xConnect over twisted pair Topic is solved

[srinie]

Hi Mon2,
This sliceCARD is not yet fully productized and hence I am not sure if we can publish this as a hardware board.

May I request you to raise a support ticket and we can see how best we can serve you.

Thanks.

[mon2]

Hi srinie. Thanks for your reply. We have opened a ticket for the request of these details. Also forwarded a few comments on the posted application note for review.

For our similar project we are considering the following - perhaps you may be interested to do something along this line as well ?

To allow for either a straight through or cross over RJ45 cable to interconnect XMOS boards, consider to apply 2 of the

Fairchild P/N FIN1049MTCX
or
TI P/N DS90LV049 LVDS devices.

One of the DS90LV049 will be wired up to support the straight through RJ45 connections.

The other DS90LV049 will be wired up to support the cross over cable style of the RJ45 connections.

Only one of the two DS90LV049 devices will be active at anytime.

Then enable one or the other DS90LV049 devices based on the interconnect RJ45 cable wiring. For now, we are considering to use a small jumper to enable / disable the respective DS90LV049 package but reviewing if we can automate the selection based on the cable wiring - this is work in progress.

In the end, if the user throws the jumper on one of the 2 mated LVDS slice boards then they are free to use either style of RJ45 cabling :) This will make the LVDS board more user friendly.

Also, from your posted LVDS appnote:

1) are the raised communication errors during operation to be expected based on the posted code / delays in the communication ? That is, if we tweak the communication delays (to slow down) then the errors will be eliminated ?

2) please consider to document the quality & length of the cable used in the project. Specifically, if we consider CAT5 vs CAT6 - will CAT6 reduce / remove the posted errors ?

3) Can you comment on the max length of the cables used for such interconnect without errors ?

We are exploring some designs which will allow for quick stacking, etc. of XMOS processors using the LVDS interface.

Thanks.

Kumar

[srinie]

Hi Kumar,
We should be in sync to the point that xCONNECT `tx and rx` (cross-over) pins should be connected.

The RJ45 type LVDS connector demo uses a cross-over cable and the manual connection also ensures tx-rx connect.

Some feedback to your queries:
- posted code does not introduce any explicit communication errors; it repeatedly sends data tokens, control tokens and times out periodically.
- establishes the link after the timeout and resumes the communication using the credit exchanges (at the link layer of xCONNECT)
- we ve used cat5 cross-over cable, < 1 m length; have not tried with varied lengths

Good luck for your designs.

Cheers.

[mon2]

Thanks for your prompt reply Srinie.

If we understand correctly, using 2 wire mode as the links, this will result in all 8 wires (due to each signal being converted to LVDS) being used on the (common) RJ45 connector (8p8c).

Respectively, your LVDS documentation shows a single CAT5 cable in the setup photo so the cable is not using a common ground between the linked slicekits ? Just wondering if the use of ground with the cross over CAT5 cable would assist in reducing the errors.