[alsa-devel] McBSP in TDM for audio codec

Peter Ujfalusi peter.ujfalusi at ti.com
Fri Jun 15 08:34:48 CEST 2012


On 06/06/2012 04:56 AM, learnom learnom wrote:

> I want to control these channel0, 1, 2, 3 independently.
> For example, lets say,
> 1) If I want to transmit the data in channel 1 only, i want to see the
> channel0 null, channel1 with data, channel 2 null, channel 3 null.
> 2)I want to transmit data at the same time, channel 1 (data) , channel2
> (Data), channel3 data, channel(data).
> Can you please let me know how to recognize that the user is sending from
> which channel, and how to setup for these two scenarios.

User space need to make sure that it is placing the data to the correct
channel. The McBSP/sDMA just see a stream of data in a memory.
McBSP do have TDM mode where you can have limited control over how the
channels are handled, but it still handle the data as stream and you can only
tell which slot it should use and which one to ignore. This TDM programming
mode is not implemented since we did not needed it so far and without a codec
it is kind of hard to test it (well, with a scope the channels can bee
observed but that would be all).


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