Sergio,
Refer to this GUI to calculate coefficients: http://www.ti.com/tool/coefficient-calc. Remember to set the bit resolution to 24 in the Coef panel.
From a high level it seems that you are configuring the coefficients correctly: since you are working in non-adaptive mode, then you write the coefficients before ADC is powered. Details are here: http://www.ti.com/lit/pdf/slaa425 and http://www.ti.com/lit/pdf/slaa404. Just make sure ADCs are truly powered off.
However, because you are setting all other filters' N0 to 0x000000, you should have no audio at all! If you want to bypass a biquad, you should write 0x7FFFFF to N0 and set N1-D2 as 0x000000.
Regards,
J-
