iRobot

iRobot - Transcript

Getting to know the iRobot Create
CSSE 120—Rose Hulman Institute of Technology
Show Off Some Animations

Who would like me to show off their work?

Otherwise I’ll pick some programs at random
Reviewing some concepts you read

Functions

Named sequences of statements

Can invoke them—make them run

Can take parameters—changeable parts
Parts of a Function Definition
>>> def hello():
print "Hello"
print "I'd like to complain about this parrot"
Defining a function
called “hello”
Indenting tells interpreter
that these lines are part of
the hello function
Blank line tells interpreter
that we’re done defining
the hello function
Defining vs. Invoking

Defining a function says what the function should do

Invoking a function makes that happen

Parentheses tell interpreter to invoke the function

Later we’ll define functions with parameters
>>> hello()
Hello
I'd like to complain about this parrot
Q1
A simple program that defines and
invokes a function called main()
# A simple program illustrating chaotic behavior.
# From Zelle, 1.6
def main():
print "This program shows a chaotic function"
x = input("Enter a number: ")
for i in range(10):
x = 3.9 * x * (1 - x)
print x
main()
comments
Define a function called “main”
A variable called x
An input statement
A loop
The loop’s body
Assignment statement
Invoke function main
Q2
Questions?

Your reading should be enough for you to do the
homework due Friday:

Modifications to chaos program

A program to calculate the distance between 2 points

Questions?

Up next: Robots!
Your iRobot Create

I’ll give each pair a locker number and combination.

Robots are in the lockers, currently sitting on the
dock (2 green lights on dock) and should be
returned to the dock at the end of the class to keep
them charged.

Please have one person get your robot from your
locker.

We’ll get names from the other partner.
Getting to know the iRobot Create
Look at your iRobot Create as we go!
Getting our hands on iRobot Create

iRobot Create hardware overview

Actuators

Sensors

Making a COM port connection over Bluetooth

iRobot Create’s Open Interface Protocol

Sending serial commands via RealTerm

Sending serial commands via Python

Using the create.py module!

Way Easier! Way Better!
iRobot Actuators – Robot Outputs

Left Wheel Motor

Right Wheel Motor
Max speed sets the
wheels to 500 mm/s
forwards or backwards
That’s just over
1 mph so don’t
get too excited
about 500 mm/s
Q3-4
iRobot Actuators – Robot Outputs

Left Wheel Motor

Right Wheel Motor

Speaker
iRobot Actuators – Robot Outputs

Left Wheel Motor

Right Wheel Motor

Speaker

Bi-color Power LED

Play LED

Advance LED
Q4
iRobot Actuators – Robot Outputs

Left Wheel Motor

Right Wheel Motor

Speaker

Bi-color Power LED

Play LED

Advance LED

Low-side Drivers on the BAM (LD0-LD2)

Digital Outputs on the BAM (DO0-DO2)
iRobot Sensors – Robot Inputs

Omnidirectional IR Sensor

Play and Advance Buttons

Left and Right Bumpers

Three Wheel Drop Sensors

Four Cliff Sensors

Wall Sensor

Encoders

Four Digital Inputs on the BAM (DI0-DI3)

Analog Input on the BAM (Ain)
Q5
Omnidirectional IR Receiver
IR receive shown here = 0b00110011
= 0x33
= 51
IR Visible
No IR Light
IR transmitters will flash out certain
patterns to send 8-bit numbers
Values 0 to 254 (255 is for no signal)
Play and Advance Buttons

Digital inputs that you
could really use for
any function

They just have symbols
on them. Nothing
special about that
symbol
Bump Sensors

Two digital signals

Left Bumper

Right Bumper
Wheel Drop Sensors

Three digital inputs

Front Wheel Drop

Left Wheel Drop

Right Wheel Drop
Cliff Sensors

Four analog inputs

Cliff Left Signal

Cliff Front Left Signal

Cliff Front Right Signal

Cliff Right Signal
Cliff Sensor Analog Readings
White
Surface
Gray
Surface
Black
Surface No Surface
High value
Max = 4095
Medium value Low value
Min = 0
Low value
Min = 0
1800 1000 0 0
Common real values:
Wall Sensor

One Analog Sensor

Value relates to the
distance between wall
and Create
0 = No wall seen
Wheel Encoders

