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Channels and groups
This section gives some information about using channels and groups. For
more detailed information see the HP E1432A help text.
Channel Groups
In the HP E1432A VXIplug&play driver, a channel group is the basic unit of
hardware control. Any channel you want to control must first be assigned
to a group with the hpe1432_createChannelGroup function. In addition to
creating the group, this function returns a “handle” that uniquely identifies
the group. You can then use this handle to direct functions to all channels
in the group.
When you create a channel group, all input and tach channels in the group
are automatically activated and all source channels are inactivated. But
when you delete a channel group, input and tach channels are not
automatically inactivated. Any input or tach channel that remains active
after its group is deleted will continue to supply data to its module’s FIFO
buffer during a measurement—consuming module resources. For this
reason, you should always explicitly inactivate the channels in group before
deleting it. You can inactivate channels with hpe1432_setActive. You can
delete channel groups with hpe1432_deleteChannelGroup and
hpe1432_deleteAllChanGroups.
Also when you create a channel group, channels which are not mentioned
in the new group are not turned off. You must explicitly inactivate any
channels you do not wish to be active. (An exception is a power-up when
only the channels in the initial channel group are active.)
Initialization
The command used to initialize your system is hpe1432_init. This function
initializes the VXIplug&play library and registers all HP E1433A modules. It
also checks the existence of an HP E1432 module at each of the logical
addresses given in the resource list and allocates logical channel identifiers
for each channel in all of the HP E1432s. Input channels, source channels,
and tach/trigger channels are kept logically separated.
Most other functions cannot be used until after hpe1432_init, but there are
two functions which can be used before initialization to get information
needed by hpe1432_init. These are hpe1432_find and
hpe1432_getHWConfig. hpe1432_find searches the VXI mainframe and
returns the VXI Logical Address for every HP E1433A found.
hpe1432_getHWConfig returns additional information about the hardware.
After hpe1432_init has been run you can use hpe1432_getNumChans to get
the total count of inputs, sources, and tachs for all HP E1433A modules
named in the hpe1432_init call.
HP E1433A User's Guide
Using the HP E1433A
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