1.0 INTRODUCTION
The DLP-TILT USB-to-accelerometer module has four primary applications: (1) vibration analysis, (2) tilt
sensing, (3) AC signal analysis, and (4) two-button mouse pointing device alternative.
1.1 VIBRATION ANALYSIS
This module is designed to provide vibration analysis using an on-board, 2-axis, 1.5g accelerometer that is
designed for analysis of frequencies up to 350 Hz. Two of the analog channels in the microcontroller are
dedicated to the on-board accelerometer.
1.2 TILT SENSING
When used as a tilt sensor, the accelerometer can measure tilt up to approximately ±60 degrees from center in
both the X- and Y-axes. The position is reported as an 8-bit or 10-bit integer with the center position reporting
the half-scale value of 128 (8-bit) from the A/D converter in the microcontroller. The A/D converter can also be
run in 10-bit resolution mode with a resulting mid-scale value of 512. The Z-axis measurement data is also
available as a simple voltage measurement.
1.3 AC SIGNAL ANALYSIS
Voltage data from the seven analog channels can be sampled at rates ranging from 100 samples per second to
6000 samples per second, thereby enabling AC analysis of audio frequencies up to 3KHz. One module input
channel is dedicated to an analog input buffer that allows for voltages in the range of ±5 volts to be acquired.
The remaining channels allow voltages in the range of 0-5 volts to be acquired.
The microcontroller and preprogrammed firmware used in this design utilize single-byte commands to control all
aspects of operation. Once the channel and sample rates have been selected, continuous streaming of A/D
data can be enabled and disabled by sending a single-byte command. Data received by the host PC can be
analyzed for frequency content using an FFT-based Windows application available as a free download from the
DLP Design website upon purchase of the module.
1.4 POINTING DEVICE
The DLP-TILT’s preprogrammed firmware includes the feature set of a standard two-button mouse with the
motion of the cursor controlled by the tilt of the DLP-TILT’s printed circuit board and accelerometer.
When the board is level, the cursor remains motionless. As the board is tilted from center, the cursor begins to
move in the direction of the tilt. The further the board is tilted, the faster the cursor moves across the screen.
Two of the digital I/O lines serve as inputs for the buttons. Shorting these lines to ground will cause the
firmware to issue the “Button Down” signal to the host PC, thereby mimicking the operation of standard mouse
buttons.
Shorting a pin to ground in the interface header before powering up the DLP-TILT activates the two-button
mouse functionality. Refer to Section 2.0 for the I/O lines associated with the Pointing Device mode of
operation.
Rev. 1.1 (May 2009)
2
? DLP Design, Inc.