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PICList Thread
'HELP! PIC Automotive application'
1998\02\17@130408 by Rawle Watson

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Hi Picpros,

I'm using the PIC16f84 in an automotive application. Basically, its an alarm
and an anti-theft device. The alarm monitors the doors, trunk and the hood
of the vehicle when the ignition is turned off. Whereas, the antitheft
device monitors it continually.

The most significant feature of this project is a bypass that gives the user
the option of setting a bypass word. This word is used for two things;

1. To reset the system in the event the vehicle was tampered with.

2. To impliment a bypass of the system in the event that the vehicle must be
sent    to the mechanic.


My problem is that the contents of the registers which contain the bypass
word is lost whenever the vehicle's battery power is removed then replaced.
Obviously, this would defeat the purpose of the system.

As I see it, the way out of this to have a back-up battery on board, or on
the other hand to use some form of memory device. However don't have the
knowledge in none of the above. I'm therefore asking your assistance.

Thanks in advance.

Rawle
Bye,
Rawle.

1998\02\17@143835 by Rick Dickinson

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At 01:16 PM 2/17/98 -0400, Rawle Watson wrote:
>Hi Picpros,
>
>I'm using the PIC16f84 in an automotive application. Basically, its an alarm
>and an anti-theft device. The alarm monitors the doors, trunk and the hood
>of the vehicle when the ignition is turned off. Whereas, the antitheft
>device monitors it continually.

[snip]

>My problem is that the contents of the registers which contain the bypass
>word is lost whenever the vehicle's battery power is removed then replaced.
>Obviously, this would defeat the purpose of the system.
>
>As I see it, the way out of this to have a back-up battery on board, or on
>the other hand to use some form of memory device. However don't have the
>knowledge in none of the above. I'm therefore asking your assistance.

Rawle,

Instead of storing the bypass word in the PIC's RAM area (file registers),
store it in the PIC's EEPROM.  Read a copy of it into RAM in your
initialization routine, so it's easier do work with, and write the new
value to EEPROM whenever it is set by the user.

- Rick "Non-volatile" Dickinson

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1998\02\17@144312 by Mike Keitz

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On Tue, 17 Feb 1998 13:16:03 -0400 Rawle Watson <.....rawleKILLspamspam@spam@SOLUTIONS2000.NET>
writes:

>
>My problem is that the contents of the registers which contain the
>bypass
>word is lost whenever the vehicle's battery power is removed then
>replaced.

Store the "bypass word" in the data EEPROM section of the chip, not the
file registers.  This is really an on-chip periperal (that only the X84
chips have) rather than an area of memory.  Data can't be accessed as
easily, and writing is very slow.  But, the data EEPROM is intended to
preserve data while power is off and it usually does.  The file registers
are ordinary static RAM and the data in them is lost when the power is
off.

A good car alarm should have its own reserve source of power, as many
crooks will cut a battery cable to disable the alarm before tampering
with the car.  This doesn't address the major limitation of car alarms:
nobody cares (other than the car's owner) when the alarm goes off.


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1998\02\17@160407 by John Payson

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> A good car alarm should have its own reserve source of power, as many
> crooks will cut a battery cable to disable the alarm before tampering
> with the car.  This doesn't address the major limitation of car alarms:
> nobody cares (other than the car's owner) when the alarm goes off.

On the other hand, this may be a definite advantage of a DIY system; you
won't have to use that chip that sounds EXACTLY like every other single
car alarm on the planet (just about all of them sound like:

Dyeeeww dyeeeww dyeeeww dyeeeww
Braaaaaohwp braaaaohwp braaaaohwp braaaaohwp
Mehhhhp mehhhhp mehhhhp mehhhhp
Ooooo eeeee ooooo eeeee ooooo eeeee ooooo eeee

[actually, I think I got the sequence not quite right there, but for what-
ever reason all the car alarm vendors seem to use the same noisemaker chip.]

1998\02\17@162250 by Roger Books

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> > A good car alarm should have its own reserve source of power, as many
> > crooks will cut a battery cable to disable the alarm before tampering
> > with the car.  This doesn't address the major limitation of car alarms:
> > nobody cares (other than the car's owner) when the alarm goes off.
>
> On the other hand, this may be a definite advantage of a DIY system; you
> won't have to use that chip that sounds EXACTLY like every other single
> car alarm on the planet (just about all of them sound like:
>
> Dyeeeww dyeeeww dyeeeww dyeeeww
> Braaaaaohwp braaaaohwp braaaaohwp braaaaohwp
> Mehhhhp mehhhhp mehhhhp mehhhhp
> Ooooo eeeee ooooo eeeee ooooo eeeee ooooo eeee
>

Voice?

Activating Auto Tracking System.
Deactivating Stereo.
Transferring digital pictures offsite.


Actually, this kind of fits in with my cell-phone idea.  Put a GPS in
it and a second number you dial with your modem to find its location.

<Politicly incorrect>

Give it to your teenage daughter.  Since I have never seen a teenager
put down a cell-phone you can now locate her any time.

</Politicly incorrect>

Roger

1998\02\17@215011 by )

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Roger Books Wrote:

> Voice?
>
> Activating Auto Tracking System.
> Deactivating Stereo.
> Transferring digital pictures offsite.
>
>
Better idea.....

How About?

("Pleasant and Calm" Voice)

"Detonator Activated...."
"Commencing Self-Destruct Sequence......"
"State Deactivation Authorization Code (Incorrect Code Will Cause
Immediate Detonation....)"
"Ten...Nine....Eight....Seven..."

-Frank ;-)

1998\02\17@235548 by tjaart

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John Payson wrote:

> > A good car alarm should have its own reserve source of power, as many
> > crooks will cut a battery cable to disable the alarm before tampering
> > with the car.  This doesn't address the major limitation of car alarms:
> > nobody cares (other than the car's owner) when the alarm goes off.
>
> On the other hand, this may be a definite advantage of a DIY system; you
> won't have to use that chip that sounds EXACTLY like every other single
> car alarm on the planet (just about all of them sound like:
>
> Dyeeeww dyeeeww dyeeeww dyeeeww
> Braaaaaohwp braaaaohwp braaaaohwp braaaaohwp
> Mehhhhp mehhhhp mehhhhp mehhhhp
> Ooooo eeeee ooooo eeeee ooooo eeeee ooooo eeee

I think I pulled a lip muscle trying to figure out what these sound like!Maybe
if you do a Dooo Beee Dooo Beee Dooo Beee Dooo Beee,
everyone will look out their windows to see if it is really 'ol Blue Eyes
himself!

--
Friendly Regards

Tjaart van der Walt
tjaartspamKILLspamwasp.co.za
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|       R&D Engineer : GSM peripheral services development    |
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1998\02\18@003058 by Todd Erickson

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John Payson wrote:

(just about all of them sound like:
>
> Dyeeeww dyeeeww dyeeeww dyeeeww
> Braaaaaohwp braaaaohwp braaaaohwp braaaaohwp
> Mehhhhp mehhhhp mehhhhp mehhhhp
> Ooooo eeeee ooooo eeeee ooooo eeeee ooooo eeee

What an accurate description!  That's just how they sound!
Could I get that in .wav?

Todd

1998\02\18@080103 by Nuno Filipe Pedrosa

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 Doesn't the PIC16F84 have E2PROM memory? I know the 16C84 has. If it
does, you could use those registers to store the bypass code.

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