Implementation of Cordic Algorithm for FPGA. Based Computers Using Verilog. pani1, ju, a3. The CORDIC rotator seeks to reduce the angle to zero by rotating the vector. To compute . See the description of the CORDIC algorithm for details. */ module. Tags: verilog code for cordic algorithm verilog code for vector verilog code for .. specific device designations, other words log Abstract.. code in the example.

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In addition to the Verilog code for the design itself, it also generates a Verilog test bench stub that defines an interface between the Verilog design and a Cosimulation object. You clear the angle during a reset just like cos, sin, count etc.

### Computing sin & cos in hardware with synthesisable Verilog

For high-level, algorithmic work, this is much easier. Our task here will be to calculate that gain.

verjlog The core will operate in one of two modes: It basically calculates the product of all of the gains of the various stages in our algorithm. Of course, we still need to make sure that the convertor gets it right, which is hard enough. I updated the code as output [ See Terms of Use.

## Cordic-based Sine Computer

Unable to figure it out, I am beating my head. The floating point numbers are represented as integers. Software programmers like to look at for and while loops in Verilog and think of them like their for and while counterparts in software.

Note that we have been talking about the convertible vwrilog, and not about the “synthesizable subset”. The Cordic algorithm is an iterative algorithm based on vector rotations over elementary angles.

The first step in building this rotation, though, is to massage the problem so that the rotation desired is less than 45 degrees. Rotating into range The first step in building this rotation, though, is to massage the problem so that the rotation desired is less than 45 degrees.

I believe that writing the code in a natural, high-level way in MyHDL, and letting the convertor take care of the low-level representation issues, is a better option. That strategy requires that for every strobe input, the output associated with that input also needs to have a high strobe output. Let me get algroithm straight: Is there any way to get around this error?

Note that outside the generator function, we calculate some data such as the X0 constant, and the look-up table of elementary arctangents, represented by the angles tuple.

## Using a CORDIC to calculate sines and cosines in an FPGA

A simple two-dimensional rotation matrix is given by:. While the data width can ostensibly be adjusted, there are a fixed number of internal arc-tangent results, each created with a fixed width and a fixed value.

The pleasant consequence is that the restrictions of the “convertible subset” apply only to the code inside generator functions, not to any code outside them. For pipelined options, this is the number of stages. Going to a higher number of bits would allow more iterations thus improving accuracy. T is also something that is easy to calculate within an FPGA. From here you can see that this is most definitely a rotation matrix with an amplitude increase associated with it.

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Further, as you may have guessed from Fig 1 above, we can apply a cerilog rotation going in the opposite direction:. To see this, first calculate the angles of the vectors in Fig 1 above:.

Verjlog more iterations or higher precision calculations are desired then a new arctan table will need to be computed. For veeilog information and background on the algorithm itself, please consult other sources, such as this paper by Ray Andraka. Here is the code:. Then also calculate and normalize by their their lengths. We veripog assume that all numbers are stored as bit fixed-point numbers, with the radix point between the second-most-significant and third-most-significant bits.

So you’re saying I remove it from the port and leave it reg as it is? That’s why I defined it as reg. HDL loops, however, cordc nothing like software loops.

For example, consider the instantiation of the design under test in the test bench:. This can become very tricky, especially with negative numbers and the signed representation. On the other hand, we can access their two’s complement representation as a bit vector, for example for slicing or right-shifting. One would therefore expect a similar feature in other HDLs. A signal named init is instantiated to load the input values.

The beginner needs to understand that this algorihhm not the definition of a memory, although it might look very similar to a block RAM definition. This define determines the number of bits used to represent the angle. Outside generator functions, you can use Python’s full power to describe designs. Here is my code to compute sine and cosine of the input angle using cordic algorithm: The described behavior is a unique feature of the MyHDL design flow.

In this way, the rotating vector can be directed to converge on a particular result vector. Obviously, MyHDL code intended for synthesis also has to take synthesis-related restrictions into account.

Inline mathematics generated on MathJax. It loads a vpi module that defines the interface between the MyHDL simulator and the Verilog simulator.