This page documents both basic and advanced use of the RTT Lua bindings by example. More formal API documentation is available here.
As of orocos toolchain-2.6 the deployment component launched by rttlua has been renamed from deployer to Deployer. This is to remove the differences between the classical deployer and rttlua and to facilitate portable deployment scripts. This page has been updated to use the new, uppercase name. If you are using an orocos toolchain version prior to 2.6, replace use "deployer" instead.
Lua is a simple, small and efficient scripting language. The Lua RTT bindings provide access to most of the RTT API from the Lua language. Use-cases are:
To this end RTT-Lua consists of:
Most information here is valid for all three approaches. If not, this is explicitly mentioned. The listings are shown as interactively entered into the rttlua- REPL (read-eval-print loop), but could just the same be stored in a script file.
Currently RTT-Lua is in OCL. Is is enabled by default but will only be built if the Lua-5.1 dependency (Debian: liblua5.1-0-dev, liblua5.1-0, lua5.1) is found.
CMake options:
BUILD_LUA_RTT: enable this to build the rttlua shell, the Lua component, and the Lua plugin.BUILD_LUA_RTT_DYNAMIC_MODULES: (EXPERIMENTAL) build RTT and deployer as pure Lua plugins. Not recommended unless you know what you are doing.BUILD_LUA_TESTCOMP: build a simple testcomponent that is used for testing the bindings. Not required for normal operation.rttlib.lua is a Lua module, which is not strictly necessary, but highly recommended to load as it adds various syntactic shortcuts and pretty printing (Many examples on this page will not work without!). The easiest way to load it is to setup the LUA_PATH variable:
export LUA_PATH=";;$HOME/src/git/orocos/ocl/lua/modules/?.lua"
If you are a orocos_toolchain_ros user and do not want to hardcode the path like this, you can source the following script in your .bashrc:
#!/bin/bash RTTLUA_MODULES=`rospack find ocl`/lua/modules/?.lua if [ "x$LUA_PATH" == "x" ]; then LUA_PATH=";" fi export LUA_PATH="$LUA_PATH;$RTTLUA_MODULES"
$ ./rttlua-gnulinux OROCOS RTTLua 1.0-beta3 / Lua 5.1.4 (gnulinux) >
or for orocos_toolchain_ros users:
$ rosrun ocl rttlua-gnulinux OROCOS RTTLua 1.0-beta3 / Lua 5.1.4 (gnulinux) >
Now we have a Lua REPL that is enhanced with RTT specific functionality. In the following RTT-Lua code is indicated by a ">" prompt, while shell scripts are shown with the typical "$".
Before doing anything it is recommended to load rttlib. Like any Lua module this can be done with the require statement. For example:
$ ./rttlua-gnulinux OROCOS RTTLua 1.0-beta3 / Lua 5.1.4 (gnulinux) > require("rttlib") >
As it is annoying having to type this each time, this loading can automated by putting it in the ~/.rttlua dot file. This (Lua) file is executed on startup of rttlua:
require("rttlib") rttlib.color=true
The (optional) last line enables colors.
rttlib.stat() Print information about component instances and their state> rttlib.stat() Name State isActive Period lua PreOperational true 0 Deployer Stopped true 0
rttlib.info() Print information about available components, types and services> rttlib.info() services: marshalling scripting print LuaTLSF Lua os typekits: rtt-corba-types rtt-mqueue-transport rtt-types OCLTypekit types: ConnPolicy FlowStatus PropertyBag SendHandle SendStatus TaskContext array bool bools char double float int ints rt_string string strings uint void comp types: OCL::ConsoleReporting OCL::FileReporting OCL::HMIConsoleOutput OCL::HelloWorld OCL::LuaComponent OCL::LuaTLSFComponent OCL::TcpReporting ...
Here:
> tc = rtt.getTC()
Above code calls the getTC() function, which returns the current TC and stores it in a variable 'tc'. For showing the interface just write =tc. In the repl the equal sign is a shortcut for 'return', which in turn causes the variable to be printed. (BTW: This works for displaying any variable)
> =tc TaskContext: lua state: PreOperational isActive: true getPeriod: 0 peers: Deployer ports: properties: lua_string (string) = // string of lua code to be executed during configureHook lua_file (string) = // file with lua program to be executed during configuration operations: bool exec_file(string const& filename) // load (and run) the given lua script bool exec_str(string const& lua-string) // evaluate the given string in the lua environment
Since (rttlua beta5) the above does not print the standard TaskContext operations anymore. To print these, use tc:show().
(Yes, you really want this)
Get it here. Checkout the README for the (simple) compilation and setup.
rttlua does not offer persistent history like in the taskbrowser. If you want it, you can use rlwrap and to wrap rttlua as follows:
alias rttlua='rlwrap -a -r -H ~/.rttlua-history rttlua-gnulinux'
If you run 'rttlua' it should have persistent history.
