AIC3263 CIC control register problems (ADC very loud noise or silent randomly)

Tomasz Motylewski

Other Parts Discussed in Thread: PUREPATHSTUDIO

I an using miniDSP mode with simply transfer of data from ADC + serial audio data => to DAC (digital mixing of analog inputs with digital data from CPU)

This had beed very unstable, sometimes I had a lot of full power noise from ADC, sometimes silence. I am switching ADC and DAC on/off to save the power.

GDE PurePathStudio has generated the configuratioon with B100_P0_R50 register value of 0xa4, that means 0x80 FIFO not bypassed, 0x20 CIC auto normalization enabled, decimation factor 4.

The above problems dissapeared when I have used 0xe4 instead, theat means enabled bit 0x40 "auto clear of the read and write pointer of the CIC FIFO at the start of the frame".

Could you please tell me in depth what the bits D7, D6, D5 really do and more important, WHEN TO USE THEM ?

Also, when to use D4 bit of B100_P0_R57 ?

How does it apply to the secondary CIC2 B100_P0_R60 D6 ?

over 9 years ago

0 Luis Fernando Rodriguez S. over 9 years ago

TI__Guru* 84915 points

Hi, Tomasz,

I will take a look at this and I will answer as soon as possible.

Best regards,
Luis Fernando Rodríguez S.

0 Luis Fernando Rodriguez S. over 9 years ago in reply to Luis Fernando Rodriguez S.

TI__Guru* 84915 points

Hi, Tomasz,

The registers bits that you mentioned are related with the CIC filters. Particularly, these bits control the FIFO activity at the CIC filters. In order to completely understand how this FIFO activity works, I would suggest to take a look at the 2.13.1.6 Buffer Mode section.

All the pointers and even the FIFO behavior can be controlled by these registers. In your case, the miniDSP improved its activity since the pointers that determine the write/read functions are auto enabled at the start of frame. This would help to avoid any conflict in miniDSP memory location.

Best regards,
Luis Fernando Rodríguez S.

0 Tomasz Motylewski over 9 years ago in reply to Luis Fernando Rodriguez S.

Prodigy 170 points

Hi Luis,

The 2.13.1.6 Buffer Mode section is about SAR auxiliary ADC, not the audio ADC/CIC.

I thought that I had a stable miniDSP configuration with above settings, but then I noticed that DAC always swaps 2 samples resulting in "teeth-like" pattern on test sinus signal. I have written very simple PPS project demonstrating similar problem,
e2e.ti.com/.../533624

0 Luis Fernando Rodriguez S. over 9 years ago in reply to Tomasz Motylewski

TI__Guru* 84915 points

Hi, Tomasz,

I already replied in your second post. Please let me know if you have more questions or comments.

Best regards,
Luis Fernando Rodríguez S.

0 Tomasz Motylewski over 9 years ago

Prodigy 170 points

I have noticed that the bit bit B100_P0_R50 0x40 "auto clear of the read and write pointer of the CIC FIFO at the start of the frame" has a side effect of disabling antialiasing in ADC. Frequencies much higher than Fs/2 are coming in. This is reproducable on the evaluation board with AIC3263App8x4x framework. So we currently have no working solution.

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AIC3263 CIC control register problems (ADC very loud noise or silent randomly)