[Dspforum] EDMA Questions

[Joseph Haber]

I would propose that you would interdigitate after the data is loaded. You
need to load the data through the CPU to perform the short to float
conversion anyways.

It would be possible to change the DUM (destination update mode) and the IDX
to skip a 32 bit word each time.

Joseph

On Tue, Nov 3, 2009 at 2:00 PM, Alan Ding <alan33d at gmail.com> wrote:

> But if we "interdigitate" with zeros, after the buffer is filled with
> samples, aren't we going to lose data?
>
> Is there  a way to setup the IDX field to put sample elements in every
> other buffer index?
>
> On Tue, Nov 3, 2009 at 7:50 AM, Joseph Haber <josephhaber at gmail.com>wrote:
>
>> 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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>>> Dspforum at echelonembedded.com
>>> http://echelonembedded.com/mailman/listinfo/dspforum_echelonembedded.com
>>>
>>>
>>
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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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> Dspforum at echelonembedded.com
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