Symetrix Composer v7.0 Manual page 14

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Should I use the push feature or poll for
parameter changes?
The decision is up to you. Use whichever method makes
more sense for your application and control system. Manual
polling is often simpler to implement initially because all data
from the unit is a direct response to command you send
it, simplifying parsing. However, in situations where a large
number of parameters that change infrequently need to be
monitored, pushing may make more sense. You may also
prefer the convenience of not needing to set up a timer
to continually poll parameters for changes. Use whatever
method is appropriate for your situation.
How often is data pushed?
If there is data to be pushed, it is normally sent out every
100 milliseconds. This is called the push interval. While 100
ms is the default, the push interval can be changed via a Set
Push Interval (PUI) command.
Can I push meter data?
Yes, meters can be enabled for push. Keep in mind that
with normal audio signals connected to a meter, the meter
value will most likely be changing constantly, so you will
typically see the meter data being pushed at every 100 ms
interval. However, a Set Push Threshold command can be
used to prevent pushes until the data differs by a specified
amount (by default, this amount is 1). Another option is to
use an LED display, peak detector, and/or threshold detector
modules instead of directly pushing the meter date.
How can I control the amount of data
pushed?
There are several methods for controlling pushed data. First,
since pushed data is enabled on a per-control basis, your first
line of defense is to limit it to only certain controls. Second,
pushing can be globally turned on and off using this protocol.
Third, pushing can be enabled for just a range of controller
numbers. Fourth, the Set Push Threshold command can be
used to prevent pushes until the data changes by a specified
amount. Fifth, the Set Push Interval command controls how
often the data is pushed, useful for meters and other data that
changes frequently. Finally, the Push Refresh and Push Clear
commands provide additional methods of control.
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I want to refresh everything to make sure
my control system is synchronized to the
hardware. How can I receive all data even if
it hasn't changed?
Use the Push Refresh (PUR) (GC) command. Alternatively,
you could use the Get Controller commands to manually ask
for the controls you are concerned with.
Sometimes my control system turns off
push for an extended period of time. When
I turn it on, will I be notified of all changes
that occurred while push was turned off?
Yes, by default, all changes made while push was off will be
immediately reported as soon as it is turned on. This applies
to both turning push off globally or for individual controllers
via the Push Disable command. Take care that your system
can handle the potentially large amount of data that can
be generated. It may be helpful to "gradually" turn on the
push feature, enabling a small range of controller numbers
at once. You can also use the Push Clear command to
deal with this scenario. It allows you to effectively ignore all
previous unreported changes.
What is the difference between the Global
Push Enable/Disable (PU) command
and the Push Enable (PUE) and Push
Disable (PUD) commands? Why are there
2 different ways to specify a range of
controllers?
The Global Push Enable/Disable command can be used to
completely turn off push, or turn on push for all or a single
contiguous range of controller numbers. In contrast, the
Push Enable/Disable command allows much finer control.
Individual (non-contiguous) controllers can be turned on and
off, hence multiple ranges are supported.
The reason both methods are provided is for backwards
compatibility. The less flexible "single range" global PU
command was added first. Later, the more flexible PUE and
PUD commands were added as an enhancement. The older
global method was left in so existing programs wouldn't
need to be modified. We recommend that you use either
one system or the other exclusively. Do not combine them.
New designs should use the PUE and PUD commands and
never use the PU command with a range specified.
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Push Commands