On Thu, 2007-09-20 at 23:00 -0400, jim ruxton wrote:
> Hi I have some pic to pic communication I have to do, does anyone know
> if there is a summary of these two protocols that would help me to
> determine which of the two I should use. The communications doesn't have
> to be fast and is only between 2 pics so I really just want to use the
> simplest protocol to implement, I'll also be using the UART so hopefully
> there won't be any conflicts.

If you're using the I2C/SPI hardware in the PICs it's pretty much a wash
from a software point of view. I much prefer I2C. While it's a little
more complicated to use, it only uses 2 wires, and there is basically
only one config.

SPI SHOULD be simple, but the fact that it has 4 different configs
(clock polarity and which edge data changes) really turns it into 4
different standards. I've been burned many times with datasheets either
not specifying which polarity/clock edge they need, or conflict on what
they need. 

Also, some devices have different requirements for going to "idle", some
need extra clock cycles thrown in after a transaction for no good reason
(SD cards), for something that should be a standard, it's a mess.

OTOH I2C is MUCH tighter on what can happen on the bus, so it's alot
easier to get two devices talking.

Yes, in your case, you're controlling everything, so the SPI
"annoyances" I describe aren't really an issue for you, so what you're
seeing here is my personal bias!

TTYL

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