Re: [avrdude-dev] How to add I2C device disable preamble?

[Bob Paddock]

> Ok this is farfetched (caveat: I am only a software jockey), but can the
> board detect when the ISP programmer is plugged in? If so, can that be  
> used to switch off power to the accelerometer chip only?

Removing power from the accelerometer doesn't guarantee
that the chip will shut down.  As there would still
be activity on its pins, it could be powered
via energy going from the pins through the ESD
protection diodes.

Passing current via the ESD diodes is always
to be avoided in a design, as they
are not designed for the power application,
they could be damaged, leading to a latent
defect that becomes a real failure
when some ESD does show up.

It is these kinds of 'sneak paths'
that can make designing of low power and/or
mutil-supply circuits far more of a challenge
than its looks.

In the past I have used the 10-pin ISP
connector to do exactly what you propose.
Plugging in the ISP cable changed
the state of a multiplexer.  Alas
I don't have the space for that in
this design, unless someone has a zero space
way to implement it?