Just to put a little button on things...
I can't look at any code here, but changing the Offset to 0 might have some side effects. If you have a tight reading loop, reading 1 sample offset by 0 from Most Recent will make DAQmx Read *wait* for up to 1/10 sec for the *next* 10 Hz sample to arrive.
The apparent *intended* behavior was to read 1 sample offset by -1 from Most Recent. After startup, this would *never* need to wait but would always immediately return the most recent *past* sample that has already arrived.
I'm educated guessing that your error happened at 10 Hz but not at 25 kHz because the first DAQmx Read is done immediately after starting the task. With a 10 Hz rate the first sample may not yet have arrived while with a 25 kHz rate it does.
So another way to restore the original behavior that returns *past* samples without erroring is to add a 1 sample DAQmx Read after starting the task, but *before* setting the Offset to -1. You can maybe discard this data, but this will at least guarantee that there will already be at least 1 sample in the buffer before you ever get to your regular reading loop.
-Kevin P
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