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5.3. The Artifact-Based Approach
77
Table 5.3: Artifact-layer Perception API
calculation prior to the actual get i2c call, which blocks the microprocessor until
the I2C bus is ready.
The condition triggered notification method, on change, o ers atomic feature value
conditions (<, >, =) that specify when a particular sensor should send an interrupt
to the calling device, e.g. a notification if the temperature exceeds 40
C. Due to
memory constraints all conditions are treated as one-time triggers. Sequences of con-
ditions are interpreted as being logically OR connected. The continuous subscription
method o ers continuous feature value series on a timely basis. It is initiated by a
create buffer call that allocates memory for a round-robin bu er and starts the
feature value calculation on the bu er. The values are determined by a fixed time
interval, fixed time window and an identifier of a calculation function (e.g. median,
average, sum) to be performed on the feature values. Further, get buffer returns
all of the data collected so far in the bu er.
The artifact-layer is completely implemented on the Smart-Its hardware using C
[
CCS Compiler 2004
]
. For local use, when the sensor is directly connected to a
serial line of a host system, there is also a Java wrapper, implementing the same
interface.
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