VEX Robotics I Power Points

Topic 09

Programming Design Basics

Bumper Switch Sensing 1www.pedagogics.ca

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

Bumper Switch

(digital sensor)

Usually positioned on front of robot.

Output is either a 1 (depressed) or a 0

0

Bumper Switch

(digital sensor)

Usually positioned on front of robot.

Output is either a 1 (depressed) or a 0

1

Bumper Switch

(digital sensor)

Usually positioned on front of robot.

Output is either a 1 (depressed) or a 0

0

Bumper Switch

(digital sensor)

Usually positioned on front of robot.

Output is either a 1 (depressed) or a 0

1

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

Flowchart Symbols

Flow chart describes behavior

sequence.

This flowchart gives us the basic

idea of what behaviors we want to

see in our robot.

The flowchart however is overly

simplified and needs a few extras

to make it easily transferable to

code.

DRIVE FORWARD

START

Switch pressed

?

Stop, reverse, 180 degree turn

NO

YES

DRIVE FORWARD

START

IF Switch

not pressed

?

Stop, reverse, 180 degree turn

TRUE

FALSE

WHILE LOOP ?

END

Move on

Always

infiniteloop

Cannot use a wait statement because we want the robot to perform two functions alternately (essentially simultaneously)

DECISIONS must be thought of as questions that

can be answered YES or NO

TRUE or FALSE

This type of question is called a Boolean statement.

The answer is called a “truth value” and the answer is only valid at the time the question is asked.

You used a Boolean statement in the remote control coding for Tumbler

Valid “comparison operators” in ROBOTC

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

DRIVE FORWARD

START

IF Switch

not pressed

?

TRUEWHILE LOOP ?

Always

infiniteloop

IF , ELSE boolean statement used to check bumper switch. If switch is not pressed, robot drives forward

DRIVE FORWARD

START

IF Switch

not pressed

?

TRUEWHILE LOOP ?

Always

infiniteloop

IF , ELSE boolean statement used to check bumper switch. If switch is not pressed, robot drives forward

DRIVE FORWARD

START

IF Switch

not pressed

?

Stop, reverse, 180 degree turn

TRUE

FALSE

WHILE LOOP ?

Always

infiniteloop

If switch is pressed – ELSE – the stop and turn behavior occurs, then robot returns to moving forward (unless what is happening?)

DRIVE FORWARD

START

IF Switch

not pressed

?

Stop, reverse, 180 degree turn

TRUE

FALSE

WHILE LOOP ?

END

Move on

Always

infiniteloop