function/process to generate sine and cosine wave

I would like some guidline on writing a function or process to
generate a sine wave and cosine wave. I want to include this into my
library. Each time this function/process is called, I would like sine
and cosines wave generated.

Are there any functions in VHDL which would help us do so. I know
there is a function UNIFORM to generate random numbers, not sure if
there is anything available for sine and cosine.

Your comments are appreciated.


Anuja

I would like to use the CORDIC function available in math_real to
generate the sine and cosine wave. Any inputs on if this is possible
would be appreciated.

FPGA wrote:
> I would like some guidline on writing a function or process to
> generate a sine wave and cosine wave. I want to include this into my
> library. Each time this function/process is called, I would like sine
> and cosines wave generated.
> 
> Are there any functions in VHDL which would help us do so. I know
> there is a function UNIFORM to generate random numbers, not sure if
> there is anything available for sine and cosine.
> 
> Your comments are appreciated.
> 
> 
> Anuja

what frequency?
what resolution?
synthesizable or testbench?

andraka.com has a good cordic article on it among other things.

-Jeff

On Feb 6, 10:05=A0pm, Jeff Cunningham <j...@sover.net> wrote:
> FPGA wrote:
> > I would like some guidline on writing a function or process to
> > generate a sine wave and cosine wave. I want to include this into my
> > library. Each time this function/process is called, I would like sine
> > and cosines wave generated.
>
> > Are there any functions in VHDL which would help us do so. I know
> > there is a function UNIFORM to generate random numbers, not sure if
> > there is anything available for sine and cosine.
>
> > Your comments are appreciated.
>
> > Anuja
>
> what frequency?
> what resolution?
> synthesizable or testbench?
>
> andraka.com has a good cordic article on it among other things.
>
> -Jeff

has to be synthesizable. No restriction on frequency or resolution as
such.

On Feb 6, 10:05=A0pm, Jeff Cunningham <j...@sover.net> wrote:
> FPGA wrote:
> > I would like some guidline on writing a function or process to
> > generate a sine wave and cosine wave. I want to include this into my
> > library. Each time this function/process is called, I would like sine
> > and cosines wave generated.
>
> > Are there any functions in VHDL which would help us do so. I know
> > there is a function UNIFORM to generate random numbers, not sure if
> > there is anything available for sine and cosine.
>
> > Your comments are appreciated.
>
> > Anuja
>
> what frequency?
> what resolution?
> synthesizable or testbench?
>
> andraka.com has a good cordic article on it among other things.
>
> -Jeff

has to be synthesizable. No restriction on frequency or resolution.

FPGA wrote:
> I would like some guidline on writing a function or process to
> generate a sine wave and cosine wave. I want to include this into my
> library. Each time this function/process is called, I would like sine
> and cosines wave generated.
> 
> Are there any functions in VHDL which would help us do so. I know
> there is a function UNIFORM to generate random numbers, not sure if
> there is anything available for sine and cosine.
> 
> Your comments are appreciated.
> 
> 
> Anuja


Is this for a testbench or for sometihng that is going into hardware? 
If for a testbench, just use the math_real sin and cos functions, 
converting the resulting reals to the format you need to drive your 
hardware.  If it is to be synthesized into hardware, the math_real 
library isn't going to help you much, as reals don't map directly into 
synthesizable hardware.

On Feb 6, 11:42=A0pm, Ray Andraka <r...@andraka.com> wrote:
> FPGA wrote:
> > I would like some guidline on writing a function or process to
> > generate a sine wave and cosine wave. I want to include this into my
> > library. Each time this function/process is called, I would like sine
> > and cosines wave generated.
>
> > Are there any functions in VHDL which would help us do so. I know
> > there is a function UNIFORM to generate random numbers, not sure if
> > there is anything available for sine and cosine.
>
> > Your comments are appreciated.
>
>
> Is this for a testbench or for sometihng that is going into hardware?
> If for a testbench, just use the math_real sin and cos functions,
> converting the resulting reals to the format you need to drive your
> hardware. =A0If it is to be synthesized into hardware, the math_real
> library isn't going to help you much, as reals don't map directly into
> synthesizable hardware.

