- From: David Schleef <ds_at_schleef.org>
- Date: Wed, 4 Sep 2002 14:12:20 -0700
On Tue, Sep 03, 2002 at 09:16:14AM -0700, Jack Culpepper wrote: > Correct. The switch happens briefly, then things go back to normal, then it > happens again. To give you an idea of the time scale, when sampling at 4 KHz, > the problem appears about once every 15 seconds (although it's not periodic), > and lasts for maybe 50-100 samples. This is quite possibly DMA writing to the wrong part of the Comedi buffer. 0.7.65 doesn't have very good control over which regions of the buffer belong to DMA vs. belonging to the reader. Rewriting the buffer code has been one of the major developments lately, and it's taking a while to settle. You should be able to reduce the chance of seeing this problem by increasing the buffer size. You can eliminate it entirely by disabling DMA in the driver (USE_DMA in ni_pcimio.c). dave...
Received on 2002-09-04Z20:12:20