[Dspforum] EDMA Questions

[Alan Ding]

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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>>
>>
>
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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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