Upload
mc-rene-solis-r
View
3.278
Download
1
Embed Size (px)
DESCRIPTION
All the *.PDE archives code are in this URL shared:http://www.4shared.com/file/196000558/ca6624de/bionicarduino-sketches.html
Citation preview
Bionic Arduino
Introduction to Microcontrollers with Arduino
Class 1
11 Nov 2007 - machineproject - Tod E. Kurt
Class Info• Thumbdrive is being passed around, with:
• PDF version of these notes
• Arduino software for Mac OS X & Windows
• Source code (“sketches”) used in class
• Copy files off, then pass thumbdrive around
• Sunday classes: 3 hours
• two ~1.5 hour chunks, w/ 15 min. break in middle
• Tuesday classes: ~2.5 hours
• with some review at the beginning
What’s for Today
• Introduction to Arduino
• Setting up your Arduino Environment
• Your first Arduino sketch
• Basic digital & analog output control
• Basic digital sensor inputs
• Making LEDs glow and blink on command
• How to read buttons & switches
Bionic?Can electronic senses mimic human ones?
Do electronic “muscles” work as well as biological ones? Or better?
What can electronic senses detect that humans can’t?
How would you augment yourself with these new abilities?
This class is about exploring the various input & output components used in robots, cell phones, video games, and automobiles, using the friendly Arduino board.
Your devices are watching and responding to you, know their limitations so you can defeat them when the machine uprising comes.
At worst, you’ll be able to fashion a convincing disguise from pasting Arduinos on your body.
Class Kit I Contents
Class Kit 2 comes next weekA little shoebox-sized plastic storage bin makes a good holder for your electronics stuff.
Not shown, RGB LED. oops. It showed up late to the photoshoot.
Class Kit 1 Manifest• Arduino Diecimila USB board
• Solderless breadboard
• USB cable
• piezo buzzer
• potentiometer with knob
• 5 orange LEDs (large, clear)
• 1 RGB LED (diffuse, com. anode)
• two push switches
• 9V battery and connector
• resistors:• 6 x 220 ohm (red-red-brown)
• 2 x10k (brown-black-orange)
• 1 x1M (brown-black-green)
• photocell
• phototransistor (small,clear)
• 4 colors of hookup wire
• rubber bands
There will be a second update kit next week: “motion & motors”
Setup and “light & sound”
A Word on Safety
• Electronics can hurt you
• Lead in some of the parts
• Wash up afterwards
• You can hurt electronics
• Static-sensitive: don’t shuffle your feet & touch
• Wires only bend so much
What is Arduino? The word “Arduino” can mean 3 things
A physical pieceof hardware
A programmingenvironment
A community& philosophy
Arduino Philosophy & Community
• Open Source Physical Computing Platform
• “open source hardware”
• open source: free to inspect & modify
• physical computing. er, what? ubiquitous computing, pervasive computing,
ambient intelligence, calm computing, everyware, spimes, blogjects, smart objects...
• Community-built
• Examples wiki (the “playground”) editable by anyone
• Forums with lots of helpful people
Arduino Hardware
• Similar to Basic Stamp (if you know of it)
• but cheaper, faster, & open
• Uses AVR ATmega168 microcontroller chip
• chip was designed to be used with C language
The designer of the AVR purposefully arranged its registers and instruction set so that C programs would compile efficiently on it. This is a big deal, compared to previous microcontrollers where C programs were almost always less efficient than a hand-coded assembly language variant.
Arduino Hardware Variety
USB
“Stamp”-sized
Bluetooth
LilyPad(for clothing)
DIY
many different variations to suite your needs
Boarduino Kit
Openness has its advantages, many different varieties.Anyone can build an Arduino work-alike in any form-factor they want.Product images from Sparkfun.com and Adafruit.com
Arduino Capabilities• 16 kBytes of Flash program memory
• 1 kByte of RAM
• 16 MHz (Apple II: 1 MHz)
• Inputs and Outputs
• 13 digital input/output pins
• 5 analog input pins
• 6 analog output pins*
• Completely stand-alone: doesn’t need a computer once programmed
* only sorta analog, uses PWM , which we’ll talk about later.
