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802.15.4协议的实现

MICAZ (IEEE 802.15.4 Radio) Release Notes
03Jun04

PURPOSE
Platform support for MICAZ mote

NOTES

1. PLATFORM_MICAZ
In general this define and should be added to various applications/libraries wherever PLATFORM_MICA2
is found (eg QueueSendM.nc).

2. INT2 GPIO Line
Mica signal INT2 (Port E Pin 6 on ATMega128/) is used internally on the MICAZ for
CC2420 Receiver FIFO Ready interrupt. Use of INT2 for any other purpose must be
done with care. Specifically, the Port configuration (input, active low) must be
restored following use in other modes.

Below is a list of compatibility issues and work-arounds.

MICASB (Sensorboard) Temperature/Photo 
Background
INT2 control line is used on the MICASB (Sensorboard)for enabling the MICASB Thermistor.
-During Temperature measurement interrupts from the MICAZ radio indicating received
packet are inhibited. MICAZ Radio received packets are buffered in the CC2420
RX FIFO. If	the MICASB Thermistor is enabled for too long the receiver buffer may overflow.

-During Temperature measurements dropout in data reading. This is due to receipt of a radio
packet which will strobe the INT2 and thus affect the thermistor voltage.

-Following Temperature measurement, the MICASB driver must restore the INT2 port to 
configuration used for handling interrupts from the CC2420 radio. Symptom of not restoring
the INT2 port correctly is all that radio reception stops.

Work arounds:

-INT2 Control
A modified PhotoTempM.nc module is provided in ../platform/micaz. This module restores INT2 port
configuration for the MICAZ radio following each measurement.

-Temperature data drop out
Software can be added to exclude/discard temperature reading differentials that exceed what
is physically possible from one sample to the next. I.e. a dropout is indicated by a change
of >20C in 1 sample interval.

Hardware can be modified to buffer/override CC2420 Radio's packet received flag during 
temperature measurements. The following changes are suggested.

MICASB Module. Remove capacitor C1 (located near RT1 thermistor)
MICAZ Module. Change resistor R31 to 10KOhm.

3. ATmega128 TIMER2 Use
Timer2 is used for high resolution (32uSec) timing in the CC2420Radio stack. 
The module ../platform/micaz/HPLTimer2.nc provides the Timer2 resources to AsyncTimerJiffy
 component for this service. 

Applications using Timer2 will have to be modified to avoid conflicts with its use on the
MICAZ platform.

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