Chapter 4
Programming
4-4
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To use a virtual channel, enter its name into the channel string input of an
analog input example or subVI. If using multiple virtual channels, separate
them with commas or enter them in different elements in a channel string
array. You can enter virtual channels in any order.
Multiplexed Scanning
To perform a multiplexed scan in your application, perform the following
steps:
1.
Open an analog input example in your ADE.
2.
Enter the appropriate SCXI channel string or virtual channel string into
the channels parameter.
3.
Either enter the input limits for signals connected to your module to
adjust the gain settings in your system, or use the default gain settings
from the configuration utility, and then run the application. When
using virtual channels, the default input limits configured in the virtual
channel configurator are used.
4.
You have completed a multiplexed scan using your SCXI-1104/C.
This is not a comprehensive discussion of SCXI scanning using LabVIEW,
BridgeVIEW, Measure, or ComponentWorks, but should give you enough
information to help you get started with the examples that are shipped with
these software packages.
C and Low-Level DAQ Functions
When using a C-based environment, several steps are needed to configure
the SCXI-1104/C for multiplexed scanning. The following procedure
outlines the steps for programming with the low-level DAQ function calls:
1.
Prepare your SCXI-1104/C settings by either loading the original
SCXI configuration settings using
SCXI_Load_Config
.
2.
Specify the module scan list, the start channel of each module, and the
number of channels to scan on each module. This is done with the
function,
SCXI_SCAN_Setup
. This function accepts an array of start
channels and an array of the number of channels to scan in each
module. Therefore, it is not possible to repeat channels or use
nonsequential channels using this function.
3.
Next, use
SCXI_MuxCtr_Setup
to program the DAQ device with the
correct number of channels multiplexed per scan. This number must
match the total number of channels programmed in step two.