Don’t worry if the above doesn’t make sense, you don’t really need to know it.
Arduino Diecimila Board
2.7”
2”
resetbutton
powerLED
digital input/output “pins”
analog input “pins”
test LEDon “pin” 13
TX/RXLEDs ATmega168
USB interface
Arduino Terminology
“sketch” – a program you write to run on an Arduino board
“pin” – an input or output connected to something.
e.g. output to an LED, input from a knob.
“digital” – value is either HIGH or LOW.
(aka on/off, one/zero) e.g. switch state
“analog” – value ranges, usually from 0-255.
e.g. LED brightness, motor speed, etc.
Arduino Software
• Like a text editor
• View/write/edit sketches
• But then you program them into hardware
If you’ve used Processing to write little Java programs, you’ll notice the interface looks familiar.Arduino takes the editor GUI from Processing and some of its philosophy, but Arduino code and Processing code are totally unrelated.
Installing Arduino
1. Get the Arduino software & unzip it
2. Plug in Arduino board
3. Install the driver
4. Reboot
5. Run the Arduino program
6. Tell Arduino (program) about Arduino (board)
The Steps
Getting and Unpacking• On the thumbdrives
• “arduino-0010-win.zip” for Windows
• “arduino-0010-mac.zip” for Mac OS X
• Unzip the zip file. Double-click on Mac
Use “Extract All...”
On Windows, right-click
• Find the “drivers” directory inside
Plug in Arduino boardquick blink
from test LED
Power LED should stay on
Mac Driver Install
• v2_1_6 for PPC Macs
• v2_2_6 for Intel Macs
Double-click on .dmg Installer
Windows Driver Install
Selecting Location & Type
usually highest-numbered port
pick “Diecimila”
Selecting Location & Type
pick “Diecimila”
starts with tty.usbserial-
Arduino Software
compile(verify)
statusarea
upload to board
Using Arduino
• Write your sketch
• Press Compile button (to check for errors)
• Press Upload button to program Arduino board with your sketch
Try it out with the “Blink” sketch!
blink blink
compile
upload
sketch runs
TX/RX flash
Load “File/Sketchbook/Examples/Digital/Blink”
Change the “delay()” values to change blink rate
Status Messages
Uploading worked
Wrong serial port selected
Wrong board selected
Size depends oncomplexity of your sketch
nerdy cryptic error messages
Troubleshooting
• Most common problem is incorrect serial port setting
• If you ever have any “weird” errors from the Arduino environment, just try again.
• The red text at the bottom is debugging output in case there may be a problem
• Status area shows summary of what’s wrong
I made an LED blink, so what?
• Most actuators are switched on and off with a digital output
• The digitalWrite() command is the software portion of being able to control just about anything
• LEDs are easy, motors come in a bit
• Arduino has up to 13 digital outputs, and you easily can add more with helper chips
Development Cycle
• Make as many changes as you want
• Not like most web programming: edit ➝ run
• Edit ➝ compile ➝ upload ➝ run
compile upload runedit done!
Lots of Built-in Examples
And more here:http://www.arduino.cc/en/Tutorial/HomePage
And all over the Net. Search for “Arduino tutorial” or “Arduino notes” or whatever you’re interested in and “Arduino” and likely you’ll find some neat pages.
Take a Break
Grab a coffee upstairs at Downbeat Cafe.
Arduino “Language”• Language is standard C (but made easy)
• Lots of useful functions
• pinMode() – set a pin as input or output
• digitalWrite() – set a digital pin high/low
• digitalRead() – read a digital pin’s state
• analogRead() – read an analog pin
• analogWrite() – write an “analog” value
• delay() – wait an amount of time
• millis() – get the current time
• And many others. And libraries add more.
Also: serial library, LCD library, servo examples
Sketch structure
• Declare variables at top
• Initialize
• setup() – run once at beginning, set pins
• Running
• loop() – run repeatedly, after setup()
Pins can be changed in loop() too, but conceptually easier in setup()
Making Circuits
heart pumps, blood flows voltage pushes, current flows
It’s all about the flow of current. Kinda like the flow of liquid.Some electronics devices hold back current, like a tiny hose. These are “resistors”.