Most modern editors provide basic syntax highlighting for Lua code.
The following shows the basic API, see section Automatically creating and cleaning up component interfaces for a more convenient way add/remove ports/properties.
Both In- and OutputPorts optionally take a second string argument (name) and third argument (description).
For this the ports don't have to be added to the TaskContext:
The rttlua-* REPL automatically creates a deployment component that is a peer of the lua taskcontext:
> tc = rtt.getTC() > depl = tc:getPeer("Deployer") > cp=rtt.Variable("ConnPolicy") > =cp {data_size=0,type="DATA",name_id="",init=false,pull=false,transport=0,lock_policy="LOCK_FREE",size=0} > depl:connect("compA.port1","compB.port2", cp)
> rttlib.info() services: marshalling, scripting, print, os, Lua typekits: rtt-types, rtt-mqueue-transport, OCLTypekit types: ConnPolicy, FlowStatus, PropertyBag, SendHandle, SendStatus, TaskContext, array, bool, bools, char, double, float, int, ints, rt_string, string, strings, uint, void comp types: OCL::ConsoleReporting, OCL::FileReporting, OCL::HMIConsoleOutput, OCL::HelloWorld, OCL::LuaComponent, OCL::TcpReporting, OCL::TimerComponent, OCL::logging::Appender, OCL::logging::FileAppender, OCL::logging::LoggingService, OCL::logging::OstreamAppender, TaskContext
> cp = rtt.Variable("ConnPolicy") > =cp {data_size=0,type="DATA",name_id="",init=false,pull=false,transport="default",lock_policy="LOCK_FREE",size=0} > cp.data_size = 4711 > print(cp.data_size) 4711
Printing the available constants:
> =rtt.globals {SendNotReady=SendNotReady,LOCK_FREE=2,NewData=NewData,SendFailure=SendFailure,\ SendSuccess=SendSuccess,NoData=NoData,UNSYNC=0,LOCKED=1,OldData=OldData,BUFFER=1,DATA=0} >
Accessing constants - just index!
> =rtt.globals.LOCK_FREE 2
It is cumbersome to initalize complex types with many subfields:
> tc = rtt.getTC() > depl = tc:getPeer("Deployer") > depl:import("kdl_typekit") > t=rtt.Variable("KDL.Frame") > =t {M={Z_y=0,Y_y=1,X_y=0,Y_z=0,Z_z=1,Y_x=0,Z_x=0,X_x=1,X_z=0},p={Y=0,X=0,Z=0}} > t.M.X_x=3 > t.M.Y_x=2 > t.M.Z_x=2.3 ...
To avoid this, use the fromtab() method:
> t:fromtab({M={Z_y=1,Y_y=2,X_y=3,Y_z=4,Z_z=5,Y_x=6,Z_x=7,X_x=8,X_z=9},p={Y=3,X=3,Z=3}})
or even shorter using the table-call syntax of Lua,
> t:fromtab{M={Z_y=1,Y_y=2,X_y=3,Y_z=4,Z_z=5,Y_x=6,Z_x=7,X_x=8,X_z=9},p={Y=3,X=3,Z=3}}
When you created an RTT array type, the initial length will be zero. You must set the length of an array before you can assign elements to it (starting from toolchain-2.5 fromtab will do this automatically:
> ref=rtt.Variable("array") > ref:resize(3) > ref:fromtab{1,1,10} > print(ref) -- prints {1,1,10} ...
> p1=rtt.Property("double", "p-gain", "Proportional controller gain")
(Note: the second and third argument (name and description) are optional and can also be set when adding the property to a TaskContext)
> tc=rtt.getTC() > tc:addProperty(p1) > =tc -- check it is there...
> tc=rtt.getTC() > pgain = tc:getProperty("pgain") > =pgain -- will print it
> p1:set(3.14) > =p1 -- a property can be printed! p-gain (double) = 3.14 // Proportional controller gain
In particular, the following will not work:
> p1=3.14
Lua works with references! This will assign the variable p1 a numeric value of 3.14 and the reference to the property is lost.
> print("the value of " .. p1:info().name .. " is: " .. p1:get()) the value of p-gain is: 3.14
Assume a property of type KDL::Frame. Similarily to Variables the subfields can be accessed by using the dot syntax:
> d = tc:getPeer("Deployer") > d:import('kdl_typekit') > f=rtt.Property('KDL.Frame') > =f (KDL.Frame) = {M={Z_y=0,Y_y=1,X_y=0,Y_z=0,Z_z=1,Y_x=0,Z_x=0,X_x=1,X_z=0},p={Y=0,X=0,Z=0}} // > f.M.Y_y=3 > =f.M.Y_y 3 > f.p.Y=1 > =f (KDL.Frame) = {M={Z_y=0,Y_y=3,X_y=0,Y_z=0,Z_z=1,Y_x=0,Z_x=0,X_x=1,X_z=0},p={Y=1,X=0,Z=0}} // >
Like Variables, Properties feature a fromtab method to initalize a Property from values in a Lua table. See Section RTT Types and Typekits - Convenient initalization of multi-field types for details.
