Implementation of Cordic Algorithm for FPGA. Based Computers Using Verilog. pani1, ju, a3. If you’ve never worked with a CORDIC algorithm before, the .. Software programmers like to look at for and while loops in Verilog and think of. 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.
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This can become very tricky, especially with negative numbers and the signed representation. Here is my code to compute sine and cosine of the input angle using cordic algorithm:. One important feature of the convertor is that it handles the details of signed and unsigned representations automatically. Hate it when I get this sort of incomplete error message.
The command shown is for the open-source Cver simulator. Sign up using Facebook. Clearly we will want to verify that the Verilog output from the convertor is correct. Site powered by Hakyll.
The page for rotation on Wikipedia tells us that it is equivalent to left-multiplying by a particular matrix: First of all, note in the Verilog output that the convertor infers which variables have to be declared as signed.
The beginner needs to understand that this is not the definition of a memory, although it might look very similar to a block RAM definition.
Email Required, algorihm never shown. Doing so, though, requires the CORDIC angles, which verilg needed to calculate based upon the desired precision of the output.
This can all be done with simple integer math—no multiplies or divides are required. You can find more information about the convertible subset in the MyHDL manual.
This code is for the first quadrant, but is easily extended to the full circle by first doing a coarse rotation. The number of stages and the number of bits in each stage can both be defined based upon arguments to the core generator program.
It loads a vpi module that defines the interface between the MyHDL simulator and the Verilog simulator. However, my current simulator Cver tells me that it is.
Ok will try and get back. We need five registers: The actual computation is done by the processor generator.
The Verilog output is as follows:. Hence we are rotating xv and yv in a counter-clockwise direction, while the remaining phase angle will decrease in what will look like a clock-wise direction.
Both the sine and the cosine of the input angle will be computed. The floating point numbers are represented as integers by scaling them up with a factor corresponding to the number of cogdic after the point.
This is what we are going to try to do: This mode seeks to reduce the angle. From here you can see that this is most definitely a rotation matrix with an amplitude increase associated with it. One would therefore expect a similar feature in other HDLs.
The implementation We will assume that all numbers are stored as bit fixed-point numbers, verrilog the radix point between the second-most-significant and third-most-significant bits. It uses the most amount of LUTS. Maybe I am not following the algorithm apgorithm. In that case just drop it from the port list.
Cordic-based Sine Computer
This is what we are going to try to build today. The interface of the module looks as follows: For now, remember that the global CE strategy requires that nothing changes unless a CE line is true.
We start by doing the Verilog conversion itself first. 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.
I believe it’s quite clear what this is supposed to do. That strategy requires that for every strobe input, the output associated with that input also needs to have a high strobe output.
It seems obvious that a type that unifies the integer and the bit vector views should be very useful for hardware design. To set up a co-simulation, we need to create a Cosimulation object for the Verilog design.
Using a CORDIC to calculate sines and cosines in an FPGA
To implement the design, we will use the Cordic algorithm, a very popular algorithm to compute trigonometric functions in hardware.
For example, consider how the look-up table of elementary arctangents is set up in the SineComputer design:. In this way, the rotating vector can be directed to converge on a particular result vector.
This means that only the source code of generator functions is converted. These rotation matrices can be strung together to accomplish many digital logic purposes. Such a core generator will be our approach here. The two states that we will use are 0an idle state, and 1a state indicating computation is occurring. That suggest to me it is an output. The resulting transform, Tis shown below: For our purposes, it can be shown that.
The next step is to rotate the xv and yv values through the remaining phase angle, ph. When writing synthesizable code, a MyHDL designer can use a high-level view for integer operations by using the intbv type, and rely on the underlying two’s complement representation to do the right thing automatically. The Cosimulation object is then constructed with the command as its first parameter, followed by a number of keyword arguments.