> Thomas Magin wrote (of his LPT driven I2C interface):
> Why should I pay for hardware when it can be done in software alone? Elektor
 is a
> hardware magazine. Software is seen as a necessary evil. As a penny-pincher
> (professionally or personally!) I try to solve problems with the minimum of
 hardware.


It's worse than that. Elektor was stuck in some kind of time-warp; many
projects used large numbers of chips, usually, 74LS or worse, and needed
substantial power supplies. In the case of their I2C project, the
software was not very good, using a low-level IOCTL file access method
that is rather hard to use. It had bugs, so I phoned them. They replied
loftily "we do not offer upgrades to software".

I notice that W H Smiths no longer stock this magazine, and nor does the
public library. Has something happened to it?

I2C: I noticed the following announcement in a recent magazine: "Philips
announce an enhancement to its I2C that allows ICs with different supply
voltages to communucate, for minimal additional design-in effort or
cost". The remainder of the item indicates that Philips' chips now work
on 2.7 volts or less, and their "simple effective solution" for mixing
old and new chips involves a couple of transistors. The full circuit is
probably somewhere on the Philips Web Site.

Ricoh have brought out an I2C clock-calendar chip which has an
adjustable trimmer capacitor for the quartz crystal oscillator built
into the chip. It is the RS5C372A, in an 8-pin SSOP package. Power-down
current drain is 0.5 microamp at 3 volts.

I'm sure I've seen a built-in trimmer before, but I can't remember
where.

John Blackburn.