Lectrosonics PT3 - Manual (Page 20)

the channel turn on briefly, then switch off again. Such a channel should use the AXlink Pulse mapping, so that the
action happens only once when the channel switches from off to on, and not again when the channel switches from
on to off.
Sometimes it is desirable to have a channel remain on for as long as some state is active. A good example would be
the use of a single button to toggle between muted and unmuted status. In this case, the button should be defined in
the AXCESS program as a latching button, by including it in the DEFINE_LATCHING section. The button is then
mapped as a straightforward channel mapping. The channel turning on invokes the action with its maximum value,
and the channel turning off invokes the action with the value zero. A volume action could thus be mapped to a
channel and used as a mute/unmute function. For more detailed information on values and how they relate to actions,
please refer to the ADVANCED CONCEPTS section.
DETECTING AXLINK DEVICES
The AMX master and connected AXlink-compatible devices all power up at different rates. It is also possible for a
transient problem to briefly take one or more devices offline. Rather than use clumsy delays, AMX Corp. recommends
robust programming techniques so your AXCESS program will work correctly no matter what devices are connected
or not connected. Do not place device initialization in the DEFINE_STARTUP section as it might be executed before
the device is ready to act on it.
The recommended practice is to use variables to keep track of whether or not each device is online, then use the
DEVICE_ID function in the mainline to update the status of each. Using IF statements in the mainline, you can then
ensure that each device is initialized properly when it comes online, and that your application will not start if a required
device is not ready.
INITIALIZING AXLINK LEVELS
Setting an AXlink level in software will normally cause the level change to propagate to the PT3 as programmed.
However, the AMX system is intelligent about level changes, and if it determines that the level is merely being reset to
its present setting, no external AXlink message is generated, and the PT3 will not be notified. To ensure that a level
change will be transmitted in all cases, AMX Corp. recommends setting the level to a value one off from the desired
value, then to the desired value. Since connected levels track together at all times that the devices involved are
online, this technique need only be used during device initialization.
AVOIDING FEEDBACK LOOPS
If a single LecNet parameter is being simultaneously manipulated from more than one control, the temptation may
arise to use a monitor to keep the controls synchronized. This practice is best avoided, as time delays in the system
and disparity between certain LecNet “set” and “get” commands frequently yield loops in which the user must “fight” to
set the control satisfactorily.
Where practical, Lectrosonics recommends that you keep track of device status in your AXCESS program and
monitor only those settings which can change independently of your code. In situations where simultaneous control
and monitoring must be accomplished, Lectrosonics recommends using separate controls to set and read the param­
eter. For the common case of a volume control and associated mute button, the simple approach of programming the
mute button to force the volume to 0 offers reliable operation and good performance without the need for a monitor.
ADVANCED CONCEPTS
This section treats some of the more subtle aspects of the PT3 in depth, and suggests a few shortcuts for frequent
use.
MULTIPLE ACTIONS FROM A SINGLE TRIGGER
To associate multiple actions with a single trigger, create an action map entry for each action, and assign the same
trigger type and trigger ID to each. When that trigger event occurs, all the associated actions will be executed in the
order in which they occur in the action map. You may use the Up and Down buttons to reorder the entries. Actions
sharing a common trigger need not be listed together in the action map in order to work together, however listing them
together is recommended.
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