As properties are not automatically garbage collected, property memory must be managed manually:
> tc:removeProperty("p-gain") > =tc -- p-gain is gone now > p1:delete() -- delete property and free memory > =p1 -- p1 is 'dead' now. userdata: 0x186f8c8
Synchronous calling of operations from Lua:
> d = tc:getPeer("Deployer") > =d:getPeriod() 0
> d = tc:getPeer("Deployer") > op = d:getOperation("getPeriod") > =op -- can be printed! double getPeriod() // Get the configured execution period. -1.0: no thread ... > =op() -- call it 0
"Sending" Operations permits to asynchronously request an operation to be executed and collect the results at a later point in time.
> d = tc:getPeer("Deployer") > op = d:getOperation("getPeriod") > handle=op:send() -- calling it > =handle:collect() SendSuccess 0
Note:
collect() returns multiple arguments: first a SendStatus string ('SendSuccess', 'SendFailure') followed by zero to many output arguments of the operation.collect blocks until the operation was executed, collectIfDone() will immediately return (but possibly with 'SendNotReady')Answer: No.
Workaround: define a new TaskContext that inherits from LuaComponent and add the Operation there. Implement the necessary glue between C++ and Lua by hand (not hard, but some manual work required).
Answer: No (but potentially it would be easy to add. Ask on the ML).
For example, to load the marshalling service in a component and then to use it to write a property (cpf) file:
> tc=rtt.getTC() > depl=tc:getPeer("Deployer") > depl:loadService("lua", "marshalling") -- load the marshalling service in the lua component true > =tc:provides("marshalling"):writeProperties("props.cpf") true
A second (and slightly faster) option is to get the Operation before calling it:
> -- get the writeProperties operation ... > writeProps=tc:provides("marshalling"):getOperation("writeProperties") > =writeProps("props.cpf") -- and call it to write the properties to a file. true
> depl:loadService("lua", "marshalling") -- load the marshalling service > depl:loadService("lua", "scripting") -- load the scripting service > print(tc:provides()) Service: lua Subservices: marshalling, scripting Operations: activate, cleanup, configure, error, exec_file, exec_str, getPeriod, inFatalError, inRunTimeError, isActive, isConfigured, isRunning, setPeriod, start, stop, trigger, update Ports: Service: marshalling Subservices: Operations: loadProperties, readProperties, readProperty, storeProperties, updateFile, updateProperties, writeProperties, writeProperty Ports: Service: scripting Subservices: Operations: activateStateMachine, deactivateStateMachine, eval, execute, getProgramLine, getProgramList, getProgramStatus, getProgramStatusStr, getProgramText, getStateMachineLine, getStateMachineList, getStateMachineState, getStateMachineStatus, getStateMachineStatusStr, getStateMachineText, hasProgram, hasStateMachine, inProgramError, inStateMachineError, inStateMachineState, isProgramPaused, isProgramRunning, isStateMachineActive, isStateMachinePaused, isStateMachineRunning, loadProgramText, loadPrograms, loadStateMachineText, loadStateMachines, pauseProgram, pauseStateMachine, requestStateMachineState, resetStateMachine, runScript, startProgram, startStateMachine, stepProgram, stopProgram, stopStateMachine, unloadProgram, unloadStateMachine Ports: >
The RTT Global Service is useful for loading services into your application that don't belong to a specific component. Your C++ code accesses this object by calling
RTT::internal::GlobalService::Instance();
The GlobalService object can be accessed in Lua using a call to:
gs = rtt.provides()
And allows you to load additional services into the global service:
gs:require("os") -- or: rtt.provides():require("os")
Which you can access later-on again using the rtt table:
rtt.provides("os"):argc() -- returns the number of arguments of this application rtt.provides("os"):argv() -- returns a string array of arguments of this application
-- create activity for producer: period=1, priority=0, -- schedtype=ORO_SCHED_OTHER (1). depl:setActivity("producer", 1, 0, rtt.globals.ORO_SCHED_RT)
-- create activity for producer: period=0, priority=0, -- schedtype=ORO_SCHED_OTHER (1). depl:setActivity("producer", 0, 0, rtt.globals.ORO_SCHED_RT)
depl:setMasterSlaveActivity("name_of_master_component", "name_of_slave_component")
(see also the example in section How to write a RTT-Lua component)
-- deploy_app.lua require("rttlib") tc = rtt.getTC() depl = tc:getPeer("Deployer") -- import components, requires correctly setup RTT_COMPONENT_PATH depl:import("ocl") -- depl:import("componentX") -- import components, requires correctly setup ROS_PACKAGE_PATH (>=Orocos 2.7) depl:import("rtt_ros") rtt.provides("ros"):import("my_ros_pkg") -- create component 'hello' depl:loadComponent("hello", "OCL::HelloWorld") -- get reference to new peer hello = depl:getPeer("hello") -- create buffered connection of size 64 cp = rtt.Variable('ConnPolicy') cp.type=1 -- type buffered cp.size=64 -- buffer size depl:connect("hello.the_results", "hello.the_buffer_port", cp) rtt.logl('Info', "Deployment complete!")
