Hi Maurice-
There are several possible causes for error 42 in DAQmx Base, but based on your description it sounds like you're running into a memory allocation error. In DAQmx Base, we internally allocate acquisition buffers for AI operations. There is a requirement imposed by DAQmx Base that the buffer be composed of a single contiguous block of memory due to the architecture of the DMA engine that we use to interface with the hardware.
This allocation occurs within DAQmx Base Start Task. So, if you repeatedly allocate and release it is possible that memory may become fragmented to some point that does not allow for further contiguous allocation operations. It seems an extreme case that 40kB of contiguous memory is not available (for your 20kSample buffer), but it is possible. The fact that it eventually begins working again seems to indicate that other processes might be releasing memory "chunks" that then become available to DAQmx Base. There is no way to avoid this limitation in DAQmx Base.
Is there a reason why you need to Start and Stop repeatedly in a loop? In the past, to overcome this long-term limitation of DAQmx Base, I have suggested using a continuous analog input operation and using post-processing on the data to determine when analog trigger conditions are met. This would require you to supply the analog signal of interest to another of the AI channels and then add that channel to your scanlist.
How many iterations are you able to run before the failure occurs? How much RAM is available in your PowerPC machine? Is there significantly more available in the Intel machine? FYI- the fact that one machine is using E Series and another using M Series should not make a difference in this case.Message Edited by Tom W [DE] on 07-02-2008 10:37 AM