Filters of 18 bits with ADC Delta-Sigma in differential mode. - Cypress.com Forums http://www.cypress.com/? Re: Filters of 18 bits with ADC Delta-Sigma in differential mode. http://www.cypress.com/?rID=74075  Hooked up a voltage source and swept the range.  Everything looks good.  Thanks for the help.

I would recommend an app note for this for others who may travel down this path.  

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Mon, 07 Jan 2013 16:32:00 -0600
Re: Filters of 18 bits with ADC Delta-Sigma in differential mode. http://www.cypress.com/?rID=74074  I know them by heart.

I think I may have figured it out actually.  I found an app note that was partially helpful:  EP58353.  

So a brief explaination of the crucial details:

I have  the following registers settings on the DFB (This was the tricky part for me):  

Filter_COHER_REG = 0x55;

Filter_DALIGN_REG = 0x0F;

I have two DMA's, one to transfer from ADC to DFB, and on to transfer from DFB to SRAM.  Here are the configs and addresses from the two.
 
ADC to Filter:
 
    CyDmaTdSetConfiguration(DMA_DelSig_TD[0], 2, DMA_DelSig_TD[0],0);
    CyDmaTdSetAddress(DMA_DelSig_TD[0], LO16((uint32)ADC_DelSig_DEC_SAMP_PTR), LO16((uint32)Filter_STAGEA_PTR));
 
Filter to SRAM:
 
    CyDmaTdSetConfiguration(DMA_Filter_TD[0], 2, DMA_Filter_TD[0],TD_INC_DST_ADR);
       CyDmaTdSetAddress(DMA_Filter_TD[0], LO16((uint32)Filter_HOLDA_PTR), LO16((uint32)Filter_Output));
 
Like I said, it appears to be working now.  I'll need to spend some more time with it to be sure.
 
I'm a little concerned about the output of the ADC being in 2's complement form and the DFB not handling that.  I have to check to see what the Filter puts out when a negative value comes from the ADC.
 
 
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Mon, 07 Jan 2013 15:09:02 -0600
Re: Filters of 18 bits with ADC Delta-Sigma in differential mode. http://www.cypress.com/?rID=74069 You have seen these ?

http://www.cypress.com/?rID=37793

http://www.cypress.com/?rID=44335

Regards, Dana.

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Mon, 07 Jan 2013 13:32:45 -0600
Re: Filters of 18 bits with ADC Delta-Sigma in differential mode. http://www.cypress.com/?rID=74068 Bumping this post.  I have a similar issue I'm working on.

I'm trying to get the following chain to work.  ADC_DelSig(16bit differential)-->(dma)--->DFB_LowPass--->(dma)--->SRAM.

It's driving me insane trying to figure it out.  Any examples or pointers would be greatly appreciated.  

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Mon, 07 Jan 2013 12:12:38 -0600