User manual

Multi frame data acquisition
While single frame accesses are a convenient way to read multiple input signals all at
once, maximum achievable sample rate is limited due to timing limits of USB. With a
typical host system minimum time frames are between 1ms and 4ms, hence the
maximum sample rate will be about 250 up to 1.000 frames per second. Besides,
latency of most host systems cannot be guaranteed and therefore frame to frame timing
might vary. If you want to do measurements with well defined sample rates or need the
highest possible frame rate, use the multi Frame DAQ methods of CEBO-STICK.
Methods
CEBO-STICK supports four methods for multi frame data acquisition:
1. startBufferedDataAcquisition()
2. startContinuousDataAcquisition()
3. startBufferedExternalTimedDataAcquisition()
4. startContinuousExternalTimedDataAcquisition()
These four modes can be classified as two groups: the hardware timed modes (1. + 2.),
where timing is done by CEBO-STICK, and the external timed modes (3. + 4.), where
an adequate clock signal has to be provided on digital input IO-0, which has to be
configured as trigger input, then. Hardware timed modes also support a triggered mode,
where data acquisition is delayed until a valid trigger event has been detected.
Continuous data acquisition
Each group supports continuous as well as buffered data acquisition. In continuous
modes, once you start data acquisition, data is captured continuously until you stop it.
To compensate for host system timing issues, CEBO-STICK provides an onboard
buffer. Make sure to read frames as fast as possible to avoid buffer overflows.
Buffered data acquisition
With buffered modes, data is captured to onboard memory of CEBO-STICK and stops
automatically, when a given number of frames has been stored. Use these modes, if
you need a high sample rate, but your host system is not capable to sustain such high
data rates. The maximum number of samples you can capture using buffered modes is
limited by the amount of onboard memory and depends on frame size. Use
calculateMaxBufferedInputFrames() to get the maximum number of frames that fit into
CEBO-STICK Reference Manual Cesys GmbH
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