This document discusses programming a robot to drive forward indefinitely but stop and reverse if its bumper switch is pressed. [1] It introduces bumper switches, which output a 1 when pressed and a 0 when not pressed. [2] It presents a flowchart and pseudocode to describe the desired behavior. [3] The flowchart and pseudocode are then expanded on to more accurately represent the logic needed to program the behavior in ROBOTC.

1. VEX Robotics I Power Points
Topic 09
Programming Design Basics
Bumper Switch Sensing 1
www.pedagogics.ca

2. Topics Covered in this Presentation
Topic 09
• Introduction to the bumper switch
• flowcharting and writing pseudocode
•program sketch #1
• while loops and Boolean logic
• if else loops and sensor input

3. Bumper Switch
(digital sensor)
Usually positioned on front of robot.
Output is either a 1 (depressed) or a 0
0

4. Bumper Switch
(digital sensor)
Usually positioned on front of robot.
Output is either a 1 (depressed) or a 0
1

5. Bumper Switch
(digital sensor)
Usually positioned on front of robot.
Output is either a 1 (depressed) or a 0
0

6. Bumper Switch
(digital sensor)
Usually positioned on front of robot.
Output is either a 1 (depressed) or a 0
1

7. Program sketch #1
Write a simple program to make your robot drive forward
indefinitely , but will stop, turn 180o and continue driving if
the robot encounters an obstacle.
STEP 1 – FLOWCHART
• thinking about how ROBOTC works
STEP 2 – PSEUDOCODE
STEP 3 – ACTUAL CODE

8. Flowchart Symbols

9. START Flow chart describes behavior
sequence.
DRIVE
FORWARD
This flowchart gives us the basic
NO
idea of what behaviors we want to
Switch
pressed see in our robot.
?
YES The flowchart however is overly
simplified and needs a few extras to
Stop, reverse, 180
degree turn make it easily transferable to code.

10. Cannot use a wait statement because we want
START the robot to perform two functions alternately
(essentially simultaneously)
IF
Always Switch TRUE
WHILE DRIVE
not
LOOP ?
infinite pressed FORWARD
Move
on loop ?
FALSE
END Stop, reverse, 180
degree turn

11. DECISIONS must This type of question is called a Boolean
be thought of as statement.
questions that
can be answered The answer is called a “truth value” and
YES or NO the answer is only valid at the time the
TRUE or FALSE question is asked.
You used a Boolean statement in the
remote control coding for Tumbler

12. Valid “comparison operators” in ROBOTC

13. START
Pseudo code - basic commands, comments about
functions and behaviors
This code will never compile
Forms the backbone of your program and translates
from the flowchart to ROBOTC

15. IF , ELSE boolean statement used to check
bumper switch. If switch is not pressed, robot
START drives forward
IF
Always Switch TRUE
WHILE DRIVE
not
LOOP ?
infinite pressed FORWARD
loop ?

17. IF , ELSE boolean statement used to check
START bumper switch. If switch is not pressed, robot
drives forward
IF
Always Switch TRUE
WHILE DRIVE
not
LOOP ?
infinite pressed FORWARD
loop ?

19. If switch is pressed – ELSE – the stop and turn
START behavior occurs, then robot returns to moving
forward (unless what is happening?)
IF
Always Switch TRUE
WHILE DRIVE
not
LOOP ?
infinite pressed FORWARD
loop ?
FALSE
Stop, reverse, 180
degree turn

21. START
IF
Always Switch TRUE
WHILE DRIVE
not
LOOP ?
infinite pressed FORWARD
Move
on loop ?
FALSE
END Stop, reverse, 180
degree turn