Example: LED flashlight
wiring diagram schematic wiring it up
Electricity flows in a loop. Can stop flow by breaking the loop
current flow
9V
+
–
LED
resistor500 ohm(green,brown,brown)
(flat part)
500
All LED circuits are essentially this: power source, current limiter, LEDFlat part of LED goes to negative, like bar in schematicThe higher the resistance, the dimmer the LED; the lower, the brighterYou don’t have to wire this up, but the following circuits are just the same
The Circuit for LED Blink
LED
resistor220 ohm(red,red,brown)
flat part
wiring diagram
Arduinoboard
gnd
pin 13
gnd
resistor
LED
schematic
“hello world” of microcontrollers
Arduino Diecimila board has this circuit built-inTo turn on LED use digitalWrite(13,HIGH)
This is a “computer-controlled LED flashlight”.In schematics signals often flow from top-left to bottom-right.Common nodes like “gnd” are given their own symbol.You could wire this circuit up on any digital pin, doesn’t matter which.Same circuit as last page, but “battery” is pin 13 of Arduino, and you can turn it on and off.
Schematics are pretty easy to learn, not many people use wiring diagrams.
LEDs & Resistors
LED
resistor
On LEDs, polarity matters.Shorter lead is “negative” side, goes to ground
Polarity doesn’t matter on resistors
Flat edge here for neg. side
Varying LED Brightness
wiring diagramschematic wired up
The PWM pins work with the “analogWrite(value)” command
To turn LED to half-bright, use analogWrite(9,128)
Same circuit as Blink circuit but pin 9 instead of pin 13
resistor220 ohm(red,red,brown)
fla
t p
artArduino
board
gnd
pin 9
gnd
resistor
LED
where “value” ranges between 0 and 255.
More about PWM later, but it only works on those pins labeled “PWM”.
Very quickly, it works by making and breaking the flow several hundred times a second. So really it’s flashing, just like blink, but doing it very fast. Our eyes make it look like brighter or dimmer.We’ll have to build this circuit.
Let’s Wire It Up
Arduinoboard
gnd
pin 9
gnd
resistor
LED
Going from schematic to physical circuit.
Solderless Breadboards
notconnected
All connected, a “bus”
numbers & letter labels
just for reference groups of 5
connected
Insert wires into holes to make a connection.*Much* easier, quicker than solderingBut, they wear out, are kind of expensive ($5 for this one, at that was a bargain)
Useful ToolsWire cutters
Needle-nosepliers
Wire stripper
Even with solderless breadboards you’ll need to cut and strip wire. Each of these costs around $5 each. If you have to get just one, get the wire stripper.
Making Jumper Wireswire stripperpliers & cutter
~1/4”
About 1/4” for the stripped parts. And as long as you need for your circuit.
Using Solderless Breadboards
Using needle nose pliers can helppush wires & components into holes
Grab wire or lead toward end and push into hole
All Wired Up
plugged into “ground” bus
Alternate Way
1. rubber band
Or, adding a breadboard to Arduino for 1¢
2. power & gnd wires3. plug into “bus” terminals
4. jumper overto other side
now circuit has power & groundThis makes it a bit easier to deal with wiring up circuits for two reasons.First, it secures the breadboard and Arduino together, so wires are less likely to come loose.Secondly, it gives you lots of power and ground holes, which you usually need a lot of.
Use this setup for the rest of your circuits.
Rubber band trick around Arduino & solderless breadboard shameless stolen from Kimiko Ryokai’s Tangible User Interface class (INFO290-13): http://courses.ischool.berkeley.edu/i290-13/f07/
LED “Fading” SketchLoad “File/Sketchbook/Examples/Analog/Fading”
Press “Upload”. After a second, LED will “throb” on and off
Reduce “delay()” values to make it go faster
note
Try other PWM pins (remember: you have to rewire)
Things to Try With “Fading”
• Make it go really fast or really slow
• Fading from half- to full-bright
• Try other PWM pins
• Multiple fading LEDs, at different rates
Sensors & Inputs
knife switch toggle switch(SPST) (SPDT)
Switches make or break a connection
Many sensors are variations on switches
Fundamentally, they’re all like the simple knife switchSingle pole = only one circuit is being controlledDouble pole = two circuits are being controlled at onceSingle throw = only one path for circuitDouble throw = two potential paths for circuit
Many Kinds of Switches
magnetic tilt leverhexidecimalTilt sensor has a little ball inside you can hear.Used to have mercury switches, with real metallic mercury inside. Not so much now tho’.Magnetic reed switches are cool, but delicate.The hex switch is actually many switches in one, and outputs 4 signals
Homemade Switches“Trick Penny”
Penny on a surface. When the penny is lifted, alarms go off
Homemade Switches“Trick Penny”
Surface is conductive metal sheet.Wire soldered to penny.Wire looped or crimped to metal sheet.
