VT1433B User's Guide
Using the VT1433B
Channels and groups
This section gives some information about using channels and groups. For more detailed information see the VT1433B help text.
Channel Groups
In the VT1433B VXIplug&play driver, a channel group is the basic unit of hardware control. To control any channel, it 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. This handle can then be used to direct functions to all channels in the group.
When a channel group is created, all input and tach channels in the group are automatically activated and all source channels are inactivated. But when deleted, 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, the channels in group should always be explicitly inactivated before deleting them. Channels can be inactivated with hpe1432_setActive. Channel groups can be deleted with hpe1432_deleteChannelGroup and hpe1432_deleteAllChanGroups.
Also when creating a channel group, channels which are not mentioned in the new group are not turned off. Any channels that are not to be active must be explicitly inactivated. (An exception is a
Initialization
The command used to initialize the system is hpe1432_init. This function initializes the VXIplug&play library and registers all VT1433B modules. It also checks the existence of a VT1432A module at each of the logical addresses given in the resource list and allocates logical channel identifiers for each channel in all of the VT1432As. 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 VT1433B found. hpe1432_getHWConfig returns additional information about the hardware.
After hpe1432_init is run, use hpe1432_getNumChans to get the total count of inputs, sources and tachometers for all VT1433B modules named in the hpe1432_init call.