More complex

Distance since last
request

Angle since last
request

Used internally to
control wheel speed
Inputs on the BAM

Four Digital Inputs on the BAM (DI0-DI3)

Analog Input on the BAM (Ain)
iRobot Create Top View
iRobot Create Bottom View
Getting our hands on iRobot Create

iRobot Create hardware overview

Actuators

Sensors

Sensor signals go to the iRobot microcontroller

But? The signals need to get to the computer?
How do we get this information to a PC?
UART Communication
Universal Asynchronous
Receiver / Transmitter
Example UART Basics
A quick detailed look at UART
Message at predetermined bit rate (baud rate) iRobot uses 57600 bits/second
How does UART work?

Usually (or maybe we should say previously) UART is/was
connected via an RS232 port, also known as a DB9 Serial Port,
or just called, more simply, a “Serial Port”
From Society of Robots website – “Let me say this bluntly - no cute girl would ever
date you if you have a robot with a long wire dragging behind it. Just that simple.”
TxRx Ground
Laptop Serial Port Serial Cable iRobot 25 pin Serial Port
Tx Rx
Ground
Wireless Bluetooth using the BAM!
Bluetooth Hardware
Inside Laptop Using
Bluetooth Driver
Bluetooth
“Virtual” Wires
BAM = Bluetooth Access Module
Communication Protocol

iRobot sets the rules for communication

iRobot store website http://store.irobot.com

Learn and practice the UART commands

Click on Educational… then Manuals
Owner’s Guide
Open Interface Specifications
 RealTerm

Let’s start with RealTerm

Sends UART messages over a COM port
Finding your Bluetooth device

If you installed the
Bluetooth driver from
HW1 you should have
a Bluetooth icon…

Double click on that
icon to bring up “My
Bluetooth Places”

Turn on Robot

Double click on “Find
Bluetooth Devices"
Finding YOUR iRobot Create BAM

Let your computer find all devices

Hover your mouse over an “Element Serial”

Find the number that matches the one printed on your BAM
Connect to Element Serial

Double click on the
“Element Serial on
Element Serial” to start
the Bluetooth pairing
process
Entering the Bluetooth security code

You should have a window pop up that says “You
need to enter a super top secret security code for
this Bluetooth Device

Click in that window

(if you are too slow and the window goes away,
click on the, now green, Bluetooth symbol directly)
This slide is Top Secret

The top secret code
for this Bluetooth
device is the number…
0000
Turns out every Bluetooth
device that doesn’t
care about security is
just four zeroes
Remember the COM port #

You should now be connected to the BAM!

It’s just like two virtual wires Rx and Tx for serial communication to the iRobot Create

You need to know the COM port #

It’s at the very bottom of the window (mine is COM port 6)

(if you are too slow you can always right-click and open the Bluetooth Properties)
Q6
(optional) Renaming your Element Serial

If you want you can rename your “Element Serial” to a name that is easier to find
in your Bluetooth Neighborhood. I called this one “StarWars#”

This only effects your computer, it doesn’t change anything on the BAM

Then next time you “Find Devices” it’s easier to spot in the list
What did we just do?
Bluetooth Hardware
Inside Laptop Using
Bluetooth Driver
Bluetooth
“Virtual” Wires
BAM = Bluetooth Access Module
We connected the Rx and Tx
wires… wirelessly!
Now we’re ready to send data!

Open RealTerm

Port tab

Set Port to your
COM port #

Set Baud Rate to
57600 bits/second

Click the Change
button to make it
actually happen
Send an LED command

Turn on the Play LED with an amber Power LED

Type 128 132 139 2 100 100

Click
“Send
numbers”

Watch!
Digital Sensor Readings

Let’s request bumper and cliff sensor data
Digital
Version
Here
Analog Sensor Readings

Request an analog value
Sending commands in Python

Open IDLE

Import the serial Python library

Make sure you are connected via Bluetooth

Open a Serial port Object called tty
Note: The serial module is zero based not 1 based so COM 6 is port 5 (sorry)
Sending commands in Python

Send commands one by one in Python instead
of RealTerm (kind of a brute force method)
Note: The serial module is zero based not 1 based so COM 6 is port 5 (sorry)
Make a function to setPlayLED

We could make an LED function
When you are finished, close the COM port connection.
Using create.py

So much better! So much easier!
HANDS-ON PYCREATE