run it:
$ rttlua-gnulinux -i deploy-app.lua
or using orocos_toolchain_ros
$ rosrun ocl rttlua-gnulinux -i deploy-app.lua
Note: The -i option makes rttlua enter interactive mode (the REPL) after executing the script. Without it would exit after finishing executing the script, which in this case is probably not what you want.
A Lua component is created by loading a Lua-script implementing zero or more TaskContext hooks in a OCL::LuaComponent. The following RTT hooks are currently supported:
bool configureHook() bool activateHook() bool startHook() void updateHook() void stopHook() void cleanupHook() void errorHook() All hooks are optional, but if implemented they must return the correct return value (if not void of course). It is also important to declare them as global (by not adding a local keyword. Otherwise they would be garbage collected and not called)
The following code implements a simple consumer component with an event-triggered input port:
require("rttlib") tc=rtt.getTC(); -- The Lua component starts its life in PreOperational, so -- configureHook can be used to set stuff up. function configureHook() inport = rtt.InputPort("string", "inport") -- global variable! tc:addEventPort(inport) cnt = 0 return true end -- all hooks are optional! --function startHook() return true end function updateHook() local fs, data = inport:read() rtt.log("data received: " .. tostring(data) .. ", flowstatus: " .. fs) end -- Ports and properties are the only elements which are not -- automatically cleaned up. This means this must be done manually for -- long living components: function cleanupHook() tc:removePort("inport") inport:delete() end
A matching producer component is shown below:
require "rttlib" tc=rtt.getTC(); function configureHook() outport = rtt.OutputPort("string", "outport") -- global variable! tc:addPort(outport) cnt = 0 return true end function updateHook() outport:write("message number " .. cnt) cnt = cnt + 1 end function cleanupHook() tc:removePort("outport") outport:delete() end
A deployment script to deploy these two components:
require "rttlib" rtt.setLogLevel("Warning") tc=rtt.getTC() depl = tc:getPeer("Deployer") -- create LuaComponents depl:loadComponent("producer", "OCL::LuaComponent") depl:loadComponent("consumer", "OCL::LuaComponent") --... and get references to them producer = depl:getPeer("producer") consumer = depl:getPeer("consumer") -- load the Lua hooks producer:exec_file("producer.lua") consumer:exec_file("consumer.lua") -- configure the components (so ports are created) producer:configure() consumer:configure() -- connect ports depl:connect("producer.outport", "consumer.inport", rtt.Variable('ConnPolicy')) -- create activity for producer: period=1, priority=0, -- schedtype=ORO_SCHED_OTHER (1). depl:setActivity("producer", 1, 0, rtt.globals.ORO_SCHED_RT) -- raise loglevel rtt.setLogLevel("Debug") -- start components consumer:start() producer:start() -- uncomment to print interface printing (for debugging) -- print(consumer) -- print(producer) -- sleep for 5 seconds os.execute("sleep 5") -- lower loglevel again rtt.setLogLevel("Warning") producer:stop() consumer:stop()
(available from toolchain-2.5)
The function rttlib.create_if can (re-) generate a component interface from a specification as shown below. Conversely, rttlib.tc_cleanup will remove and destruct all ports and properties again.
-- stupid example: iface_spec = { ports={ { name='inp', datatype='int', type='in+event', desc="incoming event port" }, { name='msg', datatype='string', type='in', desc="incoming non-event messages" }, { name='outp', datatype='int', type='out', desc="outgoing data port" }, }, properties={ { name='inc', datatype='int', desc="this value is added to the incoming data each step" } } } -- this create the interface iface=rttlib.create_if(iface_spec) function configureHook() -- it is safe to be run twice, existing ports -- will be ignored. Thus, running cleanup() and configure() -- will reconstruct the interface again. iface=rttlib.create_if(iface_spec) inc = iface.props.inc:get() return true end function startHook() -- ports/props can be indexed as follows: iface.ports.outp:write(1) return true end function updateHook() local fs, val fs, val = iface.ports.inp:read() if fs=='NewData' then iface.ports.outp:write(val+inc) end end function cleanupHook() -- remove all ports and properties rttlib.tc_cleanup() end
In contrast to Components (which typically contain functionality which is standalone), Services are useful for extending functionality of existing Components. The LuaService permits to execute arbitrary Lua programs in the context of a Component.
