06-24-2016 09:49 PM
Hello,I am using Altera CORDIC for ATan2 and SinCos functions. I am applying the same test vectors to the CORDIC ATan2 and SinCos functions testbench and to the ATan2 and SinCos Matlab Models. I see about 10% of samples don’t match between CORDIC functions and Matlab outputs. For both Matlab and CORDIC I use the same S18,17 inputs for ATan2; S11,8 output for ATan2; S11,8 input for SinCos; S10,8 output for SinCos. Any idea why it happens? Thanks, Mike
06-25-2016 04:38 PM
--- Quote Start --- cordic gives approximate result and its accuracy depends on number of internal iterations(rotations). --- Quote End --- Kaz, Thanks! Could you please recommend application notes or/and user manuals I could learn more how to increase CORDIC accuracy?
06-25-2016 05:02 PM
--- Quote Start --- Kaz, Thanks! Could you please recommend application notes or/and user manuals I could learn more how to increase CORDIC accuracy? --- Quote End --- I understand you are using Altera's cordic but can't find any link to its manual. Xilinx has cordic ip and its manual at: http://www.xilinx.com/support/documentation/ip_documentation/cordic/v6_0/pg105-cordic.pdf This should give you some idea about available settings. there is also a cordic ip at opencores. It is not difficult to write your own targeting specific trigonometric function. The following pdf provides a good basis: http://www.ee.ic.ac.uk/pcheung/teaching/ee3_dsd/crdcsrvy.pdf