Sequencer: Difference between revisions

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The midas documentation has moved. See [https://midas.triumf.ca/docs/develop/features/monitoring_and_control/sequencer/ Sequencer: overview] and [https://midas.triumf.ca/docs/develop/features/monitoring_and_control/sequencer/scripting/ Sequencer: scripting] for the new documentation about the sequencer.
 
= Links =
<div style="column-count:3;-moz-column-count:3;-webkit-column-count:3">
* [[/Sequencer ODB tree]]
* [[Sequencer Page]]
* [[mhttpd]]
</div>
 
= Introduction =
A Sequencer for starting and stopping runs is part of the MIDAS distribution. It uses a simple Midas Script Language (MSL) for commands.
 
The sequencer runs as a separate process and must be started before running a sequence via the command '''msequencer'''. The first time  the  {{Button|name=Sequencer}} button on the [[Status Page]] is pressed, the ODB [[/Sequencer ODB tree|Sequencer Tree]] is created. If the Sequencer button is not present on the [[Status Page]], it may have been  [[Status Page#page-switch-buttons|suppressed]].
 
The sequencer runs scripts in MSL (Midas Script Language) format, which reside on the server (where {{Utility|name=mhttpd}} is running). The sequencer state is completely stored in the ODB, meaning that even if  {{Utility|name=mhttpd}} or the sequencer is stopped and restarted, the active sequence operation continues exactly where it has been stopped.
 
Refer to the [[/Sequencer ODB tree]] for more details on its organization.
 
For instructions on '''getting started with the sequencer''', see [[Sequencer Page]]
 
= Sequencer Commands =
The following commands are implemented in the MIDAS Sequencer. The left syntax is for the XML file, the right for the MSL (Midas Script Language).
 
Variable names are indicated in italic, options are enclosed in [brackets].
 
{| class="wikitable" style="text-align: left; color: black; tr:nth-child(even) {background-color: #F0F0F0};"
!style="width: 20%;background-color:#C0C0C0;"|MSL format
!style="width: 60%;background-color:#C0C0C0;"|Description
|-
||INCLUDE ''name''
||Include another XML file ''name''.xml
|-
||CALL ''name'', ''a'', ''b'', ''c'', ...
||Call a subroutine. Optional parameters ''a'',''b'',''c''... are passed to the subroutine, where they can be referenced via $1, $2, $3, etc. The subroutine can either reside in the current file, or in a library file which is included.
|-
||CAT ''name'', ''a'', ''b'', ''c'', ...
||Concatenates the strings ''a'',''b'',''c'',... into a single variable name . Can be referenced with $''name''. If a string must contain a comma, it can be enclosed in quotes such as in '''CAT title $run, ",", $n events'''
|-
||COMMENT ''comment''
||A comment for this XML file, for information only. This comment is shown in the title bar next to the file name if one runs a script. This can be helpful if one has many XML files and the file name only is not enough to supply enough information.
|-
||GOTO ''n''
||Jump to line ''n'' in script
|-
||IF ''con''  <br>or<br>IF (''con'')<br>
... <br>
ELSE <br>
... <br>
ENDIF
||Statements between "IF" and "ENDIF" are only executed if condition "con" is true, otherwise the statements between the optional "ELSE" and "ENDIF" are executed. The condition can use any math expression using variables via $name together with operators "<", "<=", ">", ">=", "==", "!=", "&" (bitwise AND). Up to four nested IF statements are possible. An example would be "IF ($x+3 > $y*4+$z^2)".
|-
||LIBRARY ''name''
||Indicates that the current file is a library (which can be included by other files). A library usually consists of a set of subroutines.
 
|-
||LOOP [''name'' ,] ''n'' ... ENDLOOP
||To execute a loop ''n'' times. For infinite loops, "infinite" can be specified as ''n''. Optionally, the loop variable running from 1...''n'' can be accessed inside the loop via $''name''.
 
|-
||LOOP ''name'',  ''a'', ''b'', ''c'', ... ... ENDLOOP
||Loop though a list of values. The loop is executed once for each value, which is stored into the variable ''name'' so it can be accessed inside the loop via $''name''.
 