Homemade Switches“Smart Wind Chimes”
When the wind blows hard enough,you’re sent email
Should use stranded wire, not solid.Code analyzes series of on/off/on/off pulses to determine wind.
Digital Input
• Switches make or break a connection
• But Arduino wants to see a voltage
• Specifically, a “HIGH” (5 volts)
• or a “LOW” (0 volts)
How do you go from make/break to HIGH/LOW?
HIGH
LOW
From Switch to HIGH / LOW
• With no connection, digital inputs “float” between 0 & 5 volts (LOW & HIGH)
• Resistor “pulls” input to ground (0 volts)
• Pressing switch “pushes” input to 5 volts
• Press is HIGHNot pressed is LOW
Don’t want “pull-down” to be too small, or it uses a lot of current
Wiring it up
Let’s plug it into pin 2You can leave the last project on the board if you want.
Using digitalRead()
• In setup(): pinMode(myPin,INPUT) makes a pin an input
• In loop(): digitalRead(myPin) gets switch’s position
• If doing many tests, use a variable to hold the output value of digitalRead().
• e.g. val = digitalRead(myPin)
Enough with the atoms, back to the bits
Digital Input Sketch
Now you control the blinking
Load “Sketchbook/Examples/Digital/Button”
(How would you change it to blink the external LED you wired up?)Press to turn off, release to turn on.Notice it blinks the LED on-board the Arduino.Change the code to make it blink the pin 9 LED.
Using Switches to Make Decisions
• Often you’ll want to choose between actions, based on how a switch-like sensor
• E.g. “If person is detected, fire super soaker”
• E.g. “If flower pot soil is dry, turn on sprinklers”
• Define actions, choose them from sensor inputs
• Let’s try that with the actions we currently know
FadeOrBlinkLoad “FadeOrBlink” sketch from the handout
Combines “Blink” & “Fading” sketches into one, selected by
the button
Schematic is same as for “Fading” sketch
Battery Power
• First, program sketch into Arduino
• Unplug USB cable
• Change jumper from USB to EXT
• Plug in power (7-12VDC)
• Power LED lights up. It works!
• Reverse steps to reprogram
set to EXT
plug into
Vin & Gnd
Arduino can work totally stand-alone. It’s easy
Battery Power
• Plugging into the sockets is kind of fiddly
• Better to plug into the power jack
• Works great, but requires a little soldering
set to EXT
Center of jack is
positive
Going Further
• Make your own switches: aluminum foil, pennies, etc.
• Build a Knight Rider / Cylon scanning light
• Build a bike light that only works when you peddle
• Make an Annoy-a-Tron™ (blink-blink-blink, wait.... blink-blink-blink)
Lots of things you can do with just LEDs & switches
Tod E. Kurt
END Class 1
http://todbot.com/blog/bionicarduino/
Feel free to email me if you have any questions.
Resourceshttp://arduino.cc/
Official homepage. Also check out the Playground & forums
http://ladyada.net/learn/arduino/Great Arduino tutorials
http://todbot.com/blog/category/arduino/Various movies, hacks, tutorials on Arduino
http://freeduino.org/Index of Arduino knowledge
http://adafruit.com/Arduino starter kits, Boarduino Arduino clone, lots of cool kits
http://sparkfun.com/Sells Arduino boards and lots of neat sensors & stuff
Books:“Physical Computing”, Dan O’Sullivan & Tom Igoe“Making Things Talk”, Tom Igoe“Hacking Roomba”, Tod E. Kurt
obligiatory book plug
Bionic Arduino
Introduction to Microcontrollers with Arduino
Class 2
13 Nov 2007 - machineproject - Tod E. Kurt
What’s for Today• Random Behavior
• RGB LEDs
• Color mixing
• Analog input with variable resistors
• Potentiometers & photocells
• Basic serial input & output
• Playing sound with piezo buzzers
This is a lot of stuff, let’s see how far we get.
