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The camera system used in the LRF Module has automatic white balance, automatic exposure, and
automatic gain control enabled by default, and will automatically adjust its image to account for sudden
changes in lighting conditions. However, the LRF works best in a controlled environment, such as indoors
with minimal changes in brightness across the frame. The LRF is also less reliable when the laser is
shining onto a bright object (for example, a white piece of paper), since the background subtraction
performed during image processing could potentially "subtract" the bright laser from the already bright
frame.
Status Indicator
A visual indication of the LRF Module's operating state is given with the on-board LED (Light-Emitting
Diode). The LED is located on the back side of the LRF near the center of the board. The LED denotes
four states of the LRF:
1. Green: Idle state. Waiting for a command to be sent by the host.
2. Red: Active state. For example, performing a range calculation or capturing an image with the
camera.
3. Orange (Solid): Baud rate detection state. The LRF is waiting for a "U" character to be sent by
the host in order to automatically set the communications baud rate. Occurs on LRF power-up
only.
4. Orange (Blinking): Error state. The LRF has malfunctioned. A message identifying the failed
operation will be transmitted on the SOUT (Serial Out) pin. See Error Modes, page 10, for details.
If the LED is OFF, the LRF may not be receiving power.
Command Set
All commands are single-byte, ASCII printable values and are not case-sensitive (upper case and lower
case will both work). No carriage return (CR) or linefeed (LF) is required after the command byte is sent.
Depending on the command, data may be returned by the LRF.
The command descriptions in this section are for LRF firmware version 2.0. For command descriptions of
earlier firmware versions, refer to product manual version 1.1. Examples are shown for direct connection
to a microcontroller (BASIC Stamp 2) and/or to a host PC via a terminal program.
R
Single range measurement (returns a 4-digit ASCII value in millimeters)
B
Single range measurement (returns a 2-byte binary value in millimeters)
L
Repeated range measurement (any subsequent byte will stop the loop)
E
Adjust camera for current lighting conditions
S
Reset camera to initial settings
T
Toggle laser on/off
V
Display version information
H
Display available commands
Copyright © Parallax Inc.
Basic Commands
Parallax Laser Range Finder (#28044)
v2.0 10/31/2015 Page 3 of 23
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