The following dummy example loads the LuaService into a HelloWorld component and then runs a script that modifies a property:
require "rttlib" tc=rtt.getTC() d = tc:getPeer("Deployer") -- create a HelloWorld component d:loadComponent("hello", "OCL::HelloWorld") hello = d:getPeer("hello") -- load Lua service into the HelloWorld Component d:loadService("hello", "Lua") -- Execute the following Lua script (defined a multiline string) in -- the service. This dummy examples simply modifies the Property. For -- large programs it might be better tostore the program in a separate -- file and use the exec_file operation instead. proggie = [[ require("rttlib") tc=rtt.getTC() -- this is the Hello Component prop = tc:getProperty("the_property") prop:set("hullo from the lua service!") ]] prop = hello:getProperty("the_property") -- get hello.the_property print("the_property before service call:", prop) hello:provides("Lua"):exec_str(proggie) -- execute program in the service print("the_property after service call: ", prop)
More useful than just running once is to be able to execute a function synchronously with the updateHook of the host component. This can be achieved by registering a ExecutionEngine hook (much easier than it sounds!).
The following Lua service code implements a simple monitor that tracks the currently active (TaskContext) state of the component in whose context it is running. When the state changes the new state is written to a port "tc_state", which is added to the context TC.
This code could be useful for a supervision statemachine that can then easily react to this state change by means of an event triggered port.
require "rttlib" tc=rtt.getTC() d = tc:getPeer("Deployer") -- create a HelloWorld component d:loadComponent("hello", "OCL::HelloWorld") hello = d:getPeer("hello") -- load Lua service into the HelloWorld Component d:loadService("hello", "Lua") mon_state = [[ -- service-eehook.lua require("rttlib") tc=rtt.getTC() -- this is the Hello Component last_state = "not-running" out = rtt.OutputPort("string") tc:addPort(out, "tc_state", "currently active state of TaskContext") function check_state() local cur_state = tc:getState() if cur_state ~= last_state then out:write(cur_state) last_state = cur_state end return true -- returning false will disable EEHook end -- register check_state function to be called periodically and -- enable it. Important: variables like eehook below or the -- function check_state which shall not be garbage-collected -- after the first run must be declared global (by not declaring -- them local with the local keyword) eehook=rtt.EEHook('check_state') eehook:enable() ]] -- execute the mon_state program hello:provides("Lua"):exec_str(mon_state)
Note: the -i option causes rttlua to go to interactive mode after executing the script (and not exiting afterwards).
$ rttlua-gnulinux -i service-eehook.lua > rttlib.portstats(hello) the_results (string) = the_buffer_port (string) = NoData tc_state (string) = Running > hello:error() > rttlib.portstats(hello) the_results (string) = the_buffer_port (string) = NoData tc_state (string) = RunTimeError >
It is often useful to validate a deployed system at runtime, however you want to avoid cluttering individual components with non-functional validation code. Here's what to do (Please also see this post on orocos-users, which inspired the following)
Use-case: check for unconnected input ports
1. Write a function to validate a single component
The following function accepts a TaskContext as an argument and checks wether it has unconnected input ports. If yes it prints an error.
function check_inport_conn(tc) local portnames = tc:getPortNames() local ret = true for _,pn in ipairs(portnames) do local p = tc:getPort(pn) local info = p:info() if info.porttype == 'in' and info.connected == false then rtt.logl('Error', "InputPort " .. tc:getName() .. "." .. info.name .. " is unconnected!") ret = false end end return ret end
2. After deployment, execute the validation function on all components:
This can be done using the mappeers function.
rttlib.mappeers(check_inport_conn, depl)
The mappeers function is a special variant of map which calls the function given as a first argument on all peers reachable from a TaskContext (given as a second argument). We pass the Deployer here, which typically knows all components.
Here's a dummy deployment example to illustrate:
require "rttlib" tc=rtt.getTC() depl=tc:getPeer("Deployer") -- define or import check_inport_conn function here -- dummy deployment, ports are left unconnected. depl:loadComponent("hello1", "OCL::HelloWorld") depl:loadComponent("hello2", "OCL::HelloWorld") rttlib.mappeers(check_inport_conn, depl)
Executing it will print:
0.155 [ ERROR ][/home/mk/bin//rttlua-gnulinux::main()] InputPort hello1.the_buffer_port is unconnected! 0.155 [ ERROR ][/home/mk/bin//rttlua-gnulinux::main()] InputPort hello2.the_buffer_port is unconnected!
rFSM is a fast, lightweight Statechart implementation is pure Lua. Using RTT-Lua rFSM Statecharts can conveniently be used with RTT. The rFSM sources can be found here.
Answer:
Typically a Component will be preferred when
A Service is preferred when
There will, undoubtly, be exceptions!
Summary: Create a OCL::LuaComponent. In configureHook load and initalize the fsm, in updateHook call rfsm.run(fsm)
(see the rFSM docs for general information)
The source code for this example can be found here.