blink blink
compile
upload
sketch runs
TX/RX flashLoad “File/Sketchbook/Examples/Digital/Blink”
Recap: Blinky LEDMake sure things still work
Change the “delay()” values to change blink rate
Known Good Configuration
Rule #1 of experimenting:
Before trying anything new,
Get back to a known working state
So spend a few minutes & get “Blink” working again
Get your entire edit->compile->upload->run workingEven if it becomes so second nature to you that you feel you shouldn’t need to, do it anyway.Especially when mysterious problems arise, revert to a known state
Getting the Board Set Up
wire up pin 9 LED too
Arduinoboard
gnd
pin 9
gnd
resistor
LED
schematic
Questions / Review
Any questions, comments, or problems?
Aside: LED Light Tubes
Snug-fit straws on the end of your LEDs to make
them glow more visibly
I have a box of multi-colored straws for whatever color LED you like
Random Behavior“CandleLight”
Uses simple pseudo random
number generator to mimic flame
Use random(min,max) to pick a number between
min & max.
This sketch is in the handout.Can also use random numbers to make random decisions.Note: not truly random, but good enough for most purposes.
Analog InputTo computers, analog is chunky
image from: http://www.engr.colostate.edu/~dga/me307/lectures.html
Analog Input
• Many states, not just two (HIGH/LOW)
• Number of states (or values, or “bins”) is resolution
• Common computer resolutions:
• 8-bit = 256 values
• 16-bit = 65,536 values
• 32-bit = 4,294,967,296 values
Analog Input
• Arduino (ATmega168) has six ADC inputs
• (ADC = Analog to Digital Converter)
• Reads voltage between 0 to 5 volts
• Resolution is 10-bit (1024 values)
• In other words, 5/1024 = 4.8 mV smallest voltage change you can measure
Analog InputSure sure, but how to make a varying voltage?
With a potentiometer. Or just pot.
+5V–measure–
gnd–
50k
The pot you have
pots also look like this
PotentiometersMoving the knob is like moving
where the arrow taps the voltage on the resistor
When a resistor goes across a voltage difference, like +5V to Gnd, the voltage measured at any point along a resistor’s length is proportional to the distance from one side.
If you take apart a pot, there’s a little wiper just like in the schematic symbol.But I might have the directions reversed (clockwise vs. anti-clockwise).
What good are pots?
• Anytime you need a ranged input
• (we’re used to knobs)
• Measure rotational position
• steering wheel, robotic joint, etc.
• But more importantly for us, potentiometers are a good example of a resistive sensor
There are many kinds of resistive sensors
Arduino Analog Input
Two “legs” plug into +5V & Gnd(red + & blue -) buses
Middle “post” plugs into a row (row 7 here)
Run a wire from that row to Analog In 2
Plug pot directly into breadboard
Why are we using Analog In 2? Because it’s in the middle. There’s no reason, any of the 6 analog inputs would work the same.
Pot & LED Circuit
In schematics, inputs are usually on the left, outputs on the rightAlso, more positive voltages are on the top, more negative on the bottom
Arduinoboard
gnd
pin 2
+5V
+5V
gnd
50kpotentiometer
pin 9
LED
resistor220 (red-red-brown)
gnd
This is what your board should have on it now
Varying Brightness by Hand“PotDimmer”
Turn the knob to change LED brightness
process the input data
input
output
Most all embedded systems have a
input→process→output loop
Sketch available in handout
Two Ways toHook up LEDs
Arduinoboard
gnd
pin 9
gnd
resistor
LED
Arduinoboard
gnd
pin 9
resistor
LED
+5V+5V
To turn ON: digitalWrite(9,HIGH)
To turn OFF: digitalWrite(9,LOW) To turn OFF: digitalWrite(9,HIGH)
To turn ON: digitalWrite(9,LOW)
To set brightness: analogWrite(9,val) To set brightness: analogWrite(9,255-val)
We’ve been using the one on the left because it makes more sense.But you’ll see the method on the right as well.The reason for this is that some circuits can switch to Gnd better than they can switch to +5V.
