50th start in the 66th running of the event.
Billed this year as the Race of Champions, the 2021 New Zealand Grand Prix will be one of the biggest for major names since Bruce McLaren himself was behind the wheel.
The MotorSport New Zealand-sanctioned event doubles as the opening round of the championship. A joint venture by Hampton Downs and Speed Works Events, it will run over the weekend of January 22nd-24th with practice, qualifying and two races for drivers before the New Zealand Grand Prix itself on Sunday 24th over 28 laps of the circuit.
A legendary list of previous winners includes Stirling Moss, Prince Bira, Jack Brabham, John Surtees, Graham Hill, Jackie Stewart and legendary Kiwi racers Bruce McLaren and Chris Amon. More recently, it has been won by current F1 drivers Lando Norris and Lance Stroll.
It will be the first time the Grand Prix has been held at the North Waikato circuit and the first time any Castrol Toyota Racing Series event has been held on the longer and more challenging 4km international format track which has ten corners and a current lap record of 1 minute 27.637 seconds.