It is a best-practice to split the initalization (setting up required functions, peers or ports used by the fsm) and the fsm model itself into two files. This way the fsm model is kept as platform independent and hence reusable as possible.
The following initalization file is executed in the newly create LuaComponent for preparing the environment for the statemachine, that is loaded and initalized in configureHook.
launch_fsm.lua
require "rttlib" require "rfsm" require "rfsm_rtt" require "rfsmpp" local tc=rtt.getTC(); local fsm local fqn_out, events_in function configureHook() -- load state machine fsm = rfsm.init(rfsm.load("fsm.lua")) -- enable state entry and exit dbg output fsm.dbg=rfsmpp.gen_dbgcolor("rfsm-rtt-example", { STATE_ENTER=true, STATE_EXIT=true}, false) -- redirect rFSM output to rtt log fsm.info=function(...) rtt.logl('Info', table.concat({...}, ' ')) end fsm.warn=function(...) rtt.logl('Warning', table.concat({...}, ' ')) end fsm.err=function(...) rtt.logl('Error', table.concat({...}, ' ')) end -- the following creates a string input port, adds it as a event -- driven port to the Taskcontext. The third line generates a -- getevents function which returns all data on the current port as -- events. This function is called by the rFSM core to check for -- new events. events_in = rtt.InputPort("string") tc:addEventPort(events_in, "events", "rFSM event input port") fsm.getevents = rfsm_rtt.gen_read_str_events(events_in) -- optional: create a string port to which the currently active -- state of the FSM will be written. gen_write_fqn generates a -- function suitable to be added to the rFSM step hook to do this. fqn_out = rtt.OutputPort("string") tc:addPort(fqn_out, "rFSM_cur_fqn", "current active rFSM state") rfsm.post_step_hook_add(fsm, rfsm_rtt.gen_write_fqn(fqn_out)) return true end function updateHook() rfsm.run(fsm) end function cleanupHook() -- cleanup the created ports. rttlib.tc_cleanup() end
A dummy statemachine stored in the fsm.lua file:
return rfsm.state { ping = rfsm.state { entry=function() print("in ping entry") end, }, pong = rfsm.state { entry=function() print("in pong entry") end, }, rfsm.trans {src="initial", tgt="ping" }, rfsm.trans {src="ping", tgt="pong", events={"e_pong"}}, rfsm.trans {src="pong", tgt="ping", events={"e_ping"}}, }
Option A: Running the rFSM example with a Lua deployment script
deploy.lua
-- alternate lua deploy script require "rttlib" tc=rtt.getTC() d=tc:getPeer("Deployer") d:import("ocl") d:loadComponent("Supervisor", "OCL::LuaComponent") sup = d:getPeer("Supervisor") sup:exec_file("launch_fsm.lua") sup:configure() cmd = rttlib.port_clone_conn(sup:getPort("events"))
Run it. cmd is an inverse (output) port which is connected to the incoming (from POV of the fsm) 'events' port of the fsm, so by writing to it we can send events:
$ rosrun ocl rttlua-gnulinux -i deploy.lua OROCOS RTTLua 1.0-beta3 / Lua 5.1.4 (gnulinux) INFO: created undeclared connector root.initial > sup:start() > in ping entry > cmd:write("e_pong") > in pong entry > cmd:write("e_ping") > in ping entry > cmd:write("e_pong") > in pong entry
Option B: Running the rFSM example with an Orocos deployment script
deploy.ops
import("ocl") loadComponent("Supervisor", "OCL::LuaComponent") Supervisor.exec_file("launch_fsm.lua") Supervisor.configure
After starting the supervisor we 'leave' it, so we can write to the 'events' ports:
$ rosrun ocl deployer-gnulinux -s deploy.ops INFO: created undeclared connector root.initial Switched to : Deployer This console reader allows you to browse and manipulate TaskContexts. You can type in an operation, expression, create or change variables. (type 'help' for instructions and 'ls' for context info) TAB completion and HISTORY is available ('bash' like) Deployer [S]> cd Supervisor TaskBrowser connects to all data ports of Supervisor Switched to : Supervisor Supervisor [S]> start = true Supervisor [R]> in ping entry Supervisor [R]> leave Watching Supervisor [R]> events.write ("e_pong") = (void) Watching Supervisor [R]> in pong entry Watching Supervisor [R]> events.write ("e_ping") = (void) Watching Supervisor [R]> in ping entry Watching Supervisor [R]>
This is basically the same as executing a function periodally in a service (see the Service example above). There is a convenience function service_launch_rfsm in rfsm_rtt.lua to make this easier.
