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'[PIC]:Steppers and eeprom'
2002\10\23@183939 by Goring, Steve

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Hi List ...

I am using a 16f873 controlling 3 DC motors (fwd/rev) and 2 steppers for
the pan / tilt axis of a camera.

I wish to implement a simple return to centre facility for the camera which
means saving the direction travelled and how far from the centre for each
axis.

My question is this - would these four registers best be saved in the Pic
internal eeprom or a small external I2C device.

I intend to save the registers on the completion of each move or when the
camera has reached one of the software limits set.

I have no way of knowing how far and how often the camera will be moved
as the camera is for a cctv surveillance type setup. Time is not critical
so a serial device is acceptable.

Finally, do the write/erase cycles for memory normally apply to the complete
chip or individual locations ??

Thanx


Steve




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2002\10\23@190356 by Jan-Erik Soderholm

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(About external storage to save camara position...)

I just the other day got my copy of one of the Ramtron FRAM's.
They are much like a "normal" EEPROM, but with two big differences,
they read *and* write at full speed (5 Mhz serial bus). The PIC can hardly
be to fast for it. The other thing is that Ramtron specifies 10 billion to
1 trillion write operations. That's far more then the 1 million normaly
specified for EEPROMS. At 10 billion operations , you can do 100 writes
each second during more then 3 years of continious operation.

Well, I havn't had time to plug it into my breadboard yet :-)

See : http://www.ramtron.com

Jan-Erik Svderholm
S:t Anna Data

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2002\10\24@024926 by Michael Rigby-Jones

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> -----Original Message-----
> From: Jan-Erik Soderholm [SMTP:jan-erik.soderholmspamKILLspamtelia.com]
> Sent: Thursday, October 24, 2002 12:03 AM
> To:   .....PICLISTKILLspamspam.....MITVMA.MIT.EDU
> Subject:      [PIC]:Steppers and eeprom
>
> (About external storage to save camara position...)
>
> I just the other day got my copy of one of the Ramtron FRAM's.
> They are much like a "normal" EEPROM, but with two big differences,
> they read *and* write at full speed (5 Mhz serial bus). The PIC can hardly
> be to fast for it. The other thing is that Ramtron specifies 10 billion to
> 1 trillion write operations. That's far more then the 1 million normaly
> specified for EEPROMS. At 10 billion operations , you can do 100 writes
> each second during more then 3 years of continious operation.
>
But do note that reading also "wears" out the memory, so the endurance
figure is a combined number of reads and writes.  Still, they have improved
the endurance significantly since I last looked at them.

Regards

Mike

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2002\10\24@075008 by Olin Lathrop

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> I am using a 16f873 controlling 3 DC motors (fwd/rev) and 2 steppers for
> the pan / tilt axis of a camera.
>
> I wish to implement a simple return to centre facility for the camera
which
{Quote hidden}

How often is the camera power shut down?  How much warning is there when
that happens.  Assuming a power down is infrequent, do you really need to
remember the camera position on power up?  Couldn't you just recalibrate by
finding a limit in each direction?  Wouldn't you want to do this anyway on
power up because something may have been moved externally?  If so, then why
do you need to save values in EEPROM at all instead of just in RAM?


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