Analog Logic; Analog Ramp Symbol - Crestron SIMPL Windows User Manual

Crestron SIMPL Windows

Analog Logic

Primer – DOC. 6253
The last section introduced you to the most basic set of symbols in the SIMPL
language. With a good understanding of these symbols, you can write complex and
powerful programs. You might have noticed, however, that all of the symbols
discussed up until now have dealt exclusively with digital signals. From our
discussion in previous chapters we know that in addition to digital signals our
programs can contain analog and serial signals as well. This chapter deals with
symbols that can generate and manipulate analog signals.
Before we get into dealing with specific signals, let's make sure that we understand
why analog signals are important. Basically, each analog signal contain 16-bits of
information, unlike a digital signal which only contains 1 bit (on or off). This 16-bit
property means that analog signals can have values that range from 0 to 65,535 (2
1). It is this large range of values that make analog signals useful for controlling
devices that do not have discrete on/off controls. For example, a relay has an opened
and a closed state, each IR function on an IR driver is either being transmitted or not.
These all lend themselves to control via digital signals. However, when you consider
devices such as volume controllers, pan/tilt head controllers, and lighting dimmers,
you see examples where digital signals are not sufficient: enter analogs.
As we saw in the last chapter, each digital signal should only have one driving
source, except in certain cases where this is allowed, such as system inputs (like
button presses) and the outputs of Buffers. Analog signals have no such restrictions,
thus each signal can have as many driving sources as you deem necessary. This may
seem unnatural, and that there would be conflicting values for each signal. This is
not the case, as each signal assumes a value based on the symbol which last changes
it.
When a symbol modifies the value of one of its analog outputs, the signal connected
to that output will hold the new value and retain it until that symbol or another
symbol changes the value. In the case where a signal has more than one driving
source, the value on the signal will be based on the symbol that changed its value
last.

Analog Ramp Symbol

The Analog Ramp symbol generates an analog signal which changes linearly
whenever the 'up' or 'down' inputs are high. The 'time' parameter sets the amount
of time it takes for the output to go from 0 to 100% (or vice versa). This symbol also
has a 'mute' input, which forces the output signal to 0% on the positive-edge, and
returns it to its previous value on the negative edge, thus this input is commonly
driven by a Toggle symbol.
Each Analog Ramp symbol is ideally suited to providing volume control, as long as
the controlling device can accept an analog signal, as is the case with the CNXVTC-
3. As shown in the following example, channels A and B of the CNXVTC-3 are
being driven by the first Ramp, providing stereo volume control, and the second
Ramp controls channel C.
Software
Crestron SIMPL Windows • 57
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