Depending on cost and complexity limits, I would go with a CAN solution.
It'll go the distance, be fast, differential, handle collisions, be
asynchronous, provide interrupts, extremely versatile.  Several 18
series PICs have a controller built in, all you need is the transceiver
which is a simple 8-pin part.  There's also an SPI CAN controller from
Microchip, the MCP2510 which is easy to use as well.

nick@veys.com / www.veys.com

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Andreas Doktar
> Sent: Saturday, January 18, 2003 11:08 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [EE]: PIC to PIC communication
>
>
> I'm having this design problem:
>
> I have a couple of PIC16F84:s that have to communicate with
> each other. I'm going to use some kind of asyncronous serial
> protocol. But when the PIC:s are about 50 meters from each
> other, what is the smartest way to connect them?
>
> Alt I
> The simplest way would be to just connect e.g. RB0 on all
> PIC:s to the same wire and hop there will not be any kind of
> interference.
>
> Alt II
> Use some kind of transistor to rise the voltage to about 12 V
> and a diod and a zener to level the signal back to 5 V. I
> tried to illustrate this in a fast drawn schematic.
http://www.abo.fi/~adoktar/alt2.gif

Alt III
Some kind of bi-directional buffer. Which part would be suitable?

Thanks for your answers, regards,
Andreas Doktar

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