Re: spartan 3a starter kit rotary encoder

scienceofficer · ‎10-21-2010

I have a spartan 3a evaluation kit and 3a starter board. I was thinking of using the evaluation kit as a standalone squarewave generator similiar to the 'frequency generator' reference design of the -3e starter board.

I would need an external lcd and rotary encoder. I downloaded the bom for the starter board but it didn't list the part number for the rotary encoder. Does anyone know it's part number or the requirements of the rotary encoder?

Also, is my project possible? Is the evaluation kit able to do the job?

thanks for any help.

gszakacs · ‎10-22-2010

I don't think the rotary switch on the 3A kit is a rotary encoder. It is more like a mouse-wheel.

You can tell when it is turning, and how much in which direction, but not its absolute position.

So if you need to remember the last frequency when the system powers down and back up,

you would have to store it in flash.

-- Gabor

scienceofficer · ‎10-22-2010

Ok. Does anyone know the part number of the mouse-wheel?

Also, is it feasible to do the project on the 'evaluation kit'?

[I only want 50 MHz out, not the full 200 MHz the 'starter kit' can do.

I would rather use a keypad as input device, but I looked into that and it seems

so complicated.

eteam00 · ‎10-22-2010

I don't have the S3a starter kit, and I haven't taken the time to open the documentation package to reverse engineer it. But you should take the time to reverse engineer it, specifically the section which interfaces (and interprets) the mouse-wheel. If you are thinking of replicating the code yourself, you should understand what it does and how it works. My guess is that the entire code routine is less than 20 lines of code.

I'm going to go out on a limb here... If the mouse-wheel is a single-axis switch, it is likely a quadrature encoded (2 SPST switches) device. These are more or less generic, you can look them up on the digikey website.

Good luck, don't be shy, and don't be afraid to ask questions. By the same token, don't just sit on your bum waiting for answers in the forum, aggressively pursue information and insight wherever and however you can. Even if you guess wrong, more often than not you've learned something in the process.

-- Bob Elkind

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scienceofficer · ‎10-22-2010

I know what you mean. I don't expect to be given everything, or I'll never learn. I'm planning on putting effort to learn while doing.

In this case, all I really need is the part number of the 'rotary encoder'. It's very similiar to one used on a ddssinewave generator project [dds-60] I saw on the web . I think now that since I looked up the info that the device repeats a sequence every 20 clicks, I can order one with that specification.

eteam00 · ‎10-22-2010

In this case, all I really need is the part number of the 'rotary encoder'. It's very similiar to one used on a ddssinewave generator project [dds-60] I saw on the web . I think now that since I looked up the info that the device repeats a sequence every 20 clicks, I can order one with that specification.

I think you're wrong on the rotary encoder. Check the Spartan 3A Starter Kit schematic. It looks like a quadrature encoder, plus center button. The FPGA interprets the quadrature signals to count up and down, replicating a rotary dial.

Are you familiar with quadrature encoding? See the "incremental rotary encoder" section in this article.

And here is a nice article on quadrature decoding for FPGAs.

Once you have this straight in your mind, your next logical step is to go shopping at the digikey.com website.

-- 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.

scienceofficer · ‎11-05-2010

Success!! I was able to transfer the project for the s3k starter board onto the evaluation kit - good job if I have to say so myself!

I bought a lcd and a incremental rotary encoder and hooked it up to the board. I was a little concerned about the lcd being driven by the 3V logic of the eval kit, but no problem.

I couldn't get the 200 MHz dcm to work so I created a new one and it worked - had to created a new project to test it out.

I was worried the eval bd could creat a 200 MHz clock, but the user guide said it can generate a 240 MHz signal.

Now I have to modify the software to start at a lower frequency [now it's 100 MHz]- can't even see that high of a digital signal with my 30 MHz analog scope!

Anyway, now I have to put everything in a box and I'll have a nice frequency generator.