APPENDIX A
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GPIO OPERATION
A
GPIO operation
Omnia VOLT offers the ability to control several functions by means of trigger events (a trigger
event is either a physical contact closure or a virtual LiveWire GPIO event). Currently, presets
may be selected, the primary and secondary input sources may be selected, and the failover state
may be set (forcing a switch to the secondary input) or cleared (forcing a restore to primary
input). Additionally, status information is available via the GPIO system when any of the above
events occur for any reason (such as front panel or remote control as well as due to trigger event
handling).
All of the above functionality is implemented via the LiveWire GPIO facilities that are part of
LiveWire Routing Protocol (LWRP). The functions are controlled by sending GPIO messages
to “virtual” LiveWire GPO ports on VOLT, and status is monitored by monitoring virtual GPI
ports. These ports are virtual in the sense that they do not correspond to any physical output
or input on the rear-panel, but instead initiate or report on actions that occur within the unit.
Outputs ports (GPO) are used to control the unit as they are an output from the network, and
can have a LiveWire GPI patched to them to make the GPI source control the Omnia. Input
ports (GPI) are used to report status from the unit as they are inputs to the network and can be
patched to a LiveWire GPO to produce a status output.
The GPI pins on the rear panel appear as a GPI port on the LiveWire network. Hence, this port
can be patched to any of VOLT’s GPO ports making it control the corresponding function (It
could also be patched anywhere on the LiveWire network instead of, or in addition to, using it
locally). The “GPIO / Events” page on VOLT’s web-based interface allows this to be done easily.
It also allows other LiveWire GPI ports to be patched to VOLT’s virtual GPO ports so that the
corresponding function could be remotely controlled. Finally, it provides a means to specify
which presets can be selected by means of GPIO events.
Full GPIO control is available by directly using LWRP on a TCP connection to port 93 of VOLT.
See the LWRP documentation for a description of this protocol itself. This document explains
how the GPIO ports and the pins within those ports are assigned on VOLT. In addition to the
pin-based protocol, there is a stateless, text command protocol using LWRP’s GPIO “CMD:”
syntax. This protocol is recommended instead of the pin-based GPIO protocol when creating
software remote control functions. The command descriptions are given below, after the port
and pin assignments.
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