The steps are:
require "rfsm_rtt" -- get reference to exec_str operation fsmfile = "fsm.lua" execstr_op = comp:provides("Lua"):getOperation("exec_str") rfsm_rtt.service_launch_rfsm(fsmfile, execstr_op, true)
The last line means the following: launch fsm in <fsmfile> in service identified by execstr_op, true: create an execution engine hook so that the rfsm.step is called at the component frequency. (See the generated rfsm_rtt API docs).
Generally speaking, the most effective way of creating a new FSM from a parent one is populating the original simple states by overriding them with composite states. In this context, the parent FSM provides “empty” boxes to be filled with application-specific code.
In the following example, “daughter_fsm.lua” loads “mother_fsm.lua” and overrides a state, two transitions and a function. “daughter_fsm.lua” is launched by a Lua Orocos component named “fsm_launcher.lua” . Deployment is done by “deploy.ops” . Instructions on how to run the example follow.
mother_fsm.lua
-- mother_fsm.lua is a basic fsm with 2 simple states return rfsm.state { StateA = rfsm.state { entry=function() print("in state A") end, }, StateB = rfsm.state { entry=function() print("in state B") end, }, -- consistent transition naming makes overriding easier rfsm.trans {src="initial", tgt="StateA" }, tr_A_B = rfsm.trans {src="StateA", tgt="StateB", events={"e_mother_A_to_B"}}, tr_B_A = rfsm.trans {src="StateB", tgt="StateA", events={"e_mother_B_to_A"}}, }
daughter_fsm.lua
-- daughter_fsm.lua loads mother_fsm.lua -- implementing extra states, transitions and functions -- by adding and overriding the original ones. require "utils" require "rttros" -- local variables to avoid verbose function calling local state, trans, conn = rfsm.state, rfsm.trans, rfsm.conn -- path to the fsm to load local base_fsm_file = "mother_fsm.lua" -- load the original fsm to override local fsm_model=rfsm.load(base_fsm_file) -- set colored outputs indicating the current state dbg = rfsmpp.gen_dbgcolor( {STATE_ENTER=true}, false) -- Overriding StateA -- In "mother_fsm.lua" StateA is an rfsm.simple_state -- Here we make it an rfsm.composite_state fsm_model.StateA = rfsm.state { StateA1= rfsm.state { entry=function() print("in State A1") end, }, StateA2 = rfsm.state { entry=function() print("in State A2") end, }, rfsm.transition {src="initial", tgt="StateA1"}, tr_A1_A2 = rfsm.transition {src ="StateA1", tgt="StateA2", events={"e_move_to_A2"}}, tr_A2_A1 = rfsm.transition {src ="StateA2", tgt="StateA1", events={"e_move_to_A1"}}, } -- Overriding single transitions fsm_model.tr_A_to_B = rfsm.trans {src="StateA", tgt="StateB", events={"e_daughter_A_to_B"}} fsm_model.tr_B_to_A = rfsm.trans {src="StateB", tgt="StateA", events={"e_daughter_B_to_A"}} -- Overriding a specific function fsm_model.StateB.entry = function() print("I am in State B in the daughter FSM") end return fsm_model
fsm_launcher.lua
require "rttlib" require "rfsm" require "rfsm_rtt" require "rfsmpp" local tc=rtt.getTC(); local fsm local fqn_out, events_in function configureHook() -- load state machine fsm = rfsm.init(rfsm.load("daughter_fsm.lua")) -- enable state entry and exit dbg output fsm.dbg=rfsmpp.gen_dbgcolor("FSM loading example", { STATE_ENTER=true, STATE_EXIT=true}, false) -- redirect rFSM output to rtt log fsm.info=function(...) rtt.logl('Info', table.concat({...}, ' ')) end fsm.warn=function(...) rtt.logl('Warning', table.concat({...}, ' ')) end fsm.err=function(...) rtt.logl('Error', table.concat({...}, ' ')) end -- the following creates a string input port, adds it as a event -- driven port to the Taskcontext. The third line generates a -- getevents function which returns all data on the current port as -- events. This function is called by the rFSM core to check for -- new events. events_in = rtt.InputPort("string") tc:addEventPort(events_in, "events", "rFSM event input port") fsm.getevents = rfsm_rtt.gen_read_str_events(events_in) -- optional: create a string port to which the currently active -- state of the FSM will be written. gen_write_fqn generates a -- function suitable to be added to the rFSM step hook to do this. fqn_out = rtt.OutputPort("string") tc:addPort(fqn_out, "rFSM_cur_fqn", "current active rFSM state") rfsm.post_step_hook_add(fsm, rfsm_rtt.gen_write_fqn(fqn_out)) return true end function updateHook() rfsm.run(fsm) end function cleanupHook() -- cleanup the created ports. rttlib.tc_cleanup() end
deploy.ops
import("ocl") loadComponent("Supervisor", "OCL::LuaComponent") Supervisor.exec_file("fsm_launcher.lua") Supervisor.configure Supervisor.start
To test this example, run the Deployer:
rosrun ocl deployer-gnulinux -lerror -s deploy.ops
Then:
Deployer [S]> cd Supervisor TaskBrowser connects to all data ports of Supervisor Switched to : Supervisor Supervisor [R]> leave Watching Supervisor [R]> events.write ("e_move_to_A2") FSM loading example: STATE_EXIT root.StateA.StateA1 in State A2 FSM loading example: STATE_ENTER root.StateA.StateA2
A Coordinator often needs to interact with many or all other components in its vicinity. To avoid having to write peer1 = depl:getPeer("peer1") all over, you can use the following function to generate a table of peers which are reachable from a certain component (commonly the deployer):
peertab = rttlib.mappeers(function (tc) return tc end, depl)
Assume the Deployer has two peers "robot" and "controller", they can be accessed as follows:
print(peertab.robot) -- or peertab.controller:configure()
> cp=rtt.Variable("ConnPolicy") > cp.transport=3 -- 3 is ROS > cp.name_id="/l_cart_twist/command" -- topic name > depl:stream("CompX.portY", cp)
or with sweet one-liner (thx to Ruben!):
> depl:stream("CompX.portY", rtt.provides("ros"):topic("/l_cart_twist/command"))
This is sometimes usefull for loading scripts etc. that are located in different packages.
