HAL mapping direction <= versus =>

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

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

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

Thanks

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.

# --- 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

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

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