halcmd excels in specifying components and connections but these scripts offer no computational capabilities. As a result, INI files are limited in the clarity and brevity that is possible with higher level languages.
The haltcl facility provides a means to use Tcl scripting and its features for computation, looping, branching, procedures, etc. in INI files. To use this functionality, you use the Tcl language and the extension .tcl for HAL files.
The .tcl extension is understood by the main script (linuxcnc) that processes INI files. Haltcl files are identified in the the HAL section of INI files (just like HAL files).
[HAL] HALFILE = conventional_file.hal HALFILE = tcl_based_file.tcl
With appropriate care, HAL and Tcl files can be intermixed.
1. Compatibility
The halcmd language used in HAL files has a simple syntax that is actually a subset of the more powerful general-purpose Tcl scripting language.
2. Haltcl Commands
Haltcl files use the Tcl scripting language augmented with the specific commands of the LinuxCNC hardware abstraction layer (HAL). The HAL-specific commands are:
addf, alias, delf, delsig, getp, gets ptype, stype, help, linkpp, linkps, linksp, list, loadrt, loadusr, lock, net, newsig, save, setp, sets, show, source, start, status, stop, unalias, unlinkp, unload, unloadrt, unloadusr, unlock, waitusr
Hay dos casos especiales para los comandos gets y list debido a conflictos con los comandos internos de Tcl. Para haltcl, estos comandos deben ir precedidos de la palabra clave hal:
halcmd haltcl
------ ------
gets hal gets
list hal list3. Haltcl INI-file variables
Las variables INI son accesibles tanto por halcmd como por haltcl pero con sintaxis diferente. Los archivos INI de LinuxCNC usan los especificadores SECTION y ITEM para identificar elementos de configuración:
[SECTION_A] ITEM1 = value_1 ITEM2 = value_2 ... [SECTION_B] ...
Los valores de los archivos INI son accesibles por sustituciones de texto en archivos HAL utilizando la forma:
[SECTION]ITEMLos mismos valores de archivo INI son accesibles en archivos .tcl usando la forma de una variable global de matriz Tcl:
$::SECTION(ITEM)
For example, an INI file item like:
[JOINT_0] MAX_VELOCITY = 4
is expressed as [JOINT_0]MAX_VELOCITY in HAL files for halcmd
and as $::JOINT_0(MAX_VELOCITY) in Tcl files for haltcl.
Because INI files can repeat the same ITEM in the same SECTION multiple times, $::SECTION(ITEM) is actually a Tcl list of each individual value.
When there is just one value and it is a simple value (all values that are just letters and numbers without whitespace are in this group), then it is possible to treat $::SECTION(ITEM) as though it is not a list.
When the value could contain special characters (quote characters, curly-brace characters, embedded whitespace, and other characters that have special meaning in Tcl) then it is necessary to distinguish between the list of values and the initial (and possibly only) value in the list.
In Tcl, this is written [lindex $::SECTION(ITEM) 0].
For example: given the following INI values
[HOSTMOT2] DRIVER=hm2_eth IPADDR="10.10.10.10" BOARD=7i92 CONFIG="num_encoders=0 num_pwmgens=0 num_stepgens=6"
And this loadrt command:
loadrt $::HOSTMOT2(DRIVER) board_ip=$::HOSTMOT2(IPADDR) config=$::HOSTMOT2(CONFIG)
Here is the actual command that is run:
loadrt hm2_eth board_ip={"10.10.10.10"} config={"num_encoders=0 num_pwmgens=0 num_stepgens=6"}
This fails because loadrt does not recognize the braces.
So to get the values just as entered in the INI file, re-write the loadrt line like this:
loadrt $::HOSTMOT2(DRIVER) board_ip=[lindex $::HOSTMOT2(IPADDR) 0] config=[lindex $::HOSTMOT2(CONFIG) 0]
4. Converting HAL files to Tcl files
Los archivos .hal existentes se pueden convertir en archivos .tcl mediante la edición manual para adaptar las diferencias mencionadas anteriormente. El proceso puede ser automatizado con scripts que los convierten utilizando estas sustituciones.
[SECTION]ITEM ---> $::SECTION(ITEM)
gets ---> hal gets
list ---> hal list5. Haltcl Notes
In haltcl, the value argument for the sets and setp commands is implicitly treated as an expression in the Tcl language.
# set gain to convert deg/sec to units/min for JOINT_0 radius setp scale.0.gain 6.28/360.0*$::JOINT_0(radius)*60.0
Whitespace in the bare expression is not allowed, use quotes for that:
setp scale.0.gain "6.28 / 360.0 * $::JOINT_0(radius) * 60.0"
In other contexts, such as loadrt, you must explicitly use the Tcl expr command ([expr {}]) for computational expressions.
loadrt motion base_period=[expr {500000000/$::TRAJ(MAX_PULSE_RATE)}]
6. Haltcl Examples
Consider the topic of stepgen headroom. Software stepgen runs best with an acceleration constraint that is "a bit higher" than the one used by the motion planner. So, when using halcmd files, we force INI files to have a manually calculated value.
[JOINT_0] MAXACCEL = 10.0 STEPGEN_MAXACCEL = 10.5
Con haltcl, puede usar los comandos Tcl para hacer el cálculo y eliminar el elemento STEPGEN_MAXACCEL del archivo INI por completo:
setp stepgen.0.maxaccel $::JOINT_0(MAXACCEL)*1.05
Another haltcl feature is looping and testing. For example, many simulator configurations use "core_sim.hal" or "core_sim9.hal" HAL files. These differ because of the requirement to connect more or fewer axes. The following haltcl code would work for any combination of axes in a trivkins machine.
# Create position, velocity and acceleration signals for each axis set ddt 0 for {set jnum 0} {$jnum < $::KINS(JOINTS)} {incr jnum} { # 'list pin' returns an empty list if the pin doesn't exist if {[hal list pin joint.${jnum}.motor-pos-cmd] == {}} { continue } net ${jnum}pos joint.${jnum}.motor-pos-cmd => joint.$axno.motor-pos-fb \ => ddt.$ddt.in net ${axis}vel <= ddt.$ddt.out incr ddt net ${axis}vel => ddt.$ddt.in net ${axis}acc <= ddt.$ddt.out incr ddt } puts [show sig *vel] puts [show sig *acc]
7. Haltcl Interactive
The halrun command recognizes haltcl files. With the -T option, haltcl can be run interaactively as a Tcl interpreter. This capability is useful for testing and for standalone HAL applications.
$ halrun -T haltclfile.tcl8. Haltcl Distribution Examples (sim)
The configs/sim/axis/simtcl directory includes an INI file that uses a .tcl file to demonstrate a haltcl configuration in conjunction with the usage of twopass processing. The example shows the use of Tcl procedures, looping, the use of comments and output to the terminal.