Arithmetic summation (addition) on Fast DSP ADAU1787
Dear Sir,
In order to make some optimized filtering, I need to implement parrallel filtering on the FastDSP. I have tried to implement 2 basic biquad in // and sum their contribution. Surprisingly, I cannot find a basic arythmetic summation (as we can get in SigmaDSP). I have tried to use the mix unit instead but the simulation (stimulus + probe) does not give any result so I cannot check if this is working and if it provides the expected Transfer Fuction I am looking for.
I did the same with SigmaDSP and it work well.
Could you please let me know how I can do it on the FastDSP. I have attached the project as a support below.
Thanks for your answer in advance.
ADAU1787
Integrated/Special Purpose A/D Converters
Audio CODECs
Hello Bernard,
The Stimulus and Probe features are designed only for EQ curves and it is all calculated in the PC using the filter coefficients in the SigmaStudio object. You do not even have to have a DSP connected. So it does not look at what is going on in the DSP and does not look at any other objects other than filters. It also does not work for filters that calculate the coefficient in the DSP.
You should be using meters and oscillators to look at the level of the audio in the DSP. You are correct to use the mixer for summing. That would be the way to do it.
Dave T
Dear Dave,
Thansk for your answer. Yes indeed, that is what I have experienced the day before yesterday : the simulation does not work but the FastDSP is doing the job anyway. The problem is that the mixer is probably taking more ressources that a conventionnal summation. As result, after 4 biquads set in //, the FastDSP set at Fs=48kHz is no longer taking into account the additional biquads we can put in //. Is there any possibility to address a filter with14 biquads in //? With the SigmaDSP on the contrary, this is working fine with 14 biquads in // and a arythmetic summation.
Thanks for your answer in advance.
Warm regards
Bernard
Hi Bernard,
The Stimulus support is limited to EQ/Filter cells as Dave pointed out in previous reply.
The Mixer cell for FDSP will use only one instruction per channel independent of number of inputs and is recommended to be used for arithmetic sum. We do not have arithmetic sum cell available in SStudio currently similar to SDSP yet. For summing the two signals as shown in your schematic, the Mixer Cell as connected should work.
The FDSP sample rate can be set by right clicking the FDSP input cell. At 384K sample rate the FDSP can take 64 instructions and @768K it would be 32 instructions. If not explicitly set, the FDSP will use the default rate set at the top in SStudio schematic . Make sure the sources coming to FDSP are also set at the same rate else your filters may not work correctly.
If you can send your project to me, I can help debug the issue on why FDSP is not accepting more bi-quads. The other settings might be causing this issue. If ok, please send your SStudio project to rajeev.morajkar@analog.com.
Regards
Rajeev
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