3 Axis Accelerometer

www.ti.com

MSP-EXP430FR5739 User Experience Demo

2.2.4

Using Mode 3

– Accelerometer Demo

Mode 3 is entered by pressing switch S1 three times, followed by switch S2.

Upon entering this mode, the on-board accelerometer (see Figure 4) is calibrated. To aid this calibration

process, it is recommended to place the board on a level surface before entering the mode.

Figure 4. On-Board Accelerometer

After the calibration sequence is completed, LED4 and LED5 are turned on. When tilting the board in an

upward or downward direction, the LEDs follow the direction of the tilt. S2 toggles the display on and off,

similar to other modes.

Mode 3 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.

2.2.4.1

Displaying Results on the PC GUI

When in the accelerometer mode, the GUI mimics the LEDs that are lit up on the Experimenter Board and

are a reflection of the tilt of the board.

11

SLAU343B

– May 2011 – Revised February 2012

MSP-EXP430FR5739 FRAM Experimenter Board

Submit Documentation Feedback

Copyright

© 2011–2012, Texas Instruments Incorporated