Using the math_real library can do for now. I have had a look at the
sin and cos functions there. I am also aware on how to conver the real
format to the format I want. I intend to generate a wave. sin and cos
in math_real would just generate a value for a particular input. How
can i generate a sine or cos waveform. I wish to make this function
parametrized as follows (not sure if this should go into a function or
process)

function sin (x: signed, bw : integer) return signed is

x: signed input with variable bit width
bw : desired bit width of output

I can convert signed to real and then use "sin" function in math_real.
I am still not sure on how I would generate a wave for each call.

Your comments would be appreciated

You need to run a count or phase accumulation to feed into the sin/cos 
function.

signal phase: real;
constant scale: real:= 2.0**bw;


for n in 0 to 10000 loop
	sig <= std_logic_vector(to_signed(integer(scale*sin(phase)),bw);
	phase <= phase + phase_increment;
	wait until clk='1';
end loop;





FPGA wrote:

> On Feb 6, 11:42 pm, Ray Andraka <r...@andraka.com> wrote:
> 
>>FPGA wrote:
>>
>>>I would like some guidline on writing a function or process to
>>>generate a sine wave and cosine wave. I want to include this into my
>>>library. Each time this function/process is called, I would like sine
>>>and cosines wave generated.
>>
>>>Are there any functions in VHDL which would help us do so. I know
>>>there is a function UNIFORM to generate random numbers, not sure if
>>>there is anything available for sine and cosine.
>>
>>>Your comments are appreciated.
>>
>>
>>Is this for a testbench or for sometihng that is going into hardware?
>>If for a testbench, just use the math_real sin and cos functions,
>>converting the resulting reals to the format you need to drive your
>>hardware.  If it is to be synthesized into hardware, the math_real
>>library isn't going to help you much, as reals don't map directly into
>>synthesizable hardware.
> 
> 
> Using the math_real library can do for now. I have had a look at the
> sin and cos functions there. I am also aware on how to conver the real
> format to the format I want. I intend to generate a wave. sin and cos
> in math_real would just generate a value for a particular input. How
> can i generate a sine or cos waveform. I wish to make this function
> parametrized as follows (not sure if this should go into a function or
> process)
> 
> function sin (x: signed, bw : integer) return signed is
> 
> x: signed input with variable bit width
> bw : desired bit width of output
> 
> I can convert signed to real and then use "sin" function in math_real.
> I am still not sure on how I would generate a wave for each call.
> 
> Your comments would be appreciated

Bresenhams algorithm provides better results with far less accumulator
bits
compared to a phase accumulator.
Also, the input parameters (M waves in N cycles) are very convenient
in many cases.


If the OP wants a sine, one option that avoids the sine computation is
an oscillator:
next_sin  <= cos*k;
next_cos <= sin*k;
The constant k determines the frequency.

Kolja Sulimma

On 7 Feb., 09:00, Ray Andraka <r...@andraka.com> wrote:
> You need to run a count or phase accumulation to feed into the sin/cos
> function.
>
> signal phase: real;
> constant scale: real:= 2.0**bw;
>
> for n in 0 to 10000 loop
>         sig <= std_logic_vector(to_signed(integer(scale*sin(phase)),bw);
>         phase <= phase + phase_increment;
>         wait until clk='1';
> end loop;

On Feb 7, 11:00=A0am, Ray Andraka <r...@andraka.com> wrote:
> You need to run a count or phase accumulation to feed into the sin/cos
> function.
>
> signal phase: real;
> constant scale: real:=3D 2.0**bw;
>
> for n in 0 to 10000 loop
> =A0 =A0 =A0 =A0 sig <=3D std_logic_vector(to_signed(integer(scale*sin(phas=
e)),bw);
> =A0 =A0 =A0 =A0 phase <=3D phase + phase_increment;
> =A0 =A0 =A0 =A0 wait until clk=3D'1';
> end loop;
>

That's good, but in math_real library sin/cos generate by Tailor
formula. And type real have very small size. All of this get not good
sin. These can give that noise of your system will grow.