RGB LEDsNormal LED
RGB LED
cathode –anode +
red cathode –
green cathode –
anode +blue cathode –
anode +
cathode –
anode +
bluered green
actually 3 LEDs in one package
RGB LED, aka “tri-color LED”Common-anode RGB LEDs are much more available than common-cathode.This is why we’re changing around the logic.
Color Mixing
Arduinoboard
pin 11
gnd
pin 10
pin 9220 (red,red,brown)
redgreen blue
+5V
common anode
RGB LED
With RGB you can make any color
(except black)
With just 3 LEDs you can make any* color
Mixing light is the additive color model(paint is subtractive color, and can give you brown)
*besides the additive/substractive color different, it’s hard to get the mix to be just right for a variety of annoying reasons:- the physics of LEDs mean that different color LEDs put out different amounts of light- our eyes respond non-linearly across the spectrum, i.e. we’re more sensitive to green than red- the lenses in most RGB LEDs don’t focus each color to the same spot
Laying out RGB LED Circuit
slightly bend the longest lead and plug it into the +5v (red) bus
plug remaining leads into rows (12,14,&16 here)
connect 220 (red-red-brown) resistors across middle to matching rows
run wires from resistors to pins 9,10,11 of Arduino, can color-code if you want
Arduinoboard
pin 11
gnd
pin 10
pin 9220 (red,red,brown)
redgreen blue
+5V
common anode
RGB LED
Ignore the green wire in the pictures, that’s another circuit.Keep the pot from last circuit if you can.
RGB Color Fading
“RGBMoodLight”
Slow color fading and mixing
Also outputs the current color values to the serial port
This sketch is located in the handout.We’ll get to the serial port stuff in a minute.
It just ramps up and down the red,green,& blue color values and writes them with analogWrite()from http://www.arduino.cc/en/Tutorial/DimmingLEDs
Pot-controlled RGB
Arduinoboard
pin 11
gnd
pin 10
pin 9220 (red,red,brown)
redgreen blue
+5V
common anode
RGB LED
pin 2
+5V
gnd
50kpot
Pot-controlled RGB
“RGBPotMixer”
Use the pot from before to control
the color mix
The code turns the single ranged input value into “sectors” where
each sector is a color
Also see “RGBPotMixer2” for a variation.How would you change it to adjust brightness?
Sensing the Dark• Pots are example of a voltage divider
• Voltage divider splits a voltage in two
• Same as two resistors, but you can vary them
Sensing the Dark: Photocells
• aka. photoresistor, light-dependent resistor
• A variable resistor
• Brighter light == lower resistance
• Photocells you have range approx. 0-10k-1M
schematic symbolPretty cheap too. Can get a grab bag of 100 misc from Jameco for $20
Photocell Circuit
pin A2
gnd
brown-black-orange
Try it with RGBPotMixer from before
Looks a lot like the pot circuit, doesn’t it?
Mood Light
Diffuser made from piece of plastic scratched with
sandpaper
Also, can use plastic wrap scrunched up to make an interesting diffuser.
Resistive sensors
thermistor(temperature)
flex sensor(bend, deflection)
photocell(light)
force sensors(pressure)
also air pressure and others
+5V
sensor
resistor
to analog input
circuit is the samefor all these
Thermistor image from: http://www.facstaff.bucknell.edu/mastascu/elessonsHTML/Sensors/TempR.htmlAlso see: http://www.ladyada.net/make/midisense/makesensor.html
Communicatingwith Others
• Arduino can use same USB cable for programming and to talk with computers
• Talking to other devices uses the “Serial” commands
• Serial.begin() – prepare to use serial
• Serial.print() – send data to computer
• Serial.read() – read data from computer
Can talk to not just computers. Most things more complex than simple sensors/actuators speak serial.
