Lpc2000

--- In lpc2000@yahoogroups.com, "Marko Pavlin (home)" <mp@h...> wrote:
> Hello!
> 
> I would like to connect several P89LPC932 (x51 core) slaves to 
single 
> LPC2xxx master. Each slave has unused SPI and UART, which can be 
used 
> for this communication. One slave is addressed at once.
> 
> What would be best solution for that? I think SPI is ideal for 
that. I 
> could use free port pins for slave selects. Is there any other 
(more 
> scalable) option without external/additional components? How many 
slaves 
> can I connect to single master to avoid port overloading? Data 
transfer 
> rate is very low (~100 bytes/s per slave) and distance between 
master 
> and slaves is <1m.
> 
> Any further suggestions or tips&tricks?
> 
> M.

If you had CAN controllers on your devices then I'd say use that. You 
don't need all the differential stuff to run CAN, just hook up all 
the RX pins (and TX pins via diodes) and add a pull-up.

Are all these micros on one board? If so, you can use the same scheme 
as above with UARTS. That is, make a "1-wire" bus where all the rx 
lines are joined together, all tx lines are attached to the 1-wire 
through a diode, a pull-up. You just need some sort of protocol so 
that the devices don't all talk at the same time.

If they're on different boards, then RS485 is the easiest way to go 
multi-master.