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Participant watman
Participant
14,111 Views
Registered: ‎05-19-2010

IO standard compatible with SLVS-200 on Spartan-6

I want to use a particular CMOS image sensor with a Spartan-6 FPGA, but the IO standard is not on the list of supported standards for Spartan-6. I don't have full specifications for the interface either due to NDAs taking a long time, so I'm hoping someone knows already if it is compatible with a supported standard.

 

The interface is the MIPI camera interface with "D-PHY" physical layer, which uses the SLVS-200 IO standard.

I only need to receive data as the control interface is separate.

The specifications I could find about SLVS-200 as used in D-PHY are:

 

unidirectional DDR source synchronous serial link, 80Mbps to 1Gbps

differential clock+data (4 lines min), 400mV pk-pk swing with 200mV common mode voltage

 

Some good information is here:

http://www.edn.com/article/518242-Implementing_an_SLVS_transceiver.php

 

Looking at the Spartan-6 DC and Switching Characteristics only PPDS supports a 200mV common mode voltage, and only just. The differential voltage looks ok, but I don't know if there are any other differences that would be a problem.

 

The other option I guess would be to AC couple it and move the signals to a higher common mode voltage, then use LVDS inputs.

I'd rather not though, as I don't know yet if the signal is DC-balanced.

 

Any thoughts?

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10 Replies
Teacher eteam00
Teacher
14,109 Views
Registered: ‎07-21-2009

Use the force, Watman!

... the IO standard is not on the list of supported standards for Spartan-6. I don't have full specifications for the interface either due to NDAs taking a long time, so I'm hoping someone knows already if it is compatible with a supported standard.

 

You are asking someone to divulge information covered by a NDA.  If this information can be disclosed without a NDA, then the sensor manufacturer should be the one to make this determination and make the disclosure.

 

I suggest you go through proper channels to obtain this information.  Describe your need in detail -- including the schedule and technology selection requirements of your project -- to the image sensor sales contact or distributor.  The sales guy has the incentive to make you (the customer) happy.

 

Going around the manufacturer's NDA may very well land you 'in hot water', so to speak.  My advice is to ask the mfr or disti for help, or simply wait.  Also, bring this problem to your project manager's attention (provide the PM with a clearly written explanation of what you need and why you need it) -- maybe the 'very important' managers of the customer hold sway with the 'very important' managers of the manufacturer.  You cannot threaten to switch to another vendor for millions and millions of sensors, but your manager's manager's manager might.

 

-- Bob Elkind

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Participant watman
Participant
14,087 Views
Registered: ‎05-19-2010

Re: Use the force, Watman!

You are asking someone to divulge information covered by a NDA.  If this information can be disclosed without a NDA, then the sensor manufacturer should be the one to make this determination and make the disclosure.
Perhaps I worded it poorly, but I'm not asking for information which is covered by an NDA. The NDA will be completed soon I hope and I will get full data, but for now I'm assuming that since the MIPI website specifies SLVS-200 then the 200mV common mode, 400mV p-p differential I found is correct.
My question is about the FPGA side of things: given these electrial parameters, can I interface directly with a Spartan-6. From looking at the datasheet it seems that this is juuust in the range of the PPDS IO standard, but I am not sure if there are other things to consider besides common mode and differential voltages.
I will of course ask the sensor manufacturer, but people on this forum will be much more familiar with the Spartan-6 input standards.
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Teacher eteam00
Teacher
14,084 Views
Registered: ‎07-21-2009

Re: Use the force, Watman!

200mV common mode, 400mV p-p differential

 

Are these min, max, or nominal values?

 

Per DS162, Table 10, the only differential input IOSTANDARDs which have a minimum common mode voltage (VICM) as low as 200mV are PPDS_33 and PPDS_25.  They both have a maximum differential input voltage (VID) of 400mV.  I don't think exceeding the VID spec will fry the inputs, but it might result in reduced input bandwidth.

