How to make a 7 device RTSI cable

[MDN]

I am currently trying to synchronize seven M-Series PCI-6224 cards via the RTSI bus. Unfortunately, NI only sells cables for up to 5 devices.

Does NI build custom RTSI cables for more devices?

Can you provide the part numbers so that I can build my own RTSI cable?

Thank you.

[Salvador_Santolucito]

Hi MDN,

The RTSI lines on your DAQ boards will only work within a certain range.  Our boards have been tested with up to 5 boards on the RTSI line.  However, adding more boards may yield unexpected results.  The added load on the RTSI lines would likely degrade the signals.

If you wish to synchronize a large number of devices, I would suggest that you go with a PXI system.  Using PXI, you can synchronize many boards without the headache of building your own RTSI cable and wondering whether or not it will work. 

If you are absolutely determined to build your own RTSI cable, the manufacturer of the connectors is 3M.  The part number for the inner connectors is 3421-6000 and the part number for the outer (closed end) connectors is 3421-7000.  The cable is a 20 pin ribbon type.  I would like to remind you that the use of a home-made RTSI cable is unsupported and National Instruments will NOT be able to guarantee your results.

-Sal

[MDN]

Salvador,

Thank you for your reply.

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@salvador Santolucito wrote:

The RTSI lines on your DAQ boards will only work within a certain range.  Our boards have been tested with up to 5 boards on the RTSI line.  However, adding more boards may yield unexpected results.  The added load on the RTSI lines would likely degrade the signals.

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Don't the RTSI lines use buffers to prevent loading effects? The cable length will probably be about as long as the extended 5 device cable that NI sells since all of my cards are in adjacent PCI slots.

I was wondering why this limitation isn't specified in the M-Series PCI card documentation. I've never seen anything in the specifications that would indicate a limitation on the number of shared devices on the RTSI bus.

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If you wish to synchronize a large number of devices, I would suggest that you go with a PXI system.  Using PXI, you can synchronize many boards without the headache of building your own RTSI cable and wondering whether or not it will work.

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Unfortunately, we've already upgraded our system on the PCI platform. Investing in an additional PXI system would be prohibitively expensive. Although the sales representative recommended the PXI system, he never indicated a problem with having too many PCI cards sharing the same bus.

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If you are absolutely determined to build your own RTSI cable, the manufacturer of the connectors is 3M.  The part number for the inner connectors is 3421-6000 and the part number for the outer (closed end) connectors is 3421-7000.  The cable is a 20 pin ribbon type.  I would like to remind you that the use of a home-made RTSI cable is unsupported and National Instruments will NOT be able to guarantee your results.

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The connector you specified is a 34 pin connector and so presumably one would use a 34 pin ribbon cable. I assume that this was a typo.

[MDN]

Has anyone tried using more than 5 devices on the RTSI bus? If so, what were the results?

[Salvador_Santolucito]

Sorry about that.  The correct part numbers are:

3M 3414-6000 (open end)

and

3M 3414-7000 (closed end)

It uses a 34 ribbon pin cable.

-Sal

[tenpete]

It happens that and old floppy drive cable uses a matching 34pin connector.  I have been successful at canalizing a few of these connectors and replacing them on the ribbon cable at the preferred spacing and making up my own cable.  PC board spacing is 20mm but 30 to 40 mm connector spacing will allow for "adjustment". Warning: the floppy drive cable connectors are not near the quality that NI uses and they take some care and to snap apart and replace without breaking.  Use a vise to squarely repress them onto the cable.

[GretchenSkellyZimmer]

MDN - were you successful in acquiring data from 7 devices reliably?  Did NI MAX allow you to add more than 5 devices to the RTSI cable?

[MDN]

No, I limited my channel count to 5 cards. Also, that was about 15 years ago now.