NTC Thermistor
MSP-EXP430FR5739 User Experience Demo
2.2.5
Using Mode 4
–
Temperature Sensor Demo
Mode 4 is entered by pressing switch S1 four times, followed by switch S2.
Upon entering this mode, the on-board thermistor (see
) is calibrated.
Figure 5. On-Board NTC Thermistor
After the calibration sequence is completed, LED4 and LED5 are turned on. When the NTC resistor is
heated (for example, by placing a finger on it), LED3 through LED1 are turned on sequentially. When the
NTC is cooled (for example, by using a freeze spay or a keyboard dust remover that uses compressed air)
LED5 through LED8 are turned on sequentially.
Similar to Mode 3, Mode 4 also writes the sampled data from the ADC to the FRAM in real time with no
wait states or extra cycles spent on setting up the FRAM. This can be observed in the ADC interrupt
service routine. The sampling takes place at more than 15k samples per second. At this speed, flash
devices require that the data be buffered in RAM before writing to flash. In FRAM devices, the only
bottleneck is the speed at which the ADC can sample, not the writes to nonvolatile memory.
2.2.5.1
Displaying Results on the PC GUI
When in the temperature sense mode, the GUI mimics the LEDs that are lit up on the Experimenter Board
and are a reflection of the thermistor's ambient temperature measurement.
12
MSP-EXP430FR5739 FRAM Experimenter Board
SLAU343B
–
May 2011
–
Revised February 2012
Copyright
©
2011
–
2012, Texas Instruments Incorporated