The rttros.lua collects some basic but useful stuff for interacting with ROS. This one is "borrowed" from the excellent roslua:
> require "rttros" > =rttros.find_rospack("geometry_msgs") /home/mk/src/ros/unstable/common_msgs/geometry_msgs >
Lua has to work with two typesystems: its own and the RTT typesystem. To makes this as smooth as possible the basic RTT types are automatically converted to their corresponding Lua types as shown by the table below:
| RTT | Lua |
|---|---|
| bool | boolean |
| float | number |
| double | number |
| uint | number |
| int | number |
| char | string |
| string | string |
| void | nil |
This conversion is done in both directions: basic values read from ports or basic return values of operation are converted to Lua; vice versa if an operation with basic Lua values is called these will automatically be converted to the corresponding RTT types.
In short: write a function which accepts a lua table representation of you data type and returns either a table or a string. Assign it to rttlib.var_pp.mytype, where mytype is the value returned by the var:getType() method. That's all!
Quick example: ConnPolicy type
(This is just an example. It has been done for this type already).
The out-of-box printing of a ConnPolicy will look as follows:
./rttlua-gnulinux Orocos RTTLua 1.0-beta3 (gnulinux) > return rtt.Variable("ConnPolicy") {data_size=0,type=0,name_id="",init=false,pull=false,transport=0,lock_policy=2,size=0}
This not too bad, but we would like to display the string representation of the C++ enums type and lock_policy. So we must write a function that returns a table...
function ConnPolicy2tab(cp) if cp.type == 0 then cp.type = "DATA" elseif cp.type == 1 then cp.type = "BUFFER" else cp.type = tostring(cp.type) .. " (invalid!)" end if cp.lock_policy == 0 then cp.lock_policy = "UNSYNC" elseif cp.lock_policy == 1 then cp.lock_policy = "LOCKED" elseif cp.lock_policy == 2 then cp.lock_policy = "LOCK_FREE" else cp.lock_policy = tostring(cp.lock_policy) .. " (invalid!)" end return cp end
and add it to the rttlib.var_pp table of Variable formatters as follows:
rttlib.var_pp.ConnPolicy = ConnPolicy2tab
now printing a ConnPolicy again calls our function and prints the desired fields:
> return rtt.Variable("ConnPolicy") {data_size=0,type="DATA",name_id="",init=false,pull=false,transport=0,lock_policy="LOCK_FREE",size=0} >
If you are used to manage your application with the classic OCL Taskbrowser or if you want your application to be connected via Corba, you may only use lua for deployment, and continue to use your former deployer. To do so, you have to load the lua service into your favorite deployer (deployer, cdeployer, deployer-corba, ...) and then call your deployment script.
Exemple : launch your prefered deployer :
cdeployer -s loadLua.ops
with loadLua.ops :
//load the lua service loadService ("Deployer","Lua") //execute your deployment file Lua.exec_file("yourLuaDeploymentFile.lua")
and with yourLuaDeploymentFile.lua containing the kind of stuff described in this Cookbook. Like the one in paragraph "How to write a deployment script"
$ <fsm_install_dir>/tools/rfsm-viz -f <your_fsm_file>.lua
options:
see here: https://gist.github.com/3957702 (thx to Ruben).
Answer: everything besides Ports and Properties. So if you have Lua components/Services which are deleted and recreated, it is advisable to cleanup properly. This means:
portX:delete() Update for toolchain-2.5: The utility function rttlib.tc_cleanup() will do this for you.
Please ask questions related to RTT Lua on the orocos-users mailing list.
Lua specific links
The RTT Lua bindings are licensed under the same license as the OROCOS RTT.