FIR limited to 700
I am using an ADAU1451 integrated in an audio amplifier (Beocreate) and develop with SigmaStudio.
The target is simply to use a 2k FIR.
- Even if the FIR limit is 800, I cannot declare a table longer than 700. The compiler is OK but with a 800 FIR, the amplifier generates a sound as soon as the configuration is loaded and this sound is independent from the volume.
- I have done many simulations while splitting the FIR, using delay and adder to generate the final FIR but it seems that the 700 taps limit is still present. With any possible architecture >700, the amplifier generates a noise and is useless. This has no relation with FIR coefficients as trials with one 1.0 coefficient and 0.0 for others give the same result.
Any ideas ?
Audio Signal Processors
adau1451
fir filter
SigmaDSP Audio Processors
Hello,
The ADAU1451 doesn't have an intrinsic 800-tap FIR limit. The schematic below totaling 1920 x 2 taps compiles OK for a ADAU1451 and runs fine on a stock AD evaluation board. Yet, this is different than the Beocreate environment, so the differences may help us discern why filters larger than 700 taps won't work there:
My eval board's sample rate is hardwired at 48K. If the Beocreate runs at 96K, you have only half the instructions available. At 192K, only a quarter can be used. This is because the DSP has to complete its instruction load for each sample before the next one arrives. The faster the sample rate, the less time your program has to execute -- thus the less it can do.
My schematic includes only the FIR filters. Other items such as EQ which my be included in Beocreate's stock schematic take up resources, limiting what you can add.
You can troubleshoot issues like this by viewing SigmaStudio's Output Window. I suspect that your results shown there will be quite different than what I'm seeing below, for the reasons described above. See how close the various resources shown in your Output Window come to their limits. For example, Total instruction cycles must be less than 8192 at 48K sample rate, 4096 at 96K, or 2048 at 192K.
Best regards,
Bob
Please log in to reply.