[SOLVED] Cordic ip in xilinx

Angle range according to Cordic V6.0 product guide is +/- Pi (+/- 180°). Can it be that you are reading negative cos output incorrectly?

Thanks for responding,
Iam giving input(phase) as 32 bit
For example 108 degrees after conversion 1.88496 in radians.
This input radians should be in the format of MSB 3 bit integers (2QN==>1sign+2 integer) and remaining bits as fractions
1.88496 in the above format as 32'b001111000.......
Output is 64 bit which includes both sine and cosine values each 32 bit

[63:32] for sine values and the output i got is 32'b00111101.............(1QN- MSB 2 bit integer ==> 1 sign+ 1integer )
format and remaining as fractions.
And the output is correct for this sine value i.e 0.951


[31:0] for cosine values and the output i got is 32'b11101101................(1QN-MSB 2 bit integer ==>1sign+1 integer) format and remaining bits as fractions
Here the output should be -0.309
But I am getting -1.687



Here I am using leds on fpga for verifying the output, input is given directly in the port declaration.

Can anybody help me
Did i made any mistake in reading the values?

Hi

I did not re calculate your values, but your math result of "-1.687" tells me you don't treat it right when the value is negative.

The result is a 32 bit signed integer. A standard one.
Not a "sign plus 31 bit unsigned int"

Let's go for an 8 bit example.
0 will be represented as 0b 0000 0000
1 will be represented as 0b 0000 0001
But -1 will be represented as 0b 1111 1111, (not 0b 1000 0001 as you treat it)

So in your case:
Define sin_i as "signed 32 bit int" // integer sine value of cordic result
Define cos_i as "signed 32 bit"
Define "cos" as "float"
And try this math:
sin = (float)sin_i / 2.0^30 // 30 is the count for fractional bits
cos = (float)cos_i / 2.0^30

(I'd define a structure of 2 x "int32" as 64 bit cordic result)

Klaus