HAL mapping direction <= versus =>

Hello,

new to LINUXCNC HAL my brain is twisted by the meaning of <= versus =>. I thought it was data flow orientated like hardware input pin => hal input pin and reciprocally for output. And this, despite i was reading cases in contradiction with my pseudo rule...

Reading the 1986 Maho retrofit, i fell on andypugh's following post that finished to puzzle me :

andypugh wrote: The 7i77.0.0.input-NN pins are HAL _outputs_ They are physical inputs that set the value of attached HAL pins.

So the mapping needs to be maho_panel.out => 7i77.out and maho_panel.in => 7i77.in

:dry:

Andy can you help with some reference or a good explanation ?

Thanks

JC10 wrote: Hello,

new to LINUXCNC HAL my brain is twisted by the meaning of <= versus =>. I thought it was data flow orientated like hardware input pin => hal input pin and reciprocally for output. And this, spite i was reading cases in contradiction with my pseudo rule...

Reading the 1986 Maho retrofit, i felt on andypugh's following post that finished to puzzle me :

andypugh wrote: The 7i77.0.0.input-NN pins are HAL _outputs_ They are physical inputs that set the value of attached HAL pins.

So the mapping needs to be maho_panel.out => 7i77.out and maho_panel.in => 7i77.in

:dry:

Andy can you help with some reference or a good explanation ?

Thanks

As far as I know, the <=, => are just visual representation on which way the signal is being connected. You don't need to use them. I don't use them in my files.

The <= versus => don't mean anything and are not needed in the file. They can be ambiguous and confusing. They are put in so that the human can have an idea which way the data flows. I am a novice as well so no doubt others will chime in.

They are really not necessary but useful if used consistently. I refer to always define a signal on one line and send it somewhere on another line.

This where multiple sigals are set on one line, I find confusing and don't do it any more

Seems to be pretty clear in the documents...

linuxcnc.org/docs/2.7/html/hal/basic-hal.html#_net

JT

JC10 wrote:

andypugh wrote: So the mapping needs to be maho_panel.out => 7i77.out and maho_panel.in => 7i77.in

Andy can you help with some reference or a good explanation ?

This is because the HAL pin that drives a hardware output is a HAL input pin. You pass a value _in_ to the HAL pin and that controls the voltage output.

rodw wrote: They are really not necessary but useful if used consistently. I refer to always define a signal on one line and send it somewhere on another line.

Code:

# --- EXTERNAL ESTOP SWITCH --- net external-estop <= hm2_7i76e.0.7i76.0.0.input-00 net external-estop => estop-latch.0.fault-in

This where multiple sigals are set on one line, I find confusing and don't do it any more

Code:

net pause-on toggle2nist.0.is-on <= and2.0.in1 <= and2.3.in1 <= and2.5.in1 <= halui.program.is-paused

This last one is really puzzling but I did my homework and I think i am fluent with this new language to translate it in :


With this way, i see the flow of data clearly.

What is weird to me is that in yours, you only used <= arrows ?

Basic you load a NET / Signal with a pinstate
and then you can asign the signal to a outsource that takes it PYVCP led Motion control Halui .....

JC10 wrote: This last one is really puzzling but I did my homework and I think i am fluent with this new language to translate it in :

Code:

net pause-on <= toggle2nist.0.is-on net pause-on => and2.0.in1 net pause-on => and2.3.in1 net pause-on => and2.5.in1 net pause-on => halui.program.is-paused

With this way, i see the flow of data clearly.

Well, actually: Because the halui pin is an output and is the driver for the net and toggle2nist.is-on is an input:
linuxcnc.org/docs/devel/html/man/man9/toggle2nist.9.html

I have to say I think that line was contributed by Todd so It might be best to get him to correct your work as it so long I have forgotten what it does. toggle2nist.0.is-on is an input and halui.program.is-paused is an output so I think its more like:

So in this particular case the one liner is quite efficient!