Telos
Rev B (Low Power Wireless Sensor Module)
Moteiv Corporation
Telos (Rev B) : PRELIMINARY Datasheet (12/5/2004)
Page 25 of 28
Internal Temperature and Voltage Monitoring
The MSP430 microcontroller has internal temperature and voltage sensors that may be used
through the microcontroller’s ADC interface.
The voltage port (input 11) on the 12-bit ADC monitors the output from a voltage divider.
1
1
C
D
A
c
c
V
D
R
R
Voltage monitoring for Telos motes.
Converting the ADC units to a voltage reading can be done with the following formula:
R
R
2
V
4096
ADCCounts
DVcc
ref
×
×
=
The temperature input is internal ADC port 10. It consists of an uncalibrated diode. When using
the temperature sensor, the sample period must be greater than 30 µs. The temperature sensor
offset error can be large, and may need to be calibrated for most applications. The typical
response of the temperature sensor is shown in Figure 25.
Cels ius
Volts
0
50
100
1.000
0.800
0.900
1.100
1.200
1.300
–50
0.700
VTEMP=0.00355(TEMPC)+0.986
Figure 25 : Typical response of the internal temperature sensor. Results vary and the sensor
should be calibrated for most applications. Response curve from Texas Instruments.
