Synopsis

This repository holds a CORDIC digital design written in VHDL. which can be used e.g. for integration in FPGA-based SOCs.

Description

CORDIC is the acronym for COordinate Rotation DIgital Computer and allows a hardware efficient calculation of various functions like - atan, sin, cos - atanh, sinh, cosh, - division, multiplication. Hardware efficient means, that only shifting, additions and subtractions in combination with table-lookup is required. This makes it suitable for a realization in digital hardware. Good introductions can be found in [1][2][3][5].

The following six CORDIC modes are supported:

• trigonometric rotation
• trigonometric vectoring
• linear rotation
• linear vectoring
• hyperbolic rotation
• hyperbolic vectoring

Furthermore, the CORDIC algorithm is implemented for iterative processing which means, that the IP-core is started with a set of input data and after a specific amount of clock cycles, the result is available. No parallel data can be processed.

In addition to an IP-core written in VHDL, a bit-accurate C-model is provided. This C-model can be compiled as mex for a usage with Octave or Matlab. Therefore, this C-model allows a bit-accurate analysis of the CORDIC performance on a higher level.

For a more detailed documentation, see ./doc/documentation.pdf

Status

• C-model implementation is done
• RTL model implementation is done
• RTL model is verified against C-model
• Wishbone-bus wrapper is added
• Included into a small SoC, tested on a spartan-3 FPGA
• Testing within an SOC is done (see ./test_sys)

Next-Steps / Open Points

• Circuit optimizations
• Numerical optimizations

Files and folders:

• ./c_octave contains a bit-accurate C-implementation of the YAC. This C-implementation is used for analyzing the performance and to generate RTL testbench stimulus (cordic_iterative_test.m). The file cordic_iterative_code.m is used to create some VHDL/C-code automatically.
• ./rtl/vhdl Contains the VHDL implementation files
• ./doc Will contain a detailed documentation in future.
• ./test_sys Contains a test system to test the YAC on a spartan-3an board

References

• [1] Andraka, Ray; A survey of CORDIC algorithms for FPGA based computers, 1989
• [2] Hu, Yu Hen; CORDIC-Based VLSI Architectures for Digital Signal Processing, 1992
• [3] CORDIC on wikibook: http://en.wikibooks.org/wiki/Digital_Circuits/CORDIC
• [4] CORDIC on wikipedia:http://en.wikipedia.org/wiki/CORDIC
• [5] David, Herbert; Meyr, Heinricht; CORDIC Algorithms and Architectures http://www.eecs.berkeley.edu/newton/Classes/EE290sp99/lectures/ee290aSp996_1/cordic_chap24.pdf

License

                   Copyright Notice                                 

  This file is part of YAC - Yet Another CORDIC Core                
  Copyright (c) 2014, Author(s), All rights reserved.               

  YAC is free software; you can redistribute it and/or              
  modify it under the terms of the GNU Lesser General Public        
  License as published by the Free Software Foundation; either      
  version 3.0 of the License, or (at your option) any later version.

  YAC is distributed in the hope that it will be useful,            
  but WITHOUT ANY WARRANTY; without even the implied warranty of    
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU 
  Lesser General Public License for more details.                   

  You should have received a copy of the GNU Lesser General Public  
  License along with this library. If not, download it from         
  http://www.gnu.org/licenses/lgpl                                  


         Author(s):  Christian Haettich        
         Email       feddischson@gmail.com