 

Do you see where min vs. max vs. nominal might be important distinctions to make?

 

You always have the option of analogue circuit simulation, using the Spartan-6 IBIS models.

 

-- Bob Elkind

SIGNATURE:
README for newbies is here: http://forums.xilinx.com/t5/New-Users-Forum/README-first-Help-for-new-users/td-p/219369

Summary:
1. Read the manual or user guide. Have you read the manual? Can you find the manual?
2. Search the forums (and search the web) for similar topics.
3. Do not post the same question on multiple forums.
4. Do not post a new topic or question on someone else's thread, start a new thread!
5. Students: Copying code is not the same as learning to design.
6 "It does not work" is not a question which can be answered. Provide useful details (with webpage, datasheet links, please).
7. You are not charged extra fees for comments in your code.
8. I am not paid for forum posts. If I write a good post, then I have been good for nothing.
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Participant watman
Participant
14,080 Views
Registered: ‎05-19-2010

Re: Use the force, Watman!

Those are nominal values, which is why I am unsure if it will work properly right at the minimum VI_CM limit of the Spartan-6 PPDS specification.

 

I guess I'll just have to try some options in simulation for now, then see what the sensor engineers think.

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Highlighted
Visitor auduninder
Visitor
10,751 Views
Registered: ‎09-22-2013

Re: Use the force, Watman!

Hi!

I am working with the same issue as you are describing.

Have you solved the problem with just the FPGA, or did you have to design some extra hardware?

 

Cheers,

Audun

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Participant watman
Participant
10,714 Views
Registered: ‎05-19-2010

Re: Use the force, Watman!

Hi Audun,

 

I found that MIPI wants several thousand dollars before they will give any information about the protocol, so I am no longer using Omnivision image sensors.

 

Since then I am using Aptina sensors, which have a standard LVDS output that works nicely with FPGAs (and the protocol is given in the datasheet).

 

Daniel

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Visitor auduninder
Visitor
10,686 Views
Registered: ‎09-22-2013

Re: Use the force, Watman!

Thanks for the reply.

I got drafts of the specifications just by googling it.

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Newbie mehhey
Newbie
10,430 Views
Registered: ‎11-27-2013

Re: IO standard compatible with SLVS-200 on Spartan-6

Hi friends,

I want to know if there is any D-PHY IC for MIPI that I can connect to My FPGA.

I am working on a project that I deal with an ARM microcontroller and I want

to use the H264 module of microcontroller. the microcontroller is designed to get

the input video from camera via csi 2 protocol, but I want to feed a VGA or DVI signal to it.

So it sounds that I need a circuit for converting the video from DVI to MIPI. Then I deciede 

to implement the convertor on a FPGA.

The DVI part is easy to handle but I don't know how I  can emulate the MIPI behavior. After 

a  search in the internet and datasheets, I found that for implementing MIPI

 I need a PHY layer. It sounds that the information regarded this protocol is available

just to MIPI alliances and there is nothing worth over internet.

I want to know that if there is any D-PHY module exist as a stand alone module for connecting

to FPGA.

 

I was wondering if you could help me ?

Regards

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Newbie rbinns
Newbie
10,072 Views
Registered: ‎02-19-2014

Re: IO standard compatible with SLVS-200 on Spartan-6

Check these out: http://www.meticom.com/page2/Products.html

 

LVDS-to-MIPI bridges specifically designed for FPGAs.

 

Ryan

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Xilinx Employee
Xilinx Employee
2,435 Views
Registered: ‎08-01-2012

Re: Use the force, Watman!

SLVS promises higher speed differential signal at rates of 1.2Gbps - 1.35Gbps over short distances (20cm)
 
As per mybest knowledge there is no support for interfacing to SLVS with Spartan-6. The LVDS in SPartan-6 does not support that much speeds
 
I think you can try Kintex-7 LVDS for interfacing SLVS
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