AVR-Chat

Chuck,

    I too was going to suggest RS485.   I have used the Mavric-II boards 
with great success and just finished up a project which involved using  
RS485 on these units. They include all the hardware required and come at 
a reasonable cost. Check them out at: http://www.bdmicro.com/

Brian Dean who sells these boards (and is also a member on this list) 
also has a document which describes a RS485 protocol he designed. The 
code seems to also be available. Might be worth checking out at  
http://www.bdmicro.com/code/robin/

Good luck with your project.

-james

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
>
>
>
>
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