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Visitor
Visitor
401 Views
Registered: ‎05-23-2020

Using LVDS port

I have a single ended SMA coming from a device and I want to use it in my FPGA. Unfortunately Vivado only allows differential signals to use the LVDS ports such as SMA. How can I overcome this problem?

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Voyager
Voyager
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Registered: ‎08-02-2019

Hi @AliAlra ,

In Vivado you can easily convert Single Ended Signals to LVDS and vice versa(it must be input or output parameters and need to be located in top modul of your Vivado Design .

To do it, you can use :

i_buffer : IBUFDS
port map (
   O => single_input,
   I => diff_input_p,
   IB => diff_input_n
);

OBUFDS #(
.IOSTANDARD("LVDS_25") // Specify the output I/O standard
) OBUFDS_inst (
.O(ServoDataToSOCp), // Diff_p output (connect directly to top-level port) (p type differential o/p)
.OB(ServoDataToSOCn), // Diff_n output (connect directly to top-level port) (n type differential o/p)
.I(Servo_Data) // Buffer input (this is the single ended standard)
);

Saban

 

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Visitor
Visitor
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Registered: ‎05-23-2020

I understand that but my problem is that my port coming in from outside of the board is single ended but it is an SMA signal. and the only ports in my board are LVDS. Therefore I want to us a single ended signal coming and allow it to use an LVDS pin

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364 Views
Registered: ‎01-22-2015

@AliAlra 

I see that you talked with gnarahar about this in the following post.

https://forums.xilinx.com/t5/Serial-Transceivers/FMC-ZCU102/m-p/1111136#M7897

Do you have the same problem or is this a new problem?

If it is a new problem then tell us exactly which pins on ZCU102 board you are trying to connect with.

Cheers, Mark

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Visitor
Visitor
361 Views
Registered: ‎05-23-2020

Same problem except this time I realized that I do not have to use a GT wizard. and the main problem is that I only have Single ended SMAs that need to be used in an LDVS pin

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340 Views
Registered: ‎06-21-2017

Does the port have an external termination resistor?  If not, why can't you give the pin a single ended IO type and use it as single ended?

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Visitor
Visitor
335 Views
Registered: ‎05-23-2020

All the pins of ZCU102 that are connected to SMAs are only LVDS

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333 Views
Registered: ‎01-22-2015

@AliAlra 

I only have Single ended SMAs that need to be used in an LDVS pin..

If you are talking about general purpose IO pins on the FPGA then there is no such thing as an "LVDS pin".   Your FMC extender board and the description of your FMC connector may call them LVDS pins.  However, in these cases, they are probably just wires that you can use anyway you want.  That is, each of the two LVDS wires can be used for single-end signals.

Please tell us exactly how you want to route from the FMC extender board to the FPGA.  That is, tell us the part# for your FMC board, the SMA connector on the FMC board, the pins on the FMC connector you want to use, and the FPGA pin number that they connect with.

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Visitor
Visitor
324 Views
Registered: ‎05-23-2020

The FPGA pin is G27 or E31 for example to use for the SMA input (M2C). As for the FMC card it is this one:

 

http://www.hitechglobal.com/FMCModules/FMC_SMA_LVDS.htm

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307 Views
Registered: ‎01-22-2015

@AliAlra 

Those are pins used by the GT transceivers and @gnarahar has already told you not to use them.

Look again at connections on your FMC extender board and try to find connections leading to a User IO Pin of the FPGA on the ZCU102 board.  User IO Pins are described by Table 1-4 of UG1075(v1.9).

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Visitor
Visitor
298 Views
Registered: ‎05-23-2020

But the thing is that they can be used by a user depending on how you use them. When I put in two inputs as differential signals and add a IBUFDS after that then Iit allows me to use them and I can use them just fine. But for my current application I need it for a single ended SMA not differential and if it is as you say then give me another pin that I can use SMA with.

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Teacher
Teacher
149 Views
Registered: ‎03-31-2012

Hi Ali,

as other people have tried to tell you the pins you're trying to use have a dedicated purpose as part of transceiver and they can't be used individually. If the pair were just a regular IO pair you could treat each one as single ended but not with the pair you have. They go directly to an analog macro inside the chip and there is no direct path to the fabric.

- Please mark the Answer as "Accept as solution" if information provided is helpful.
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