weston schreiber & joshua gabrielse robotics summer training programming #3: intro to...

Weston Schreiber & Joshua Gabrielse

Robotics Summer Training

Programming #3: Intro to Computational Thinking


Objectives:• Understand the 3 stages to programming• Create an algorithm that accomplishes a

programming task• Understand the purpose of variables, if

statements, loops, and functions in programs


1st Rule of Programming

Computers are stupid!!!!

They do EXACTLY what they are told,

nothing less, nothing more, and they never get the

idea.


Stage 1: Planning(Algorithm, Flowchart, Pseudocode)

Stage 2: Coding(Variables, Functions, if statements, Loops)

Stage 3: Error Analysis(Syntax Errors, Logic Errors, Readdress Plan)



Flowcharts & Algorithm Planning• Two Types of Parts to a Programming Flowchart:

Actions Decisions

“Yes”

“No”

Robotics Examples“Turn on wheel motors” “Is the front bumper

pushed?”

“Lift Gripper Arm” “Has the robot turned 3 times?”

“Stop all motors” “Has the encoder registered over 1000 counts?”


Flowcharts Recap:

If the answer to Question 1 is “yes,” and the answer to Question 2 is “no,” what order do the steps happen?

Click the number corresponding to the correct answer on your clicker.

A) Step 1, Step 2

B) Step 2, Step 3B

C) Step 1, Step 2, Step 3A

D) Step 1, Step 2, Step 3B


Basics of Computer Programming

Variables- place to store changeable information

Functions- block of reusable code

Conditional ( if ) Statements - code that only runs if a condition is TRUE

Loops (while, for )- section of code that repeats





•What are some variables in your everyday life?

•What are some variables PowerPoint is storing to run this presentation?


VariablesA place to store changeable information.

BEGIN

END

int x

Example:

Create a variable (a place to store integers) called x.

Assign x a value of 1.

Assign x the value of the expression 1 + 2.

Assign x equal to the previous value of x plus 1.

x = 1

x = 1 + 2

x = x + 1


What is the value of x after line 1?

BEGIN

END

int x

Example:





x = 1

x = 1 + 2

x = x + 1

line 0

line 1

line 2

line 3


A) 1 B) 2 C) 3 D) 4 E) 5 F) 0 G) a random number



BEGIN

END

int x

Example:





x = 1

x = 1 + 2

x = x + 1

line 0

line 1

line 2

line 3




Declaring Variables

Computers & robots need to know three things in order to create variables:1.Type: how much memory to reserve, and how it is used

• Integers take less memory than floating point decimals.• Example:

• 1 (int) it takes less memory just to store the number• 1.0 (float) it takes extra memory to store the location of

the decimal point2.Name: how to refer to/locate the reserved memory

• Pick names that are logical and easy to remember3.Value: what to store in that memory

• If you don’t give an initial value, whatever random value is left in that memory location will remain there

Double click on the variables block in the flow chart of any function to declare (create) variables.


Declaring Variables(simplified)

Pick:1. Type: what kind of information is being stored

2. Name: a descriptive identifier (you pick the name)

3. Value: the information initially stored in the variable

Double click on the variables block


Variable Types

When in doubt, pick int!

Need to use decimals?

Use double!


What are the key parts to a function?Click the number corresponding to the correct answer on your clicker.

A) Name, Type, Value

B) Name, Parameters, Description

C) Name, Parameters, Action

D) Name, Description, Value

Functions Recap:




•What are some “functions” in your daily life?

•What are some functions PowerPoint might use to run this presentation?


EasyC Built-In Functions:All the tools we’ll need to control the flow of the program (or, which code to run and when to run it)

Important Function: Wait( ms )


Writing Your 1st Program

1. Write a Plan for your Controller Setup

2. Start a New Program

3. Operator Control

4. Build & Download to Robot

5. Autonomous Program


Objectives:• Create a simple autonomous

program

• Have your robot drive on its own!

• Create an autonomous program for your robot to score a goal.


Autonomous Goal #1:

• Drive forward and stop.


Which set of function calls would correctly accomplish our goal?Click the number corresponding to the correct answer on your clicker.

A. B. C. DriveStraight()

Stop()

Wait()

DriveStraight()

Wait()

Stop()

DriveStraight()

Wait()

Stop()



• Recall the functions we discussed the other day

•DriveStraight(), Stop()

• Write the code for those functions.

• Create your autonomous program!


Competition SwitchesEnable/Disable & Autonomous/Operator Control

Hardware: plug the ethernet cable into the competition port on the joystick

Software: the computer has to be connected directly to the robot controller or through VEXnet from the joystick (via the programming port)


• Basics of Program Complete

• Rest: Advanced Concepts


Naming Conventions

1. Pick descriptive names.

2. Follow capitalization standards• Variable names start with lower case letters.• Function names start with capital letters.• Constants are all capitals.

3. Use camel case for multi-word names.• Example 1: camelCase• Example 2: CamelCase


What is DriveForward according to our naming

convention?

A) a variable

B) a function

C) a constant

D) it doesn’t fit our naming convention


What is PUSHED according to our naming

convention?

