CSC 161	Grinnell College	Spring, 2015

Imperative Problem Solving and Data Structures

Sensors for the Scribbler 2 Robot

A Scribbler 2 robot has numerous sensors for detecting the world. The MyroC library provides a full range of functions, with multiple ways to access the data. Each function allows values of the sensor to be queried several times with an average value returned.

The following figures indicate which functions reference which sensors.

Scribbler forward

Sensor Set	Vector Function	Text Functions	Values Returned	Typical Variability	Comments
Light Sensors (really darkness sensors)	int vals[3] int n; /sampleSize/ rGetLightAll(vals, n);	int n; /sampleSize/ rGetLightTxt("left", n); rGetLightTxt("middle", n); rGetLightTxt("right", n);	bright light returns values near 0; dark areas return large integers (about 65535)	under 5%-10%	bright, direct light needed for small-value results

IR Scribbler Sensors	int vals[2] int n; /sampleSize/ rGetIRAll(vals, n);	int n; /sampleSize/ rGetIRTxt("left", n); rGetIRTxt("right", n);	output 0 indicates no obstacle; output 1 indicates obstacle	substantial variation likely; sample several times for average	light must reflect from emitter to receiver, so obstacle must be a 4-6 inches away

Fluke forward

Sensor Set	Vector Function	Text Functions	Values Returned	Typical Variability	Comments
Obstacle Sensors	int vals[3] int n; /sampleSize/ rGetObstacleAll(vals, n);	int n; /* sampleSize */ rGetObstacleTxt("left", n); rGetObstacleTxt("middle", n); rGetObstacleTxt("right", n);	values near 0 indicate no obstacle (no light reflected from emitters) large integers (near 6,000) indicates obstacle	substantial variation possible; sensor values degrade as battery degrades	value returned depends upon battery strength and output; level of emitters (set by rSetIRPower(level), where level in range 0, 255) values under 1000 are likely to imply no obstacle values over 5000 are likely to imply an obstacle values between 1000 and 5000 may not give definitive results

Virtual Light Sensors	int vals[2]; int n; /* sampleSize */ rGetBrightAll(vals, n);	int n; /* sampleSize */ rGetBrightTxt("left", n); rGetBrightTxt("right", n);	values near 0 represent bright light; values may extend to about 65535 for very dark region	variation of 5000-10000 common	averaging encouraged for modest consistency

This document is available on the World Wide Web as

http://www.walker.cs.grinnell.edu/courses/161.sp14/scribbler2-sensors.shtml

created created 19 March 2012 by Henry M. Walker revised 25 March 2012 by Henry M. Walker revised (developmental library added) 23 January 2014 by Henry M. Walker> revised (developmental library added) 23 January 2014 by Henry M. Walker> revised (old functions removed) 3 November 2014 by Henry M. Walker
For more information, please contact Henry M. Walker at walker@cs.grinnell.edu.

Copyright © 2011-2015 by Henry M. Walker.
Selected materials copyright by Marge Coahran, Samuel A. Rebelsky, John David Stone, and Henry Walker and used by permission.
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