DFB examples using the DALIGN options

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SuMa_296631
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Level 5
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I have a 12-bit ADC that I want to filter using a DFB and then (for test purposes) output to an 8-bit VDAC. (I want the 12-bit ADC to get a reasonable resolution on my signal and I don't really want to drop down to 8-bits. The VDAC output is only for initial testing purposes as I really want the output of the DFB so I can output it on an OLED display so the more bits the better

   

All of the examples I can find use an 8-bit ADC when using DBA to the DFB. (I've looked in the examples projects, on the Cypress web side and used Google.)

   

I must admit that I do find the DFB datasheet a little confusing at the moment - perhaps when I understand what it is actually saying then it might make sense.

   

I can use the CPU to read the ADC and write to the DFB and similarly read the DFB holding register and write a shifted value to the VDAC but I really want to know how to set up the DFB to accept a 12-bit value via DMA into the staging registers.

   

PSOC 5LP on an -059 kit.

   

Thanks

   

Susan

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Anonymous
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I had an example project for 16 and 24 bit filter. You could use the 16 bit filter example and modify it accordingly.

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SuMa_296631
Level 5
Level 5
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Thanks Keerthi - From that I was probably not that far out (still don't know why the DFB only ever output a value of 0x01!) but it is good to see a 'real' example that I can work from.

   

Susan

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Anonymous
Not applicable

All you need to take care is coherency, data align bits and read/write pointers. Data align is required if you are doing 2 byte transfer. 

   

Page 24, 25, 26, 27 of the filter component datasheet talks about this.

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SuMa_296631
Level 5
Level 5
50 replies posted 25 replies posted 10 replies posted

The DMA transfer works nicely now - thanks Keerthi.

   

Susan

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