4 BASIC CONCEPTS
NOTICE
When the data are streamed via USB or Ethernet, filter rate and frame rate have
to be matched. This is important as an inappropriate sample rate may lead to
oversampling or aliasing. In the PICOSCALE GUI, potential aliasing is indicated
by a small warning sign and the frame rate can easily be adapted to the filter.
NOTICE
When SmarAct’s motion controller MCS2 is connected, the filter rate is fixed to
39.06 kHz to match the MCS2’s sample rate and thus to avoid aliasing.
4.7 Streaming aggregation
When data sources are streamed to the
PICOSCALE via USB or Ethernet, the PICOSCALE usually
bundles a certain amount of data before it sends them. This so-called aggregation decreases the
communication overhead significantly. If data are streamed with a specific frame rate, the
PICO-
SCALE
automatically uses a convenient aggregation size. This aggregation size is roughly set to
provide about 20 data packages per second. The protocol works most efficient if the aggregation
size is a power of 2, i.e.
Aggregation = 2
n
, n ∈ N
However, if an external clock is used as frame rate, the PICOSCALE cannot know the precise frame
rate and thus also an aggregation size cannot be estimated. The user has to set the desired aggre-
gation manually. In the following table please find an overview on the frame rates and respective
aggregation size the
PICOSCALE uses for direct streaming (i.e., an internal clock is used as frame
rate), which may serve as and rule-of-thumb to set the aggregation.
4.8 Network discovery protocol
The
PICOSCALE network discovery protocol enables to list all available PICOSCALEs in your local
network. Within the
PICOSCALE GUI you may then easily select the appropriate device without
typing in the IP address after every startup of the
PICOSCALE or restart of the GUI. See chapter 7
for usage of the protocol with the GUI.
27
PicoScale User Manual
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