[MacRuby-devel] CNC Machine control using USB to IEEE 1284 Parallel port adapter

[Will Thorne]

Perhaps getting a bit off topic for MacRuby list now... Back when I was doing this Arduino didn't exist, I was programming Microchip PIC 16F877 chips in C, I seem to remember that when you receive an interrupt it disables more interrupts from the same source until you reset the bit in the relevant register. You can just debounce the input in software by sampling the state of the input pin a couple of times with a few ms between them then re-enable the interrupt for that port. There must be a similar mechanism for dealing with this problem on with Arduino/Atmel chips? But yeah, you can find yourself spending days trying to work out why your code stopped working, sometimes with only an LED for feedback! It's good fun working on things that do something immediate and physical though, good luck with your project,
W 

On 20 Jan 2012, at 20:51, macruby-devel-request at lists.macosforge.org wrote:

> Message: 3
> Date: Fri, 20 Jan 2012 12:43:46 -0800
> From: Rich Morin <rdm at cfcl.com>
> To: "MacRuby development discussions."
> 	<macruby-devel at lists.macosforge.org>
> Subject: [MacRuby-devel] CNC Machine control using USB to IEEE 1284
> 	Parallel	port adapter
> Message-ID: <p06230933cb3f80f6c1e1@[192.168.1.205]>
> Content-Type: text/plain; charset="us-ascii"
> 
> Using a general-purpose OS (eg, Mac OS X) for real-time
> applications is a bit of a tarpit.  So, I like the idea
> of using an Arduino (etc) for this sort of thing.
> 
> That said, there are some things that will cause problems
> even in an Arduino.  For example, taking raw input from a
> switch or button may cause the Arduino to see a bunch of
> momentary spikes as the mechanical contacts settle.
> 
> So, consider using some sort of hardware input filtering
> (eg, a one-shot or some analog filtering).  This will be
> far easier than trying to make your code handle the extra
> interrupts.
> 
> -r
> -- 
> http://www.cfcl.com/rdm            Rich Morin
> http://www.cfcl.com/rdm/resume     rdm at cfcl.com
> http://www.cfcl.com/rdm/weblog     +1 650-873-7841
> 
> Software system design, development, and documentation
> 
> 
> ------------------------------

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