Hello.
I am experimenting with the TLV320AIC3254 evaluation kit. My target goal is to produce a low power shortwave radio, where most of the processing is done by the 3254. Currently I am having trouble to understand how the ADC processing works.
I am confused about which of the processing blocks are executed on the miniDSP and which are standalone hardware modules. I think the SLAS549A should be improved to put stress on which modules are mutually exclusive with the miniDSP. For a long time I really thought many of the blocks are hardwired next to the miniDSP and I was overjoyed about it. It took me a while to find the following line in the registry table:
Page 0 / Register 61: ADC Signal Processing Block Control Register:
0 0000: The ADC miniDSP will be used for signal processing
Now I believe I got it and understand that many of the processing blocks including the decimation filters of the ADC path are done purely on the miniDSP, right?
Section 5.9 - "ADC Decimation Filtering and Signal Processing" describes processing blocks with the decimation filters A/B/C and the frequency characteristics of the A/B/C filters are given in detail. When adding an AD input block into the PPS worksheet, what decimation filter will be used?
Where are the CIC decimation filters positioned in the whole picture? I suppose they are hardware CIC filters outside the miniDSP, but the A/B/C filters are implemented using the miniDSP?
When I set the ADC preamp to +20dB, I found out that no input signal is mapped to around 1/2 of the ADC span. That means at +20dB I get a heavy DC component and 6dB lower dynamic range. I believe at +30dB preamp the DC offset was out of the ADC range. Is it normal or is there any way to tame the preamp offset?
Does the ADC AGC control the ADC preamp only? Or does it control the ADC digital volume control as well?
What is the digital volume control anyway? It says it spans from -12dB to +20dB. Is it just a multiplication inside the miniDSP? Or is it a hardware multiplier between the CIC filter and miniDSP? How does setting the digital volume control different from 0dB affect the dynamic range and noise?
Thank you for enlightment,
Vojtech