User manual

Single value IO
Single value IO is the most basic form to sample an input or modify an output. The call
is synchronous, so invoking a method processes the request always immediately, which
means:
• In case of sampling: The result of the called method is the sampled value, the
method call lasts as long as sampling and data transmission from device to host
is active.
• In case of modify: The method call sends the value to the peripheral directly and
returns.
15
Single value command and response times
Min.
3,16
Typ.
3,16
Max.
3,16
Unit
Analog input
17
0,80 0,93 6,00 ms
Digital input
17
0,70 0,86 4,00 ms
Digital output
18
0,32 0,38 2,00 ms
Single frame IO
As using single value IO transfer is easy, there are also some drawbacks. For example,
if you want to read more than one analog input at a time, some overhead will occur,
reducing the maximum achievable update rate.
A better approach in this case would be to define a list of input signals to be sampled,
tell the device to sample them and then get the values with only one USB reading. With
the help of single frame IO transfers you can achieve exactly this behavior, reducing
necessary USB transfers to a minimum.
Another benefit of doing framed readings is, that host latency no longer affects timing
between sampled analog inputs, but only between concurrent frames, as channel to
channel timing within one frame is done by hardware in CEBO-STICK.
15 Actually, the method returns earlier than the output will show the result, as some latency from host
system to the device's peripheral exist.
16 Timing depends on host computer and USB peripheral.
17 Interval between subsequent readings.
18 Pulse-length when writing high and low levels subsequently.
CEBO-STICK Reference Manual Cesys GmbH
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