[oopic] Re: Serial communication between two oopics

RS232 is good for a couple of dozen feet (maybe less at high speed).
Beyond that you definitely want to use RS485.

Dump the R board (ok, set it aside for another project), get a second
S board and use any of the RS485 drivers from www.maxim-ic.com.

If
you organize the bus for full duplex, you can look exactly like a
serial link: the transmit of one end connects to the receive of the
other end and vice versa.

You can get the OOPic version of the MiniSumo Mark III controller from
www.junun.org for $49 (kit, "some assembly required"). Socket the
DS232 and leave it out. At this point, the 40 pin header is
compatible with the S board. You can use Mark III prototype boards to
plug in to the header and put the RS485 driver chip on these. Other
interface boards that are compatible with the S board are also
compatible with the Mark III board.

http://www.junun.org/MarkIII/Info.jsp?item=28 - controller
http://www.junun.org/MarkIII/Info.jsp?item=4 - prototype board

With Philips (now NXP) buffers, I2C is limited to about a mile. There
are lesser buffers for using I2C over a few dozen feet. Someone
around here did a project about a year ago with I2C over 30 feet or
so. Search the archives for I2C.

The good news with serial is that you can use wireless modems. I
haven't seen I2C wireless but I suppose it could be created with a
coprocessor.

Interacting over a serial port implies that there is code running on
both processors that deals with communications. Since you don't have
access to any type of interrupt and the buffer for oSerialPort is only
4 bytes, you have to deal with all of this in code and do it
frequently. You can probably use event code as a type of interrupt.

In the end, the ability of I2C to simply change object values is far
more powerful than any type of serial link. And it doesn't require
code in a loop to send/receive.

Richard

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