Hello,
On Wednesday 03 March 2010 17:01:39 Ujfalusi Peter (Nokia-D/Tampere) wrote:
On Wednesday 03 March 2010 16:18:42 ext Jarkko Nikula wrote:
On Wed, 3 Mar 2010 12:02:48 +0200
Peter Ujfalusi peter.ujfalusi@nokia.com wrote:
The command for test: aplay -fdat -d 1 /dev/urandom
I recommend to use /dev/zero instead since urandom takes CPU time.
[ 96.290924] XBUFFSTAT: 0 [ 96.293487] XBUFFSTAT: 0 [ 96.296020] XBUFFSTAT: 0 [ 96.299774] XBUFFSTAT: 1
So the buffer is kept full in element mode, as it is expected.
I was expecting to see more variations. IRCC, the DMA in OMAP is doing transfers over the memory bus using some small bursts but I'm not completely sure. I'm thinking if that could explain the Eero's and Liam's observations?
I kind of expecting similar result (this). In element mode the threshold value is 0 (1 word). So if one word is free in McBSP buffer, than it will assert the DMA request line, and the DMA will write one word to McBSP. So in theory the buffer must be kept full in this mode, with quite minimal variation. But I might be wrong on this...
Well, to be precise, I expected that the XBUFFSTAT would have been 1 most of the time, and not 0. But in stereo we are still within one sample accuracy, so I think this is OK.