A) a variable

B) a function

C) a constant


I’m supposed to be pushing the button

with my nose.


What is frontBumper according to our naming

convention?

A) a variable

B) a function

C) a constant



If Conditions – Structure & Function

Condition: any statement that can be evaluated as true or false.

CONDITION

ACTION

• IF the CONDITION is TRUE the ACTION happens and the program continues after the IF.

• IF the CONDITION is not true the ACTION never happens and the program continues after the IF.


If Conditions – Structure & Function

Condition: Compares two variables/values using a comparison operator

Symbol Definition== equal!= not equal> greater than

>= greater than or equal to

< less than<= less than or equal to

( A [symbol] B )

Double equal signs (==) check to see if a statement is true.

Ex: x == 4

Single equal signs (=) assign a value to a

variable. Ex: x = 4

Assign is just programmer-talk for “set equal to.”


If Conditions – Check Your Understanding

Example If Condition:

Based on variable values, what functions will run?


A) DontVote()B) GoShopping()C) DontVote(), then GoShopping()D) No functions will runE) age < 18






A) GetMoreSupplies()B) TeachArtProject()C) GetMoreSupplies(), TeachArtProject()D) TeachArtProject(), GetMoreSupplies()E) No functions will run

numStudents = 22;






A) TurnFor(), DriveStraightFor()B) DriveStraightFor(), TurnFor()C) frontBumper == PUSHED, DriveStraightFor()D) DriveStraightFor()E) TurnFor()F) No Functions will run

frontBumper = 0;


If Else Conditions – Structure & Function

• IF the CONDITION is TRUE, ACTION #1 happens and the program continues after the IF.

• IF the CONDITION is FALSE, ACTION #2 happens and the program continues after the IF.

CONDITION

ACTION #1

ACTION #2


If Else Conditions – Check Your Understanding



A) BuyVideoGame()B) BuyBook()C) BuyLunch()D) BuyVideoGame(), BuyBook()E) BuyVideoGame(), BuyLunch()F) BuyBook(), BuyLunch()G) All 3 functions will runH) No functions will run

money = 100;


If Else Conditions – Check Your Understanding



A) DriveStraight()B) Stop()C) FlashLEDS()D) DriveStraight(), Stop()E) DriveStraight(), FlashLEDS()F) Stop(), FlashLEDS()G) All 3 functions will runH) No functions will run

backBumper = 1;


While Loops – Structure & Function

Condition: any statement that can be evaluated as true or false.

WHILE the CONDITION is TRUE, keep doing the ACTION(S) repeatedly.

Once the CONDITION is FALSE, the ACTION stops happening and the program continues after the WHILE.

CONDITION

ACTION


While Loops – Structure & Function

3 Outcomes for a While LoopCONDITION

ACTION

In the C Programming Language:1 = TRUE0 = FALSE

– So –While (1) is always true

and the program is stuck in an endless loop

Loop runs forever Loop runs a number of times and stops

Loop is skipped and never runs

Loop runs forever Loop runs a number of times and stops

Loop is skipped and never runs

• The condition stays TRUE forever

• The condition starts TRUE, but eventually evaluates as FALSE

• The condition is FALSE initially


While Loops – Check Your Understanding

Example:

Based on variable values, how many times will the loop repeat before running GoToATM()?


A) The loop will never run.B) 1 timeC) 4 times D) 5 timesE) The loop will never stop



Example:

Based on variable values, what actions will the robot take?Click the number corresponding to the correct answer on your clicker.

A) The robot will drive straight ahead.B) The robot won’t move.C) The robot will turn for a bit, then drive straight ahead.D) The robot will turn in a circle continuously, never stopping.



Example:

Based on variable values, what actions will the robot take?Click the number corresponding to the correct answer on your clicker.

A) Drive straight, then Turn continuously.B) Drive straight forever.C) Drive straight, Turn, then Stop.D) Drive straight, then Stop.


Autonomous Flowchart (Easier)

• Make a flow chart for a robot with a bumper switch in the front.

• The robot drives forward, stopping when it hits something.

Function HintsDriveForward()CheckFrontBumper()


Autonomous Flowchart (Harder)

• Make a flow chart for a robot with a bumper switch in the front and the back.

• Every time the robot runs into something it changes direction.

Function HintsDriveForward()DriveBackward()CheckFrontBumper()CheckBackBumper()


One P

ossible Algorithm


One P

ossible Algorithm

Equivalent C-Code Generated by EasyC

Go to Window Block & C Programming in EasyC to see both the flowchart and the C code.


Aids for Teaching Programming

• Stratch – Intro Programming Tool designed at MIT

– http://scratch.mit.edu/

• Code Academy – Online Instruction/Challenges

– http://www.codecademy.com

• Lucid Charts – Nice web-based Flowchart Creator

– http://www.lucidchart.com/ • Flow Chart Practice

– http://www.cimt.plymouth.ac.uk/projects/mepres/book8/bk8i1/bk8_1i2.htm

weston schreiber & joshua gabrielse robotics summer training programming #3: intro to...

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