conditional postgui.hal

Hi all,
I have an usb pendant which is not always plugged in.
Is it possible to include its hal-file depending on whether the pendant is plugged in or not.

Thanks,
vph

Not built in to HAL but one could write a python HAL component that would check for the pendant pins and connect the pins accordingly.

I have often thought this would be a good feature to have but never got to the point of building it.

Chris M

Thank you Chris!

I already started making a hal component doing that but wanted to make sure it doesn't already exist and not wasting time.

Best Regards,
Filip A.

If you are using python and the hal module..
note there are undocumented functions that would help:

component_exists()
component_is_ready()
connect()
new_sig( signal_name,type )
set_p()


Chris M

So I went ahead and created a python program that optionally loads commands.
This is of course only one way it could be done.
Here is the program:
This I saved as try_loader and made it executable.
In my custom_postgui.hal file I added:
loadusr -w try_loader

I then added two other HAL file to my config:

try_options.hal
Which has the single command to load my USB joystick:
try_success.hal
Which connects the joystick to halui:
If I have a joystick connected it allows it to jog my X axis.
If I do not I will get a little bit of noise in the terminal (if it is showing):

No input devices could be opened. This usually indicates a misconfigured
system. Please read the section 'PERMISSIONS AND UDEV' in the hal_input
manpage
try_options.hal:1: waitpid failed hal_input hal_input
try_options.hal:1: hal_input exited without becoming ready
**** TRY LOADER Info: Optional equipment not connected ****
but the config continues to load with no problems.

The try_loader program tries to load the first HAL file and if it succeeds, it will load the second file.
If the second file has errors it will stop the config and display the errors.
If the first HAL file doesn't succeeded, then it doesn't try to load the second and just carried on.

Hope that helps someone.
Chris M

Thanks a lot Chris! That was fast. For my purposes I was thinking to just check if the serial port is created and then load the rest. But your way is much better and more complete.

Regards,
Filip A.