HDLcoder ignores coder.const

I'm tryint to compile some code into HDL. There are weights used in digital filter which I want to precompute at the compile time.

The way I did this is

persistent c  buf tout pfb_weights;
if isempty(c)
    ...
    pfb_weights = coder.const(get_pfb_weights(settings_Nfft,settings_Ntaps));
end

The reason I think it is not working is that the coding report says:

• It lists sin function under Toolbox Function Usage: Supported List. Sin function is only used in get_pfb_weights function
• It lists coder/matlabcoder under Toolbox Function Usage: Unsupported List
• If I attempt fixedpoint conversion it complains that function "double" inside get_pfb_weights is not suitable for fixed point conversion and wouldn't proceed.

How do we fix this?

Answer 1

[David Fink]

By making the call to get_pfb_weights opaque to code generation (so fixed-point conversion won't try to process it), you can call it extrinsically (in MATLAB), at compile-time, via coder.const and coder.extrinsic.

See the coder.extrinsic documentation for a coder.const example.

Answer 2

[Kiran Kintali]

You can find examples of HDL Coder friendly designs with coder.load and coder.const in the attachment.