[sdiy] The Owl: ARM fx pedal

[Martin Klang]

On 24 Apr 2013, at 18:43, Paul Beckmann wrote:

> Hi Terry and Martin,
> An open source effects pedal is a great idea.  We had brainstormed about this in the past and considered leveraging our Audio Weaver design tools.  We figured that about 90% of customers would want to design audio effects graphically while the other 10% might roll up their sleeves and write their own C code.

I think we want to target programmers to begin with (the 10%), then expand.
What we want to leverage is the skills and talents of all the coders who are currently doing VST plugins and other software-based solutions.

> The benchmarks listed on the hoxtonowl.com web site aren't accurate.  The Cortex-M4 has basic DSP instructions but lacks a lot of the capabilities of a traditional DSP.  A DSP can do a Biquad in 5 instructions; the Cortex-M4 takes about 13 cycles in the inner loop.  If you are open to changing processors, you might look at the M4 family from NXP.  The device runs at up to 204 MHz.

Can you elaborate on this, please?
I'm not an expert, I but I understand a biquad filter requires 5 multiply and accumulate (MAC) operations per sample.
The Cortex M4 does single-cycle MAC - see here:
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0439b/CHDDIGAC.html

Therefore I don't think our information is inaccurate, though it could be more precise. Please correct me if you think I'm wrong!

best,

Martin