[Dspforum] dspF_sp_biquad

[Doug Wenstrand]

Some were having trouble with the DSPLib biquad function going off into
space.  Though finding this sort of thing is sometimes part of "the fun" of
using other people's  libraries; the documentation completely neglects to
mention this, so I think its only fair for us to help out.

The biquad function makes an assumption that nx is a multiple of 3!!!!

You could figure this out in one of two slightly obscure ways.

1) I ran in the debugger with a small value for nx.  I noted that the loop
counter was getting subttracted by 3 each time, and then went right through
0 and kept right on going forever.
and/or
2) the source for the DSPLib is provided with the library itself, and often
the assembly is better documented than the programmer's reference! (It
correctly describes the real restrictions)


Anyway, calling this function with nx not a mult of 3 will cause it to go
out into space.  Its really sad that something this important isn't in the
programmer's reference.....

Doug
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