Converting the Zybo Standar Pmod

[Tarik Loukili]

Hi,

If I replace the 200 ohms used in series with the Standard Pmod with a 0 ohms resistors (shunt resistors) will that make my Standard Pmod a High Speed Pmod.

Note: Please answer this question only if you know what you are talking about, don't copy and past part of the Zybo manual in the replay.

Thank you

Tarik

[hamster]

If I replace the 200 ohms used in series with the Standard Pmod with a 0 ohms resistors (shunt resistors) will that make my Standard Pmod a High Speed Pmod[?]

No.

[hamster]

All of the Zybo's PMODs there are also clamping diodes (see page 1 of the schematics at http://digilentinc.com/Data/Products/ZYBO/ZYBO_sch_VB.3.pdf ). You should plan on removing these too as they will not have been specified for use on high speed data lines.

How fast do you need to run the pins at? I've never had much success after about 250Mb/s though pin-header style connectors when running board-to-board, and I've even had problems as low as 25Mb/s when short cables are involved (e.g using a PMOD-AD1 over a 150mm cable).

(Note - all of these answers are true, and not included in the Zybo manual... ).

[Tarik Loukili]

I m trying to build a stereo camera, communicating with the image sensors @ 25MHz. each camera will need two PMOds. when I used one of the High speed and a standard one I end up with some weird colors and noise in the images. on the other hand when I use two High speed PMOds everythign works fine

Tarik

[Tarik Loukili]

what type are the diodes used with the High Speed PMOds ? if they are different can I get the type so I can replace them ?

Tarik

[hamster]

I've just had a look at the Genesys2, Nexys Video, Nexys 4 DDR and Zybo scnematics, and the differential PMODs all have 0 Ohm resistors, followed with (what I assume are zener) diodes for over voltage protection. The single ended PMODs all have 200 ohm resistors on the pins.

So I think you are correct - if you replace the resistors with 0 Ohm, leave the diodes in place, that will be the closest you get to to it being a high speed PMODs, However, they will not be differential pairs, and if you want to run at very high speed (e.g. 100s of Mb/s) the pins being single ended and extra capacitance form the diodes might be problematic - but then so will the connectors, and the PCB traces and everything else!

[Tarik Loukili]

thank you. Can you send me the BOM that will help do some verification.

Once I get the BOM I think I will go ahead and swap the resistors, it is worth trying. with a 25MHz I may not having issues with matching impedance. fingers cross :-)

Tarik

[TommyK]

Hi Tarik,

Unfortunately we cannot release the BOM for our products. I can tell you any specific part number though. The Avnet part number for the diode is NSQA6V8AW5T2. 

 

Regards,

Tommy

[Rahul Soni]

 

One of our  customer has design the custom board based with reference to Zybo board and they need support on part number of resistor and capacitor.

How can  I get the list of resister part number and capacitor part number

Can you please help ?

[jpeyron]

Hi @Rahul Soni,

What specific capacitor and resistor are you wanting information about.

cheers,

Jon