|-
||MESSAGE ''message'' [,1]
||Opens a message box in the browser containing the text message. If wait="1", then the sequencer waits until the box is closed by the user before continuing.
|-
||ODBCREATE ''path'', ''type'' [, ''size'']
||Create an ODB key of type ''type'' and optional size ''size'' (for arrays). ''type'' can be ''UNIT8'', ''INT8'', ''UNIT16'', ''INT16'', ''UNIT32'', ''INT32'', ''BOOL'', ''FLOAT'', ''DOUBLE'', ''STRING''
|-
||ODBDELETE ''path''
||Delete an ODB key. If ''path'' points to a ODB subdirectory, delete the whole subdirectory.
|-
||ODBGET ''path'', ''name''
||To get a value from a variable ''name''. The variable can then be referenced with $''name''. If the ODB value is an array, the index can be specified like via a constant or expression:<br>
<pre>
ODBGET "/Path/key[15]", v
ODBGET "/Path/key[$i + 15]", v
</pre>
|-
||ODBINC ''path'' [, ''delta'']
||To increment a value in the ODB. ''delta'' can be positive or negative. If no "delta" is given, 1 is used.
|-
||ODBSET ''path'', ''value'' [, 0|1]
||To set a value in the ODB. ''value'' can be any math expression containing variables (preceded by a '$'). ''path'' can also contain variables (preceded by a '$'), but no math expressions.<br>
If the ODB key referenced by ''path'' is an array, the index can be specified such as<br>
<pre>
ODBSET "/Path/value[3]", 1    # individual value
ODBSET "/Path/value[3-5]", 2  # index range 3,4,5
ODBSET "/Path/value[*]", 0    # all values of array
</pre>
The path value can match multiple keys using the '?' and '*' wildcard (one or any number of characters respectively). This is useful to set the same sub-path on multiple folders:<br>
<pre>
ODBSET "/Path/to/somewhere/folder0/value", "1"
ODBSET "/Path/to/somewhere/folder1/value", "1"
ODBSET "/Path/to/somewhere/folder2/value", "1"
</pre>
can be shortened as:<br>
<pre>
ODBSET "/Path/to/somewhere/folder*/value", "1"
</pre>
The notify flag specifies if possible hot-links to this ODB value are notified. This can be useful if a front-end program has many parameters, which must be set for a specific run. The front-end usually has a hot-link to its parameters, so on each modification a callback function in the front-end is called which usually modifies some hardware. If there are many ODBSet statements for all parameters, the callback would be executed on each ODBSet, so the hardware would be reconfigured many times slowing down the startup of a run. In order to prevent this, notify="0" can be specified for all ODBSet statements except the last one which contains notify="1", so the callback function is called only once at the end.
|-
||ODBLOAD ''file'' [, ''path'']
||Load an external file into the ODB.<br>
JSON, XML and ODB file format are supported with the value inferred by the content of the file.
The optional path marks the position where to load the given file into the ODB, if no position is given the file is loaded from ODB root.<br>
For the input file several options are supported: if the filename starts with "/" is is assumed to be an absolute path, if it starts with a "$" the path starts from the Sequencer root folder stored in the ODB at /Sequencer/Path. In all other cases it is intended as a relative path to the local MSL file.
|-
||ODBSAVE ''path'', ''file''
||Save part of the ODB to an external file.<br>
The file extension is used to determine the format. Possible values are ".json", ".xml" and ".odb".
The path can point to an individual value in the ODB or to a whole subtree.<br>
For the output file several options are supported: if the filename starts with "/" is is assumed to be an absolute path, if it starts with a "$" the path starts from the Sequencer root folder stored in the ODB at /Sequencer/Path. In all other cases it is intended as a relative path to the local MSL file.
|-
||ODBSUBDIR ''path'' ...ENDODBSUBDIR
||If one wants to se several ODB values in the same directory, the ODBSet commands can be rather long if the path is long. Using this command, the subdir can be specified for all commands between the opening and ending tags. So instead of writing <br>
<pre>
ODBSET /Very/long/path/into/the/odb/value1, 1
ODBSET /Very/long/path/into/the/odb/value2, 1
ODBSET /Very/long/path/into/the/odb/value3, 1
ODBSET /Very/long/path/into/the/odb/value4, 1
</pre>
one can write <br>
<pre>
ODBSUBDIR /Very/long/path/into/the/odb
ODBSET value1, 1
ODBSET value2, 1
ODBSET value3, 1
ODBSET value4, 1
ENDODBSUBDIR
</pre>
|-
||PARAM ''name'', ''comment'', [''a'',''b'',''c'' | bool]
||When starting a script, a start page is shown where one can enter additional parameters for the script. Parameters can be defined either centrally for all scripts in the ODB under /Experiment/Edit on sequence. This subdirectory in the ODB can contain links to ODB values, which are queried at the start page. In addition, each script can define additional parameters appended to this list. They will be stored under /Sequencer/Variables and can be referenced inside the script via $name, where name can be any variable name specified in the parameter statement. The optional "comment" is shown on the start page below the parameter name. If only certain options are possible for the parameter, they can be defined via the options list. The web page will then contain a drop-down list showing the options. In case of type="bool", a checkbox will be shown.
|-
||RUNDESCRIPTION ''description''
||a run description which is stored under /Experiment/Run Parameters/Run Description .
|-
||SCRIPT ''script'' [, a, b, c, ...]
||To call a script on the server side. Optionally, pass parameters to the script.
|-
||SET ''name'', ''value''<br>
or<br>
''name'' = ''value''
||Sets the variable ''name'' to "value". The variable can then be referenced later in the script by putting a "$" in front of the name like $"name". ''value'' can be a simple number or a complex expression containing other variables (preceded by a ''$'') and calculations such as ''$v + 3*$x * sin($t)''. Following functions are available: ''abs, acos, asin, atan, atan2, ceil, cos. cosh, e, exp, fac, floor, ln, log, pi, pow, sin, sinh, sqrt, tan, tanh''. A variable can be an array by using square brackets, like "a[10] = 5" or "x = $a[10]".
|-
||SUBROUTINE ''name'' ... ENDSUBROUTINE
||Declares a subroutine which can be called via CALL.
|-
||TRANSITION start | stop | pause | resume
||To start, stop, pause or resume a run
|-
||WAIT events | ODBvalue | seconds, [''ODB path''], [''op''], [''value'']
||Wait until a number of events is acquired (testing /Equipment/Trigger/Statistics/Events sent), or until a value in the ODB exceeds value, or wait for ''value'' seconds. If the operand ''op'' is given, the ODB value is compared with value using this operand. So one could wait until an ODB value is equal to value or becomes smaller than value. Here is an example of such a statement which waits until some high voltage is below 100 V.
<pre>
WAIT ODBvalue, /Equipment/HV/Variables/Measured[3], <, 100
</pre>
|}
 
