56.2. A simple example
Consider the following setup. A LeCroy 4434 32-channel latching scaler resides in slot 15 of a CAMAC crate controlled by a CC-USB device. The CCUSBReadout's slow-controls server is to listen for connections on the default port (27000) on localhost with a ccusb module loaded with the name myccusb.
56.2.1. Configuring the ctlconfig.tcl
A prerequisite for communicating with the CC-USB through the slow controls server is that the a module of type "ccusb" has been loaded. A very simple ctlconfig.tcl is shown below that accomplishes only this.
# ctlconfig.tcl
# load a ccusb module into the slow-controls server named "myccusb"
Module create ccusb myccusb
 | If you do not load the ccusb module into the slow-controls server, the ccusbcamac package will not necessarily fail in an obvious manner. The connection will be made with the slow-controls server without complaint but the commands sent from the ccusbcamac procs will fail to do anything. |
Run the CCUSBReadout program. If you want to be 100% sure that the slow controls server will listen on port 27000, you can specify the command-line switch --port to be 27000. In most cases, this is not necessary because it defaults to that value.
56.2.2. The script that runs ccusbcamac commands
Below is an example of the script that the user will need to write that will connect to the server and issue commands to the scaler module living in slot 15. Make sure that the TCLLIBPATH includes the $DAQROOT/TclLibs directory, where DAQROOT is the top-level directory of the NSCLDAQ installation being used.
# Load the ccusbcamac package
package require ccusbcamac
# map the b and c to the connection information
ccusbcamac::cdconn 0 1 localhost 27000 myccusb
# ensure that the slow-controls server is listening for connections
# stop if it isn't because no further calls to ccusbcamac procs will ever
# succeed.
if {![ccusbcamac::isOnline 0 1]} {
exit
}
# create a device registry for LeCroy 4434 living in slot 15 of
# crate referenced as (b,c)=(0,1)
set reg [ ccusbcamac::cdreg 0 1 15]
# use Q-stop to read all 12 channels and demand that it doesn't
# perform more than 12 iterations.
set data [::ccusbcamac::qstop $reg 0 0 12]
# print the resulting output to stdout
foreach datum $data {
puts "$datum"
}
The user will then run the script as a separate process.