[TriLUG] C linux programming question

[Jim Ray]

> -----Original Message-----
> From: karl thiele [mailto:karlthiele at nc.rr.com] 
> Sent: Saturday, May 24, 2003 11:45 PM
> To: trilug at trilug.org; gregbrown at mindspring.com
> Subject: Re: [TriLUG] C linux programming question
> 
> 
> Is it possible? yes. Done it from application and kernel space. Hey 
> folks these all are interesting answers but there are devices 
> just for 
> this type of work called PLCs that work in many voltages and 
> amps.

Way overkill.

> I bet this would not take long to actually build a 
> hardware device. 

If anyone is so inclined, I will barter for a six pack of good beer if
you help me drink 'em a development system for the Motorola 68HC705C8
microcontroller with UV lamp, a dozen devices, manuals, ya da ya da ya
da.

The system is new in the box.  I bought it for a specific project that
turned out to be too much of a pain in the arse to develop.  It actually
bolts up to a EIA-232 on a PC so you can download Motorola S records to
your target system.

Then, you can use a separate device with i/o pins dedicated to
monitoring the state of ignition on/off/whatever.

The inherent design flaw in using EIA-232 is that the bit stream is not
the functional equivalent an i/o pin on a microcontroller.  I could help
with the assembly language yet know there's also a compiler used to
write in C and create the assembly language.

> I can see we have no 
> electrial 
> engineers in this discussion. 

Prolly right.  I happened to be an electrical engineer in a past life,
though, and currently go by the title eclectical engineer.

> 
> Greg Brown wrote:
> 
> > Hey all.  Is it possible, using C, to monitor voltage on 
> one pin of a
> > serial port when voltage is supplied from an outside source or do I 
> > have to knuckle under and learn some assembly for this 
> task?  What I'm 
> > after here is with an embedded linux machine mounted in a car and I 
> > want to have power supplied by an always-on supply in the car.  I'd 
> > also like to have a pin on a serial port connected to a 
> "only on when 
> > running" wire (somehow).  So when the voltage drops to zero on the 
> > "only on when running" pin the embedded device will shut 
> itself down 
> > automatically (the device would be turned on manually via an "on" 
> > button).
> >
> > Is this theoretically possible using C?
> >
> > Greg