HAL Component Help

Bend
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08 Jun 2020 14:09 #170645 by Bend

HAL Component Help was created by Bend

I am using LinuxCNC to run a machine at my plant, we are using a HAL Component to run the tool changer on the machine. Unfortunately it is a fairly complex change sequence with numerous sensors and safety's in place making it difficult to design.

Personally, i am new to HAL Component programming and don't know what i can and cant do. (I have found that it wont let me do functions, or for loops).

Wondering if there is any way to do a function call that i have missed for a tool change component?

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tommylight
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08 Jun 2020 14:15 #170648 by tommylight

Replied by tommylight on topic HAL Component Help

That is not enough info to be able to help properly, but did you try the "carousel" component?
There is also classic ladder that might help, and remap.
Some pictures of the tool changer and a brief explanation of how things function or are supposed to, would be helpful.

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cmorley
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08 Jun 2020 14:20 #170650 by cmorley

Replied by cmorley on topic HAL Component Help

HAL components must cycle through each time period.
Your component can't run continuously until the tool change is finished.
This dictates writing them as state machines.
It checks what the current state is, calculates what it should be next, sets the pins to reflect that, then ends until the next time period.

Maybe you could describe the problem sequence here and we could try to suggest a solution.

Chris

The following user(s) said Thank You: tommylight, Aciera

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Bend
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08 Jun 2020 20:00 #170679 by Bend

Replied by Bend on topic HAL Component Help

The main issue that i am running into is that there are multiple places that i want to execute the same code. i.e. during a homing process i want to check that the locking pin is retracted, but i also want to do that in the tool change sequence... I was hoping to be able to write some code something like this:

...
...
...
WaitForLockingPinDisengage()
...
...
...

WaitForLockingPinDisengage(){
if (!lockingPinRetracted || lockingPinExtended){
break;
}
}

The main reason is that the locking pin for instance requires that the hydraulic pump is on, thus the WaitForLockingPinDisengage is actually this:

WaitForLockingPinDisengage(){
if(!commandHydPump == 1 || hydPumpPress <= 50){
commandHydPump = 1;
break;
}
if (!lockingPinRetracted || lockingPinExtended){
break;
}
}

Except, we have about 40 sensors that we care about all of which need to be verified in multiple places.

Thoughts?

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cmorley
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08 Jun 2020 20:15 #170683 by cmorley

Replied by cmorley on topic HAL Component Help

You can definitely use for loops in comp.
I am looking for an example of a function call.
carousel.comp defines a function but seems to never call it.

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tommylight
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08 Jun 2020 20:21 #170685 by tommylight

Replied by tommylight on topic HAL Component Help

There are plenty of components to achieve nearly anything in Linuxcnc, but as far as i can understand from your posts, the best way of handling this is writing a new component that would incorporate all the interlocks and checks required.
Here is an example of such a component for THC control on plasma cutters

component torchud "Torch Up Down";

description 
"""
torch up down by voltage calculated from encoder velocity
""";
 
license "GPLv2 or greater";

option singleton yes;

// Input Pins
pin in bit   enable         "enable up/down";
pin in float encoder_in     "connect to encoder.nn.velocity";
pin in float voltage_offset "to set 0 volts";
pin in float voltage_scale  "to set correct voltage";
pin in float setpoint       "setpoint voltage";
pin in float tolerance      "deviation from setpoint before up/down";
pin in float arc_ok_min     "min voltage to generate arc ok signal";
pin in float arc_ok_max     "max voltage to genarate arc ok signal";

// Output Pins
pin out float arc_voltage   "calculated arc voltage";
pin out bit   move_up       "arc voltage is too low";
pin out bit   move_down     "arc voltage is too high";
pin out bit   arc_ok        "signal that arc volatage is ok";

function _;

;;

#include "rtapi_math.h"

FUNCTION(_) {
    arc_voltage = (encoder_in - voltage_offset) * voltage_scale;
    if(arc_voltage < 0){arc_voltage = 0;}
    if(enable && arc_voltage > arc_ok_min && arc_voltage < arc_ok_max){
		arc_ok = 1;
	}else{
		arc_ok = 0;
	}
    if(enable && arc_voltage > setpoint + tolerance && arc_voltage > arc_ok_min && arc_voltage < arc_ok_max){
        move_down = 1;
    }else{
        move_down = 0;
    }
    if(enable && arc_voltage < setpoint - tolerance && arc_voltage > arc_ok_min && arc_voltage < arc_ok_max){
        move_up = 1;
    }else{
        move_up = 0;
    }
}

This requires the dev part of LinuxCNC installed
sudo apt-get install linuxcnc-uspace-dev
if using the userspace version of Linuxcnc, or RT-Preempt version, and subsequently
sudo halcompile --install name_of_component.comp
The setting the connections in hal file.

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cmorley
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08 Jun 2020 20:25 #170688 by cmorley

Replied by cmorley on topic HAL Component Help

I think he understands how to make a component (he said he is using a custom one), he is asking how to organize the code to work as he would like.
Maybe i'll try to make a component with function calls to see if it works.

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tommylight
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08 Jun 2020 20:42 #170691 by tommylight

Replied by tommylight on topic HAL Component Help

I thought so from his code, but was not sure.
Thank you and sorry for the confusion.

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rodw
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08 Jun 2020 21:00 #170694 by rodw

Replied by rodw on topic HAL Component Help

You can call functions but you can't call blocking functions which is what waitforlocking() seems to be.
Instead, you need to program a state machine which is essentially a switch statement on a status variable.

static int state = WAITING;
switch(state){
case WAITING:
  if(locked)
    // ask for tool change
    state = LOCKED;
  break;
case LOCKED:
  if(changed)
    state = CHANGED;
  break;
}

The attached example shows an example state machine and also a function that calculates a moving average. (It would be easy to program this by using a loop but that blocks so there is a convoluted way to calculate this without a loop)

Remember, that the servo thread is essentially a timer interrupt service routine and you cannot block an interrupt becasue all components must be serviced in that 1 millisecond between invocations. Short, sharp and sweet is the way to do this.

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Todd Zuercher
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08 Jun 2020 21:17 #170697 by Todd Zuercher

Replied by Todd Zuercher on topic HAL Component Help

Another option, if you are comfortable programming ladder logic, is to use Classicladder.

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