net, J0Pos, stepper generator and HAL in general.
14 Jun 2019 21:35 #136915
by andypugh
Yes, that is all correct.
A HAL "Net" needs a name ( called the "signal") and then can have zero to many HAL "pins" connected to it.
Only one pin in a net can be an output (ie, one that provides a number to HAL)
There can be as many "reader" pins as you want.
In the "net" command the first term is the signal name (and that can be anything) and the the other items are HAL pins (which must exist at the point that the net command is read)
HAL isn't a program as such, it is a net-list that runs once at config time. Then all the components execute once every thread period (servo-thread or base-thread), at which point they read their inputs and write to their outputs.
Note that you can net and un-net and read and set values of pins at the halcmd prompt. If you wanted to, you could do this (with LinuxCNC not running)
You are actually unlikely to see anything as the output of ddt, though, you can't type "show pin ddt.0.out" in less that 1mS
Here are all the other HAL components:
linuxcnc.org/docs/2.7/html/
(scroll down to "Realtime components and kernel modules" (you might need to expand it)
I so this a _lot_ when debugging HAL components, it saves the complecity of interaction with the rest of LinuxCNC. Though I do spend a lot of time typing "loadusr halmeter pin ddt.0.out" (etc)
Replied by andypugh on topic net, J0Pos, stepper generator and HAL in general.
So then ddt.1.in ingests the velocity and outputs the derivative of the velocity, which is acceleration.
Is this correct?
Yes, that is all correct.
A HAL "Net" needs a name ( called the "signal") and then can have zero to many HAL "pins" connected to it.
Only one pin in a net can be an output (ie, one that provides a number to HAL)
There can be as many "reader" pins as you want.
In the "net" command the first term is the signal name (and that can be anything) and the the other items are HAL pins (which must exist at the point that the net command is read)
HAL isn't a program as such, it is a net-list that runs once at config time. Then all the components execute once every thread period (servo-thread or base-thread), at which point they read their inputs and write to their outputs.
Note that you can net and un-net and read and set values of pins at the halcmd prompt. If you wanted to, you could do this (with LinuxCNC not running)
halrun
loadrt threads
start
loadrt ddt
addf ddt.0 thread1
start
setp ddt.0.in 100
setp ddt.0.in 1000
show pin ddt.0.out
(and so on) You are actually unlikely to see anything as the output of ddt, though, you can't type "show pin ddt.0.out" in less that 1mS
Here are all the other HAL components:
linuxcnc.org/docs/2.7/html/
(scroll down to "Realtime components and kernel modules" (you might need to expand it)
I so this a _lot_ when debugging HAL components, it saves the complecity of interaction with the rest of LinuxCNC. Though I do spend a lot of time typing "loadusr halmeter pin ddt.0.out" (etc)
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