AVR-Chat

Hi Stuart

You can use RS485 with the uart and same protocol as RS232.
You only need 1 extra pin for enable.
2-wire(twisted pair) + com, smaller chip (8pin), I recomend SN75LBC184 from 
Texas
(allows 128 devices on the bus), cheep, under 0.5US.
http://focus.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=sn65lbc184&fileType=pdf

Svenn


>
> I am designing up a system where a single master AVR has to talk to a
> heap of Slave AVR's.
>
> In my previous efforts the slaves have always been on the same PCB, so I
> have been used SPI.
>
> Now the slaves are going to be on different PCB's, which comms cables
> running between them.
>
> The run length would be about a meter, maybe two meters.
>
> I recall seeing people say that SPI should 'leave the board'.
>
> I have used rs232 in the past, but it means either:
>
> 1) Creating a serial communications ring where Master talks to slave 1,
> slave 1 talks to slave 2 and slave 2 talks to the master. If one of the
> slaves die, its hard to tell which is at fault.
> 2) Having a master device that has multiple rs232 uarts.
>
> So my questions are these: Is there a better bus to use than rs232?
> Are there any Mega's or other chips I can use to get multiple rs232
> uarts?
> Can you run 4 or 5 rs232 buses on say a mega8 or mega16 by using bit
> banging?
>
> The development time for this is short, so I am not sure I can wait for
> the AVR CAN's chip to show up.
>
> Any info or tips would be appreciated!
>
> Kind Regards,
> Stuart Whelan
>
> Recursion: See Recursion.
>
>
>
> Yahoo! Groups Links
>
>
>
>