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'RS485 Protocol using PIC microcontrollers'
1998\06\19@131613 by adrian aslett

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<DIV><FONT color=#000000 size=2>I am looking for information or coding using the
RS485 protocol.</FONT></DIV>
<DIV><FONT color=#000000 size=2></FONT>&nbsp;</DIV>
<DIV><FONT color=#000000 size=2>Can anyone provide me with information on
this.</FONT></DIV>
<DIV><FONT color=#000000 size=2></FONT>&nbsp;</DIV>
<DIV><FONT color=#000000 size=2>Your assistance is
appreciated.</FONT></DIV></BODY></HTML>

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1998\06\19@171608 by Frank Tamminga

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adrian aslett wrote:
>
> I am looking for information or coding using the RS485 protocol.
>
> Can anyone provide me with information on this.

I am sorry to disappoint you, but RS485 is not a protocol. It is the
physical layer, such as RS232, RS422, optical cabling, coax.

RS485 is a way for serial communications on a two wire cable, where
shielding is not (or less) necessery.

The devices use a method of transmitting data that is highly insensitive
for external interference like magnetic fields.

For implementing RS485 within a PIC project, you'll have to know that
RS485 uses an external component like a SN75LBC179 for the job. You
cannot 'emulate' it with the PIC.

The question now is, does the RS485 bus one or more transmitters. If you
use just one transmitter, the job is easy. Set one transceiver (that's
what they're named) to Send, and the other to receive. Done.
If you have more tranmitting devices on the same set of wires, it gets
more complicated. You'll have to watch the state of the 'bus' to avoid
data collisions. If you want more explanation of this, let me hear.


CU,   Frank  (spam_OUTp.f.tammingaTakeThisOuTspamhgt.nl)

1998\06\19@171620 by Andy Kunz

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At 05:25 PM 6/19/98 +0100, you wrote:
>    I am looking for information or coding using the  RS485 protocol.   Can
>anyone provide me with information on  this.   Your assistance is
>appreciated.


485 is a hardware definition, not a software one.

Best bet is a polling algorithm for speed of implementation.

Andy

==================================================================
Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
==================================================================

1998\06\20@080448 by Frans Gunawan

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----------
> From: adrian aslett <.....adrianKILLspamspam@spam@TTSLTD.FORCE9.CO.UK>
> To: PICLISTspamKILLspamMITVMA.MIT.EDU
> Subject: RS485 Protocol using PIC microcontrollers
> Date: Friday, June 19, 1998 11:25 PM
>
> I am looking for information or coding using the RS485 protocol.
>
> Can anyone provide me with information on this.
>
> Your assistance is appreciated.

you may take a look at my project, I use RS485 with HC11, 8051 and PIC.
schematics and code are provided.
http://www.poboxes.com/f
goodluck

1998\06\22@073928 by Pavel Korensky

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At 17:25 19.6.1998 +0100, you wrote:
>
> I am looking for information or coding using the RS485 protocol.
> Ê
> Can anyone provide me with information on this.
> Ê
> Your assistance is appreciated.


Huh ?

Maybe I am completely wrong, but I was almost sure that RS-485 is a definition
of electrical characteristics of the interface. AFAIK, RS-485 doesn't contain
any description of higher level protocol.

I am using normal RS-232 routines for communication over RS-485 interface
(LT491 chip). I implemented small set of routines (called HomeBus :-))) for
several communications in my home. Every house automation point has a PIC
which
is connected to RS-485 via 491 chip. I am using two pairs, so full-duples is
possible. To avoid collision detection and similar, I am using simple
solution,
which is probably well known. Master is using one pair for sending the packet.
The first byte of the packet is the address of the device. Every device has a
unique address. The slaves are responding on the other pair of wires. Slave to
slave communication is also possible, but only via master. I am using similar
principle as the old Arcnet networks - token passing on logical circle.
Works like a charm (hmm, almost :-)

PavelK

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1998\06\30@112338 by Alex Torres

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> I am looking for information or coding using the RS485 protocol.
> Can anyone provide me with information on this.
> Your assistance is appreciated.

RS485 is not a protocol, it is only harware specific. Protocol you must
choos youself.

==================================
Alex Torres, Kharkov, Ukraine (exUSSR)
E-Mail: .....altorKILLspamspam.....geocities.com
2:461/28 FidoNet
Home Page: http://www.geocities.com/SiliconValley/Lab/6311

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