[Dspforum] EDMA Questions

[Joseph Haber]

All,

One common way to handle this is to have a for loop in the processing that
occurs after the EDMA for a ping or pong buffer is done, prior to the FFT.
That would iterate through the loop, select one channel, perform the
short-to-float conversion, and interdigitate with zeros.

Joseph

On Tue, Nov 3, 2009 at 1:07 AM, Alan Ding <alan33d at gmail.com> wrote:

> - ping and pong buffers are of size COMPLEX*FFTLEN. Does that mean that
> they are automatically filled with complex zeros or do we have to do that?
>
> I think we have to do that... I'm still trying to figure out how this
> element index offset thing work.   Since we are DMA'ing 32-bit ints that are
> L and R channels into a float buffer, how do we extract just the left
> channel?
>
>
>
> - i have issues finding/understanding RLD register. What is it used for?
>
> From spru234.pdf:
>
> "EDMA Channel Count Reload/Link Address Parameter (RLD)
> The EDMA channel count reload/link address parameter (RLD) in the EDMA
> parameter entries specifies the value used to reload the element count
> field
> and the link address. The RLD is shown in Figure 2-18 and described in
> Table 2-25.
> The 16-bit unsigned element count reload (ELERLD) value reloads the
> element count (ELECNT) field in the EDMA channel transfer count parameter
> (CNT), once the last element in a frame is transferred. ELERLD is used only
> for a 1D element sync (FS = 0) transfer, since the EDMA has to keep track
> of
> the next element address using the element count. This is necessary for
> multiframe
> EDMA transfers, where frame count value is greater than 0. See
> section 1.7 for more details.
> The EDMA controller provides a mechanism to link EDMA transfers. This is
> analogous to the autoinitialization feature in the DMA. When LINK = 1 in
> the
> EDMA channel options parameter (OPT), the 16-bit link address (LINK)
> specifies the lower 16-bit address in the parameter RAM where the EDMA
> loads/reloads the parameters of the next event in the chain. Since the
> entire
> EDMA parameter RAM is located in the 01A0 xxxxh area, only the lower 16-bit
> address is required.
> The reload parameters are specified in the address range 01A0 0180h to
> 01A0 07F7h. You must ensure that the link address is on a 24-byte boundary,
> and that the operation is undefined if this rule is violated (see section
> 1.9). In
> addition to the reload parameter space, the entry of any unused EDMA
> channel can also be used for linking. The EDMA can always have up to 85
> programmed entries, regardless of the number of channels actually used."
>
>
> On Mon, Nov 2, 2009 at 11:07 PM, Nenad Uzunovic <nenad at roboticresearch.com
> > wrote:
>
>> Hi there,
>>
>> I have a few questions about the EDMA lab.
>>
>> - ping and pong buffers are of size COMPLEX*FFTLEN. Does that mean that
>> they are automatically filled with complex zeros or do we have to do that?
>>
>> - i have issues finding/understanding RLD register. What is it used for?
>>
>> Thanks,
>> Nenad
>>
>>
>>
>>
>>
>>
>>
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>>
>
>
>
> --
> -------------------------------------------------------
> Alan Ding
> Master of Sci, Electrical Engineering
> Johns Hopkins University
>
> Email: alan33d at gmail.com
> Contact #: 4844593290
>
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>
>
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