Frequently Asked Questions
about the White Rabbit switch.
Connecting the switch to an external GPS receiver
Q: What are the advantages of using external GPS signals or are there any disadvantages of not using them and leave the connectors open?
A: You mainly get two things:
- A more stable oscillator for the master switch and therefore for all the network.
- A GPS/UTC/TAI-related time scale. This is important if you want to relate your events to official time or if you want to avoid re-starting your time scale at 1 Jan 1970 (or something like that) every time you reboot the switch. Two events seen in a WR network at very different times could have very similar time stamps in there was a switch reboot in between. Syncing to GPS time on reboot avoids that.
Q: When connecting the GPS-PPS or the 10 MHz GPS clock to the WhiteRabbit Switch, do I have to change/configure anything?
A: Yes, it is documented
Q: The last paragraph of the document above mentions HAL messages and RT log. I find HAL messages but what is meant by RT log and where to find it?
A: By the RT (i.e. realtime) log we mean the messages generated by the LM32 CPU inside the Virtex FPGA. They may provide useful information for debugging the timing subsystem. They can be viewed by connecting a serial terminal to the the front left USB port (up to v. 3.2 switches) or the "FPGA test" USB port in the rear (newer switches). RS232 parameters are 115200, 8N1.
General questions
Q: does the switch comply to CE regulations (EMC)?
A: It is. The company Seven Solutions has performed extensive EMC tests on the switch.
Q: If I don’t participate in WR workshop meetings, is the presentation material still available?
A: All we do is public. All information from the workshops is public.
Q: How can I test White Rabbit equipment? Or I can I buy some test equipments from your company?
A: CERN is not a company, but a publicly funded intergovernemental
organization. We develop the technology but don't produce the equipment,
we buy WR switches from commercial vendors. Anyone can produce a WR
switch as all the sources are on our
pages (just have a careful
look at the wiki, sub-projects, ets... )
For example, there is wiki page about the WR switch on which
you can find the companies that are involved in switch development and
the companies from which you can buy a WR switch (Commercial producers,
at the bottom). On the wiki page about SPEC
card (an example of WR Node)
you will find companies producing SPEC cards.
For starting to play with WR technology, very soon a "WR started kit"
will be available, see WR node wiki page for
details.
Q: Should green and orange LEDs be lit when copper SFP is used even without Ethernet cable plugged in ?
A: Yes, that is the normal behavior with most of the copper SFPs. Even after unplugging Ethernet cable the copper SFP fakes an active connection so green LED is ON and orange may be blinking.
24 January 2013