Siddharth

Board for project

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I am a student. Me and my friends are working on spartan 6 fpga based digital circuit for torque vectoring. I wish to use the fpga for PWM motor control (2 BLDC motors) and to make some calculations for which variables will be fed using hall effect sensors. Can you suggest me a board for the same. I am considering 

1.Nexys 3 Spartan-6 FPGA Trainer Board 

2.Atlys Spartan-6 FPGA Trainer Board 

 

Ps: if you think that some other board can help us then please do tell. We can consider other FPGA's too if Spartan 6 is not available.

 

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Hi Siddharth,

I apologize for not getting back to you sooner. Either of the boards you listed will work nicely for your application, but any FPGA will be able to accomplish what you are hoping to do. The biggest thing that I would recommend would be to use either a PmodHB3 or a PmodHB5; both of these modules nicely collect all of your signals (motor direction, motor enable, and two feedback lines for hall effect sensors) into one board that you can plug into a Pmod port and allow you to attach your external motor power to the module (presuming your motors do not run at too high of a voltage).

There is a project available on the Nexys 3 Resource Center that uses the PmodHB5 to drive DC motors that you can easily modify for other boards or newer software programs (such as Vivado for a 7-series based FPGA over ISE for a deprecated 6-series based FPGA).

Let me know if you have any more questions.

Thanks,
JColvin

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Hello Colvin

Thanks for the reply. But I have few queries.

1. Actually we wish to use this for torque vectoring in a vehicle and FPGA are really fast and high performance. That's why we are going for FPGA. Do you think we don't need one? because what we wish to have is response within a microsecond. ( and if possible a few nanoseconds)

2. We are currently making a simple prototype but we look further to expand this as in, the inputs shall go up to 4 or 5. 

3. Also, since we wish to use it in a vehicle, the motor will operate at 60-70 volts. 

Also someone suggested me using a Cmod. I don't know if it will help?

 

Since we a student group , we would like a board that can do the job for us in both, the initial prototyping stage and the final stage. Please could you suggest a board for the same.

Best 

Siddharth

 

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Siddarth,

The reason I suggested a CMod was because your requirements were so vague.  Your current requirements are ... less so.

You wish to do some (unnamed) calculation in less than a microsecond, and then to output the result via a PWM type of output.  Further, you wish to do this with a Spartan 6.

From my experience, a Spartan 6 can do one full 32-bit operation (with carry) per cycle at a 12.5 ns clock.  (Roughly--a 32-bit multiply takes at least two clocks, and these are rough numbers anyway.)  These operations can be made massively parallel (welcome to FPGAs!), but the carries don't parallelize very well.  How complicated is your operation?  Figure at least two clocks to read your input (assuming it's digital), and so forth from there.  Be aware, though, that PWM is inherently slow, especially at any high "resolution".  While the FPGA can recalculate what you need every clock, it may take several clock cycles for the PWM answer to be sufficiently useful for you.

To really know what FPGA you need, how big is big enough, and so forth, I would recommend building a design ahead of time in ISE (since you are planning on using the Spartan 6), and then experimenting to see what chips your design will fit within.

As for what board, look at the peripherals on the board.  The two biggest distinguishing characteristics between Xilinx's FPGA boards are the FPGA on the board and the peripherals attached.  Find the board with the peripherals you will need.  If all you need is digital I/O and a PWM out with minimal logic in between, then a CMod might work for you.  Indeed, if you are looking at a high digital I/O count, you might wish to look hard at the CMod.  However, if you need much more logic than a Spartan 6 LX4 can offer, then the answer becomes more complex to figure out.  (The LX4 is the bottom of the line Spartan 6 ...)

As for the 60-70 Volts, you'll need to work the voltage translation issues carefully.  All of the logic I've been using has been at 3V. 

Yours,

Dan

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