>
> I'm putting together a battery powered PIC-based RF transmitter.  It will
> be in sleep most of the time, waking up on PORTB change, transmitting some
> data, then sleeping again.  I'm keen to keep power consumption down as low
> as possible.
>
> Obviously I need a pull-up or pull-down on the appropriate PORTB pin, but
> I'm not sure how high a value resistor I can get away with or if there are
> any benefits in pulling the pin up or down... or even how much extra
> current a single built-in pullup will add to my current power consumption
> (which will be a couple of uA in sleep).
>
> Any suggestions?
>
> Nigel
>
you might try powering the pullups through a pin on the
pic if the current isn't too high, then the pic can cut the power to
the resistors when its asleep so they only load the battery when the
transmitter's running.  ive found pullups work better than pulldowns.
Stupid way to use pic as ammeter:  when current on a pin exceeds
about 20 ma, the (16c84) just quits working.  so just rearrange the
power leads on the various peripheral chips/pullups in various
combinations that dont overload any one pin on the pic.