User Manual

MPR/MIB User’s Manual
Wireless Sensor Networks
Doc. # 7430-0021-06 Rev. A Page 29
X NOTE: Programmers should be cautioned that the MICAz receiver radio stack
(CC2420RadioM.nc) will be disabled if the INT2 pin is reprogrammed/re-tasked by another TOS
component.
4. MTS300/310 (a.k.a., micasb) Temperature Sensor
• INT2 control line is used on the MTS300/310 (micasb) for enabling the
thermistor. During temperature measurement, interrupts from the MICAz radio
receiver are inhibited. MICAz radio received packets are buffered in the CC2420
RX FIFO. If the MTS300/310’s 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 MTS300/310
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.
• A Temporary Fix the Temperature Sensor Issue:
o INT2 Control
A modified PhotoTempM.nc module is provided in tinyos-
1.x/tos/platform/micaz/. This module restores INT2 port following each
measurement.
o Temperature data drop out
Software can be added to exclude/reject a temperature reading differentials
that exceed what is physically possible from one sample to the next.
o Hardware can be modified to buffer/overdrive CC2420 Radio’s packet
received flag during temperature measurements. The following two changes
are suggested.
a. MTS300/310 Sensor Board Module: Remove capacitor C1 (located near
RT1 thermistor)
b. MICAz Module: Change resistor at location R31 to 10 kΩ.