User Manual

MPR/MIB User’s Manual
Wireless Sensor Networks
Doc. # 7430-0021-06 Rev. A Page 28
Power Register (code) MICAz TX RF Power (dBm)
31 0
27 -1
23 -3
19 -5
15 -7
11 -10
7 -15
3 -25
The RF received signal strength indication (RSSI) is read directly from the CC2420 Radio. In
TinyOS the RSSI is automatically returned in the TOSMsg->strength field with every radio
packet received. Typical RSSI values for a given RF input level are shown in Figure 7-1 below.
Figure 7-2. Typical RSSI value versus input RF level in dBm.
7.2.3 Known MICAz and TinyOS Compatibility Issues
1. #define PLATFORM_MICAZ
In general this #define should be added to various applications/libraries wherever
the text PLATFORM_MICA2 is found.
2. ATMega128L Timer2 Use
Timer2 is used for high resolution (32uSec) timing in the CC2420Radio stack. The
module HPLTimer2.nc located under the tinyos-1.x/tos/platform/micaz/ directory
provides the Timer2 resources to AsyncTimerJiffy component for this service.
Applications that use Timer2 will have to be modified to avoid conflicts with its use
for the MICAz platform radio stack.
3. INT2 GPIO Line
MICA I/O signal INT2 (Port E, pin 6 on ATMega128 or 51-pin Hirose connector pin
4) is used internally to the MICAz for the CC2420 Radio 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
software modules.