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exartemarte
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Pi are fun

Fri Jul 27, 2012 3:59 pm

We still see the occasional disappointed post from those who expected a games machine cum home cinema for £25, so I thought I'd mention the fun I'm having with mine – on something probably closer to what Eben has in mind when he talks about "physical computing".

I'm resurrecting a venerable robot arm that has been gathering dust under my bench for far too long.

Image

There's more to it than you might imagine. The thing has no on-board processing power – it presents an 8-bit parallel interface through which you control (once you've sorted out the connections and the protocol) each individual coil in each of six 4-pole stepper motors. All the stepper sequencing, timing, etc has to be done in software on the Pi. I'm using C, with Gordon's wiringPi. And I confess I used an easily replaced Arduino to sort out the connections and make sure the arm was safe, before connecting it to my Pi.

You can't actually see the Pi in the picture: it's in a black (Lego) case under the right hand side of the monitor, next to its usb hard drive (the tall black box with a blue light on the front). It has neither keyboard nor display (what I believe they call "headless" around here), just the hard drive, wired Ethernet and the gpio cable. It's running Raspbian, with ssh enabled and Samba installed.

I think the arrangement gives me the best of both worlds. In side-by-side windows on the PC, I can use my preferred PC software to edit and manage the files stored on the Pi's hard drive, and I can access the Pi's command line in PuTTY to compile and execute them. It's a happy meeting of technologies, combining the ease of use and familiarity of the PC with the programmability and i/o capability of the Pi – not forgetting the networking technology that makes it all possible.

There really is a flavour of the old days to all this – I was ahead of Eben, cutting my teeth on a Nascom – but of course the Foundation's project wasn't aimed at geriatrics like me. I'm sure there are plenty of youngsters out there – the next generation of engineers – who will find this sort of stuff just as fascinating, and as much fun, as I do. Provided they get the chance.

There's s short sequence showing the arm moving about a bit under Pi control here.

twocvbloke
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Re: Pi are fun

Sun Jul 29, 2012 10:18 am

That's a pretty neat setup and a great idea for the Pi, just shows how multi-functional the Pi is, being able to operate that arm that was never designed for the Pi, that's what I like about proper engineering, putting things that weren't meant for one another together and getting them to work, just to see what happens... :mrgreen:

All it needs now is an autonomous wheeled platform, a blue paintjob, and you could call it Bob the Scutter... :lol:

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exartemarte
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Re: Pi are fun

Tue Jul 31, 2012 12:31 am

twocvbloke wrote:All it needs now is an autonomous wheeled platform, a blue paintjob, and you could call it Bob the Scutter... :lol:
I think someone else on here is already working on that:
http://www.raspberrypi.org/phpBB3/viewtopic.php?t=5233

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AndrewS
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Re: Pi are fun

Tue Jul 31, 2012 1:25 am

twocvbloke wrote:All it needs now is an autonomous wheeled platform, ...
Liz will ask you to add a sandwich as well ;)

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