Appendix D: Signals And Their Definitions; Terminology - Rethink Robotics Baxter User Manual

Appendix D: Signals and their Definitions

This appendix discusses available signals and their exact definitions.

Terminology

Signal: a signal transmits a piece of information. Signals are binary, meaning they are only on or off.
A signal can be an input signal received by Intera from an external source or an output signal sent
by Intera to an external source.
Polarity: a binary signal is either true or false. By default, when Intera reads an input signal, it inter-
prets a zero as false and a one as true. Conversely, when it sends an output signal, it sends a zero
for false and a one for true. How zero and one relate to the real world depends upon how the exter-
nal devices are wired and configured.
Invert: Intera has the option to invert an input or output signal. An inverted signal is simply inter-
preted as opposite to the default. Namely, a zero is considered true and a one is considered false.
Signal classes: Intera uses two main types of signals:
Level: the information is contained solely in the current value of the signal. This represents
the state of something, e.g., whether a part is present or whether an operation is done. Input
level signals are used in one of two ways:
•Gate (input): Intera waits at specific points in a task for a gate signal to be true.
Once true, the value of the gate is ignored until that point in the task is reached
again. To be reliably recognized, a gate input should have a minimum duration of 0.5
seconds.
•Enable (input): Intera will wait for an enable signal to be true before executing par-
ticular actions, then requires that the enable signal remain true or it will abort the
action as soon as possible.
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Intera 3.2