Unwanted offset attenuation in FIR filters

I basically wanted to report, that the attenuation is introduced by the FIR compiler. I didn't check the options to change this behaviour, it should be discussed in the FIR compiler manual. As I said, I don't use the tool in my designs yet. But I expect, that you can basically achieve a gain of 1.

I also didn't check the implications of using different number represenation with the FIR tool. I just told, how it should be according to usual DSP practice. Apparently, the ADC number format can be switched in your ADDA hardware, otherwise the MSB has to be inverted, most likely necessary for the DAC.