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> The bit I like best is where they count the number of bytes they received
> before they turned off the receiver and then adjust the wake-up time they
> program into the hardware, on the basis that the heat from running the
> receiver will have made the crystal run at a different speed for the next
> 1.28 seconds they're asleep, and you don't want to wake up too soon or too
> late. :-) Scary stuff going on inside there.
I know, I used to work supplying the displays for phones, and every last
tiny bit of power reduction was always demanded. For standby mode (when you
haven't touched any keys for a minute or so) we ended up with reducing the
display to just a few horizontal lines (enough to show the time and a few
icons), reducing to 3-bit colour (ie each RGB sub-pixel either fully on or
off) and reducing to 5 Hz refresh. Then you can design the power supply and
driving circuits in a clever way so that in standby you only need a fraction
of the electronics running. Because production volumes are so high there is
plenty of cash around for developing really clever and complex stuff to save
power and improve performance.
> I also found out that while my car has a bluetooth headset feature built
> in that lets me make hands-free calls from the car without taking the
> phone out of my pocket, lots of cars in Europe use the "SIM profile" of
> bluetooth. So there's an entire phone built into the car that just
> wirelessly accesses the SIM chip, pulling in the phone book of whoever is
> in the car and everything. Very cool.
Oh yes, my current car and my last car had that. It means when someone
calls you the car can display the name of the person from the phonebook.
Note that the phonebook in most phones is stored in the phone and not on the
SIM card, because the SIM card has very limited storage capacity. Also it
means if you want to call someone you can scroll through the address book on
the car display and not have to use the tiny buttons and screen on your
phone whilst driving.
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