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OISTAR FieldBus TimeMaster - 23

Description

Driver for synchronizion of an Oceonics-Intersite Serial-data Timing And Routing (OISTAR) network to the QINSy UTC time.
When Pulse-Per-Second (PPS) support is used, the timing can be very accurate, although the accuracy is limited to 0.01 second by the number of decimals in the command to set the relative time (2).

The driver can only work properly when the connected OISTAR unit has been configured as "TimeMaster".
The same unit should also be configured as "Controller" (or "Master") in order to interpret local commands.
When the driver is started or reset, the date and time of the real time clock of the OISTAR fieldbus is set approximately to UTC using the local "Set Date" and "Set Time" commands.
When the driver is executing, the reply to the local "Request Status" command is used to monitor the difference between OISTAR fieldbus time and QINSy UTC time, and the OISTAR time is adjusted using the local "Set Relative Time" command.

Driver Information

Driver OISTAR FieldBus TimeMaster  Interface Type Serial Driver Class Type Interrogated
UTC Driver (question)   Input / Output Output Executable DrvOistarSynch.exe 10 
Related Systems
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Interfacing Notes

Configure the connected OISTAR unit as "TimeMaster" and "Controller", using the toggle switches on the front panel.
Configure the interfacing parameters of the OISTAR unit using the "OisFace" communication program.
Set the baud rate as high as possible. Make sure that RS-232 cable wiring to QINSy is bi-directional.

Database Setup

The time difference between the QINSy UTC time and the OISTAR fieldbus time can be monitored online. In order to do so, add a generic observation to the OISTAR system setup.
Leave the scale factor to 1. The observation is QPS time minus OISTAR time in seconds.
It's quality indicator is computed as the absolute value of the time difference times 100, i.e. the absolute time difference in units of 10 milliseconds, which is the OISTAR time resolution.
A negative value is an indication of a serial error in the previous update cycle.

Online

The quality indicator of the generic time difference observation can be used online as alert on the OISTAR performance. When online with the Controller, start up (or open) an Alert Display. Add a new "Raw Data Alert" and select the "quality indicator outside limit". Set lower limit to 0 (a negative value indicates a serial communication error) and upper limit to 2 or 3, when 20 ms (0.020 s), resp. 30 ms (0.030 s), is the maximum allowed time difference. Select OISTAR system and time difference observation and press "Finish" button.

It is also recommended to add an "I/O Alert" in order to check the data transmission between QINSy and the OISTAR "TimeMaster" unit. Set the timeout value to at least 10 times the update rate entered in DB Setup plus 1 second, with a minimum of 11 seconds, because of the minimum allowed update rate of 1.0 second.

Drivers IO Notes

Command line parameters "10" <LF> or "13" <CR> in the "drivers.io" file can set the EOM terminator.

Additional Information

DrvOistarSynch time tagging

// sensor      OISTAR      OISTAR      COM port    driver
// sends       timetags    sends       receives    timetags
// message     message     message     message     message
// 
//  |     A     |     B     |     C     |     D     |
//  + - - - - - + - - - - - + - - - - - + - - - - - + - > 
// 
// DrvOistarSynch assumes that all intervals are constant
// A, B and D are unknown (very small); C can be computed
// using interfacing parameters (latency is not applied).
// 
// DrvOistarSynch OISTAR must filter all sensor messages;
// only status messages (and bus error messages) allowed!

DrvOistarSynch update rates

If the absolute difference in time between the QINSy UTC time and the OISTAR fieldbus time is greater than 0.025 second, the driver update rate is set to the initial OISTAR FieldBus TimeMaster system update rate from DB Setup, with a minimum rate of 1.0 second, in order to not stress the OISTAR "TimeMaster" unit.

If the difference is between 0.025 and 0.010 second, the driver update rate is set to 2.5 times the initial update rate. If the difference is less than 0.010 second, the driver update rate is set to 10 times the initial update rate.

If the absolute time difference is greater than 0.0075 second (0.010 seconds is the OISTAR time resolution), a "Relative Time Set" local command is issued, except when the OISTAR fieldbus time within one second from an integral minute, because it has been seen during tests that the OISTAR can set a wrong time then. However, if the time difference is greater than 2.0 seconds, "Date Set" and "Time Set" commands are sent.

All the time tags in the QINSy output commands first are corrected for the number of bytes that are sent.

OISTAR "TimeMaster" LED's

OISTAR LED L5 (bottom LED upper left row) should be red to indicate that OISTAR unit is acting as Time Master. If all is well, i.e. all time differences are below 10 ms, the LED's to indicate user port data transfer (L1, top LED upper left row, and L2, top LED upper right row) will only flash once every 10 seconds.