rebinding keys to functions

perryh at perryh at
Tue Sep 15 08:11:35 UTC 2009

Roland Smith <rsmith at> wrote:
> Writing a driver to detect if headphones are connected sounds
> much more complicated to me than connecting a couple of switches!
> I mean, you'd have to measure something like the impedance of
> the jack. Surely that is more expensive than a simple switch?

Or use a simpler jack, with one switch that connects to ground or
not depending on whether the plug is inserted or not.  It probably
costs a cent or two less than the usual two-switch variety, and this
is a BOM (Bill Of Materials, i.e. per-unit-built) savings.  Writing
the driver is an NRE (non-recurring engineering) expense which can
be amortized over -- the manufacturer hopes -- a huge number of
delivered units.

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