Arduino Interfacing for an MPG & DRO pendant

A few months back, Jeff Epler's sample code inspired me to get off my butt and try building a really nice HMI* panel based on the Arduino. This is old hat for those on the mailing list, but I've been making good progress and currently have a (mostly) working 25-key keypad, encoder-based MPG, and LCD display prototype up and running.

I've posted a longer note on my blog which goes into a bunch of detail on how the pieces fit together. I will be posting schematics and source code as things gel a bit more. In the meantime I'm happy to answer any questions for anyone trying to get something similar working on their own.

ckcnc.wordpress.com/2010/11/20/arduino-e...ration-how-it-works/

* HMI = Human-Machine Interface, $5 word for an MPG, pendant, control panel, etc.

One critical distinction though, is that with an HMI, nothing (except an E-stop) has to be hard real-time. If I hit cycle start, and it takes 5 seconds before it starts, nothing is going to explode. In practical use, I think the messaging between the Arduino and EMC will happen up to an order of magnitude faster than the human reaction time, but it's still not truly real-time. So, no, this is *NOT* a solution for interfacing stepper motors or home switches, etc. Likewise, I have not implemented an e-stop button in here, because it wouldn't be as reliable as a hard switch. Of course, it will be pretty obvious to anyone who wants to modify it for their use, but it will be a lot harder for them to sue me if it goes badly

Thought I'd drop an update in case anyone is following this.

I posted a how-to with source code for a simpler version of this--using the Arduino to interface a switch and two LEDs. The approach used is easily extended to support dozens of digital I/Os. This page on my blog has a video and links to all the source files:

ckcnc.wordpress.com/2011/01/08/simple-emc-arduino-howto/

I also got the first batch of prototype PCBs in a few days ago, and minus a few non-fatal oversights, they appear to be all good. As this was my first time ordering my own custom PCBs, I suspect this means I will be forever cursed in the future.

ckcnc.wordpress.com/2011/01/14/pendant-pcb-take-1/

Looks good, you might be surprised how many people are following this.
You are right about the enclosure importance.

Rick G

Chugging forward slowly, but chugging! The prototype enclosure is together, and it fits, but I still need to figure out how to make the second one a lot nicer-looking. I think I have a way. Also, it's time to get back into the software to see if it can be made more stable. Right now it works fine so long as you don't give the encoder a good spin (why would you want to?).

ckcnc.wordpress.com/2011/01/23/thinking-inside-the-box/

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