Harold Hallikainen escreveu:
> I agree with you. For simplicity and cost, it really seems worthwhile to
> just use an external RTC chip. Most of them seem to be I2C, but I like SPI
> better (faster, simpler, etc.). There are some RTC "chips" that have the
> crystal and temperature compensation on board. You can really accurate
> that way.
>
> Harold
>   =


I agree with both. I like to use Maxim-Dallas' devices, but I prefer the
I2C ones because they use less I/Os and I can share the bus with other
devices without using more I/Os for chip selects.


With SPI you will need 3 I/Os plus one I/O per device in the bus. Indeed
SPI is faster (up to several Mbps) and I2C is usually 400kbps (some
devices work up to 1Mbps) but unless your PIC is using a very high clock
you won't be able to break the 400Kbps barrier with bit-banged SPI or
I2C anyway.

And on the simplicity subject, after you have a well written set of
routines to deal with the communications, the complexity/simplicity
stays hidden.

Regards,

Isaac

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