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I am fearful of soldering anything to the FPGA because it may be used for many other projects.
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Where are the resistors? On the BGA pads, or away from the FPGA? If they are away from the FPGA, then you should not be scared to solder :)
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My pin planner looks like garbage. I think there are 3 levels of (n)s.
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The pin planner does not technically need any (n)s. If you define the positive side as LVDS, then the negative side is inferred. You can always copy the project to a new folder, and then delete constraints until you either break something, or clean it up.
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However, the darn thing works. I tested the speeds up to 50 MHz in (300 MHz out) and without using termination, the signals appear to arrive at the FPGA correctly. After the code is complete I will do extensive testing, and if we require 100 Ohm resistors, we will (painfully) attach them.
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Look at the signals at the FPGA with an oscilloscope and the signals probably look nasty :)
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Again, thank you for your help. I don't know how it's working, like I said pin planner looks like garbage. But it is. Moving on. Not touching it.
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That is fine. However, if you start calculating the performance of your ADC, eg., INL and DNL, then you may be getting bit errors over the LVDS links that make things look worse.
The bottom line is, do not be afraid of soldering. If you've never done it before, then go find a dead PC, pull out a PCI board, and start removing parts from that and then soldering them back on again. Once you feel comfortable doing that, you can add the terminations onto the DE115 board :)
Cheers,
Dave
Honored Contributor