= MSL Examples =
The following example is a simple script, which writes a run description to the ODB, asks for a number of runs, then executes the runs, each running for 60 seconds.
 
<pre>
COMMENT "This is a MSL test file"
RUNDESCRIPTION "Test run"
PARAM runs
 
LOOP $runs
    TRANSITION START
    WAIT Seconds 60
    TRANSITION STOP
ENDLOOP
</pre>
 
The following script is a more complex example, which measures a I-V curve (e.g. of a SiPM detector) and stores it in the ODB. It assumes a power supply operated by a front-end and linked to /Equipment/KEYTHLEY/. The I-V curve in the ODB can be plotted with a midas custom page.
 
<pre>
#
# I-V-Curve test with parameter specification at startup
#
 
PARAM start_voltage, "Starting voltage"
PARAM stop_voltage, "Stop voltage"
PARAM num_steps, "Number of steps"
 
# Calculate step size
num_steps = $num_steps + 1 # add one step for stop_voltage
step_size = ($stop_voltage-$start_voltage) / ($num_steps-1)
 
# Initialize measurement arrays at startup
ODBCREATE /Equipment/Test/Variables/Voltage, FLOAT, $num_steps
ODBCREATE /Equipment/Test/Variables/Current, FLOAT, $num_steps
ODBCREATE /Equipment/Test/Variables/V, FLOAT
 
# Erase any previously stored array
ODBSET /Equipment/Test/Variables/Voltage[*], 0
ODBSET /Equipment/Test/Variables/Current[*], 0
 
v = $start_voltage
ODBSET /Equipment/Test/Variables/V, $v
 
current = 0
 
# Turn on Keithley
ODBSET /Equipment/KEITHLEY/Variables/Set State, 1
# Wait to turn on
WAIT SECONDS, 2
 
 
# Looping starts at 1
LOOP i, $num_steps
    # Store voltage in array and in variable
    ODBSET /Equipment/Test/Variables/Voltage[$i-1], $v
    ODBSET /Equipment/Test/Variables/V, $v
 
    # Set voltage and measure
    ODBSET /Equipment/KEITHLEY/Variables/Demand Voltage, $v
    # Wait for measurement to be stored in Current
    WAIT SECONDS, 10
    ODBGET /Equipment/KEITHLEY/Variables/Current, current
   
    # Outputting current to ODB array
    ODBSET /Equipment/Test/Variables/Current[$i-1], $current
 
    # increment voltage
    v = $v + $step_size
ENDLOOP
 
# Turn off Keithley
ODBSET /Equipment/KEITHLEY/Variables/Set State, 0
 
# Wait to turn off
WAIT SECONDS, 1
</pre>
 
[[Category:Sequencer]]

Latest revision as of 22:01, 30 October 2026

The midas documentation has moved. See Sequencer: overview and Sequencer: scripting for the new documentation about the sequencer.

Retrieved from "https://daq00.triumf.ca/MidasWiki/index.php?title=Sequencer&oldid=3810"