| NSCL Ring buffer DAQ tutorial | ||
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In order to facilitate migration to the new ringdaq software, several utilities have been written that allow spdaq client software to attach to ring buffer data with little or no modification. This appendix briefly describes these utilities and provides some examples of their use.
The utilities address three areas of compatibility:
Event file format.
SpecTcl pipe data sources
Hoisting data to systems that are not running nscldaq software
Event file format. The eventlog-compat script provides an event logger that the ReadoutShell GUI can use to log event data in SPDAQ compatible format. Readout Shell has been enhanced so that alternative event loggers can be used. This combination allows you to run experiments recording data directly in SPDAQ compatible format.
When Readout shell starts, it looks for the environment variable EVENTLOGGER if this is defined it is assumed to be the full absolute path to an event logging program which will be used instead of the default eventlog. The example belows shows how to make use of this to write event data directly in SPDAQ format
Example C-1. Writing event data in SPDAQ format
export EVENTLOGGER=/usr/opt/daq/10.0/bin/eventlog-compat
Piping SPDAQ formatted data to SpecTcl. The spectcldaq provides a SpecTcl pipe data source that sends data to SpecTcl in SPDAQ format. This allows you to attach unmodified SpecTcl applications to the ring buffer DAQ system.
The example below is a Tcl proc that allows you to make use of this facility:
Example C-2. Piping SPDAQ formatted event data to SpecTcl
proc attachOnline host {
global tcl_platform
global env
set user $tcl_platform(user)
set daqroot $env(DAQROOT)
set spectcldaq [file join $daqroot bin spectcldaq]
attach -pipe $spectcldaq tcp://$host/$user
start
}
The software assumes the environment variable DAQROOT is defined and is the top level directory of the ringdaq installation (e.g. /usr/opt/daq/10.0/bin). The script further assumes that the readout source is putting data into its default ring. Note that as with Spectrodaq, using localhost when you want data from the same system is preferred over specifying the hostname.
Serving SPDAQ data to non NSCLDAQ systems (e.g. S800 Mac). The spectcldaq.server script implements a server that allows connecting systems to get SPDAQ formatted data across a TCP/IP client/server connection. This can be used to send data to the S800 Mac SpecTcl diagnostics.
spectcldaq.server must be parameterized with the URL of the ring buffer into which Readout is putting data as well as the the port on which it listens. Any connecting client will receive data in SPDAQ fromat along its socket until it disconnects.
The next pair of examples shows how to start the server in the spdaq system that provides data listening on port 1100, and how to provide a pipe data source to SpecTcl using the server.
Example C-3. Running spectcldaq.server in an Spdaq system.
$DAQROOT/bin/spectcldaq.server tcp://localhost/`whoami` 1100
The example above assumes DAQROOT points to the base of the ringdaq directory tree (.e.g export DAQROOT=/usr/opt/daq/10.0), and that the Readout software is putting data into its default ring. Note that when accessing rings that are local to the machine the use of localhost is preferred in the ring url.
Example C-4. SpecTcl pipe data source using spectcldaq.server
proc attnet {host port} {
attach -pipe netcat $host $port
start
}
This proc makes use of the netcat utility which connects to a TCP/IP host/port pair and outputs data from that connection on its stdout. netcat is available on all Linux systems and is avaialble in the Darwin ports repository for OS-X, ( http://www.darwinports.info/ports/net/netcat.html) as well as being available in source form under the GPL (http://netcat.sourceforge.net/).