Silly Questions - HAL, Arduino

Realtime is required for (software) step generation, encoder feedback, or other high speed communication. My understanding is that realtime halts any other process and dedicates all system resources to the realtime process until it completes, it isn't just about speed but about safety as well, you wouldn't want an incoming email to cause a servo to run away.

As long as you aren't trying to connect your stepper or servo drives to the arduino you should be okay for general IO, but I have to wonder what advantage you see in using an arduino over a parallel port.

kornphlake79 wrote: Realtime is required for (software) step generation, encoder feedback, or other high speed communication. My understanding is that realtime halts any other process and dedicates all system resources to the realtime process until it completes, it isn't just about speed but about safety as well, you wouldn't want an incoming email to cause a servo to run away.

As long as you aren't trying to connect your stepper or servo drives to the arduino you should be okay for general IO, but I have to wonder what advantage you see in using an arduino over a parallel port.

That makes sense now.

In that case I would have to think about how I'll connect as I want the ability to jog axis. USB doesn't seem like the best option.

You can certainly use usb for jogging.

Rick G

Using an Arduino for the HMI interface is certainly no worse than using a keyboard and mouse, and is probably much better than clicking GUI buttons. Clicking a GUI button with a USB mouse puts two non-realtime stages in the loop.

Personally, since i realised this, I prefer to do all machine-movement interaction through realtime-interface IO.

If you want to make an Arduino-empowered HMI, then look here: emergent.unpythonic.net/01198594294

There is a realtime-interfaced device for much the same money, but it is only usable if you have Mesa hardware.

I am struggling to see what the Arduino can add to the LCNC environment with the plethora of hardware options available from Mesa et al.

To me, it makes no sense to use one to just add some inputs and outputs, you should be making it do something with its CPU. Maybe return a temperature or something like that.

The Arduino is real time when correctly programmed. It is trivial to implement basic step and direction in a few lines of code, and GRBL and TinyG use the Arduino platform to do what LinuxCNC does.

It is easy to add interrupt driven step and direction to an Arduino that can run at say 10,000+ Hz which is more than enough to saturate a basic stepper motor. (I did this in 150 lines of code). With a bit more effort you can add accellaration and decellaration algorithims in the pulse stream. I did all of this for a rotary table controller which Scott in Canada used to add an indexing function to a 3 axis mill that had no support for a 4th axis. What he did was replace the push button to index the rotary table with a proximity switch. So whenever he wanted to get the table to index his part, he simply moved the tool past the proximity sensor in his G code. Very clever!

www.homemodelenginemachinist.com/showthread.php?t=24719

My code is available for download on the above forum. All config settings are stored in EEPROM so there is no need to edit the code. If you are interested, let me know as it would be great to get it on github and I don't know how to do that.

So forget using the Arduino for simple I/O, make it do something smart like Scott and I did!

Hi @all,
i'm a newbie in LinuxCNC, i jog my Axis with a USB Game Controller like this.
www.amazon.de/Gamepad-Vibration-Controll...=usb+game+controller

Simple integreated like this:
launchpad.net/~falk-t-j/+archive/ubuntu/games/+build/1737977

Works great on Wheezy with 2.7.7

i hope i don't missunderstood this Thread. Otherwise delete please

Greetings