Datasheet

Tactile Navigation with Whiskers • Chapter 5
Robotics with the BOE Shield-Bot • 169
4. What statements did this chapter use to call different navigation functions based
on whisker states?
5. What is the purpose of having nested
if statements?
Exercises
1. Write a routine that uses a single variable named whiskers to track whisker
contacts. It should store a 3 when no whiskers are contacted, a 2 if the right
whisker is contacted, a 1 if the left whisker is contacted, or 0 if both whiskers are
contacted. Hint: multiply the result by two.
2. Modify the
loop function in RoamingWithWhiskers so that it makes the BOE
Shield-Bot stop and not restart when both whiskers contact at the same time.
3. Add a function named
pause to RoamingWithWhiskers. It should make the BOE
Shield-Bot stay still for a certain amount of time.
4. Modify the
loop function so that the BOE Shield-Bot stays still for 0.5 seconds
before backing up and turning.
Projects
1. Modify RoamingWithWhiskers so that the BOE Shield-Bot stops and makes a 4
kHz beep that lasts 100 ms before executing its usual evasive maneuver. Make it
beep twice if both whisker contacts are detected during the same sample. HINT:
Use the
pause function you developed in the Exercises section to make it pause
immediately after the tone starts playing. Also, a 0.2 second pause after the tone
call separates the 0.1 second tone from servo motion, or allows you to hear a
second tone.
2. Modify RoamingWithWhiskers so that the BOE Shield-Bot roams in a 1 yard (or 1
meter) diameter circle. When you touch one whisker, it will cause the BOE
Shield-Bot to travel in a tighter circle (smaller diameter). When you touch the
other whisker, it will cause the BOE Shield-Bot to navigate in a wider diameter
circle.
Question Solutions
1. A normally open, momentary, single-pole, single-throw tactile switch.
2. Zero (0) volts, resulting in binary zero (0) returned by
digitalRead.
digitalRead(8)== 0 when whisker is pressed.
digitalRead(8)== 1 when whisker is not pressed.
3.
digitalRead(7)== 1 means the right whisker is not pressed.
digitalRead(7)== 0 means the right whisker is pressed.
digitalRead(5)== 1 means the left whisker is not pressed.
digitalRead(5)== 0 means the left whisker is pressed.
4. This chapter used
if, if…else, and if…else if…else statements to evaluate
whisker conditions and call navigation functions.