i would suggest u for i2c bus or rs232 intrerface using rxd and txd pins.
although with suggested scheme ur some of the wires will be left out , u can use them for future development
Reza wrote:
--- Chuck Hackett wrote:
> I would like to transfer data some distance (100
> feet in one case, 400 feet in
> another) between AVRs and I'm looking for the least
> complex, least expensive way
> to accomplish this. Environment:
>
> 1) Using facilities available on AVR processors
> (such as UART, TWI, etc.)
>
> 2) I have cable in the ground which is Telco grade,
> gel filled, direct bury
> cable with 6 twisted pair
>
> 3) Speed is not critical. Of course I'd like to go
> as fast as possible but I'm
> willing to sacrifice speed to keep complexity/cost
> down ... Well, I'd rather not
> go back to the 110 bps days! :-)
>
> 4) Multimaster is desirable
>
> I'm thinking that the solution will use some king of
> differential driver.
>
> I was doing some reading about TWI but it's unclear
> to me if this works in this
> situation. The only thing I could find about
> distance limits was that the bus
> capacitance must be below 400pf but I don't know the
> capacitance of my cable ...
>
> BTW: I think this forum is appropriate for this, if
> not, please let me know.
>
> Suggestions?
>
> Cheers,
>
> Chuck Hackett
> "Good judgment comes from experience, experience
> comes from bad judgment"
> 7.5" gauge Union Pacific Northern (4-8-4) 844
> http://www.whitetrout.net/Chuck
>
>
>
>
Hi;
as I know (using Siemens documents) if you use RS232
(using MAX232) the distance is limited to 100 feet.
but Siemens also offered some other solutions:
signalling noise-prtction dist(feet) max-speed
----------------------------------------------------
RS232 somehow 100 9600
RS485 somehow 1500 9600
RS422 good 3500 upto 19200
CurrentLoop best 3500 max of 9600
note: Siemens calls RS232 as V24, RS422 & RS485 as X27
and CurrentLoop as TTY.
in a very noisy environment the best solution is using
current loop (4, 20mA) one node in Active (current
generator) and the other in Passive (current
switcher/detector) mode.
but in steel making factory which I'm working, they
use commonly RS422(Siemens:X27) in low noise
environments, and CurrentLoop or TTY in high noise
env.
ofcouse you can make a network with these links. but
for RS422/X27 there is a limitation of 32 partners on
each link without repeater. for some applications see:
www.rs485.com
and see Texas Instruments products for RS422
interfacing.
otherwise if the environment is too noisy and you can
pay more money, there is some fiber_optic-RS232
switchs (eg: ADAM serias made by Advantech). or some
wireless equipments (upto 20miles, with a speed of
115K bps) but is very expensive.
good luck.
(and excuse me for poor english!)
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