Watch the TX/RX LEDS
• TX – sending to PC
• RX – receiving from PC
• Used when programming or communicating
Arduino Says “Hi”“SerialHelloWorld”
Sends “Hello world!” to your computer
Click on “Serial Monitor” button to
see output
Watch TX LED compared to pin 13 LED
This sketch is located in the handout, but it’s pretty short.Use on-board pin 13 LED, no need to wire anything up.
Telling Arduino What To Do“SerialReadBasic”
You type “H”, LED blinks
In “Serial Monitor”, type “H”, press Send
Serial.available() tells you if data present to read
This sketch is in the handoutAlways check Serial.available() or if Serial.read() != -1 to determine if there’s actual data to read.
Can modify it to print “hello world” after it receives something, but before it checks for ‘H’.This way you can verify it’s actually receiving something.
Arduino Communications
• Psst, Arduino doesn’t really do USB
• It really is “serial”, like old RS-232 serial
• All microcontrollers can do serial
• Not many can do USB
• Serial is easy, USB is hard
serial terminal from the olde days
is just serial communications
Serial Communications• “Serial” because data is broken down into bits, each
sent one after the other down a single wire.
• The single ASCII character ‘B’ is sent as:
‘B’ = 0 1 0 0 0 0 1 0 = L H L L L L H L
=LOW
HIGH
• Toggle a pin to send data, just like blinking an LED
• You could implement sending serial data with digitalWrite() and delay()
• A single data wire needed to send data. One other to receive.
Note, a single data wire. You still need a ground wire.
Arduino & USB-to-serial
USB to serial
Arduino
microcontroller
Arduino board is really two circuits
Original Arduino boards were RS-232 serial, not USB.
Arduino MiniArduino Mini separates the two circuits
Arduino Mini Arduino Mini USB adapter
aka. “Arduino Stamp”If you don’t talk with a computer, the USB-to-serial functionality is superfluous.
Arduino to ComputerArduino boardLaptop
USB to serialArduino
microcontroller
USB to serial
driver
Arduino
programmer
Processing
sketch
Java program
RX
TX
-OR-
-OR-
-OR-
...
USBTX
RXchip
USB is totally optional for ArduinoBut it makes things easier
Original Arduino boards were RS-232 serial, not USB.All programs that talk to Arduino (even the Arduino IDE) think that they’re talking via a serial port.
Arduino & USB
• Since Arduino is all about serial
• And not USB,
• Interfacing to things like USB flash drives, USB hard disks, USB webcams, etc. is not possible
Also, USB is a host/peripheral protocol. Being a USB “host” means needing a lot of processing power and software, not something for a tiny 8kB microcontroller.It can be a peripheral. In fact, there is an open project called “AVR-USB” that allows AVR chips like used in Arduino to be proper USB peripherals. See: http://www.obdev.at/products/avrusb/
Controlling the Computer
• Can send sensor data from Arduino to computer with Serial.print()
• There are many different variations to suite your needs:
Controlling the Computer
In Arduino: read sensor, send data as byte
In Processing: read the byte, do something with it
You write one program on Arduino, one on the computer
But writing Processing programs is for later
• Receiving program on the computer can be in any language that knows about serial ports
• C/C++, Perl, PHP, Java, Max/MSP, Python, Visual Basic, etc.
• Pick your favorite one, write some code for Arduino to control
Controlling the Computer
If interested, I can give details on just about every language above.
Controlling Arduino, Again“SerialReadBlink”
Most control issues are data conversion issues
Type a number 1-9 and LED blinks that
many times
Converts typed ASCII value into usable number
This sketch is also in the handout
Serial-controlled RGB“SerialRGBLED”
Send color commands to Arduino
e.g. “r200”, “g50”, “b0”
g50
Sketch parses what you type, changes LEDs
This sketch is in the handout.Color command is two parts: colorCode and colorValuecolorCode is a character, ‘r’, ‘g’, or ‘b’.colorValue is a number between 0-255.Sketch shows rudimentary character string processing in Arduino.This is still one of the hardest tasks, unfortunately.
Reading Serial Strings
• The function “Serial.available()” makes reading strings easier
• Can use it to read all available serial data from computer
• The “readSerialString()” function at right takes a character string and sticks available serial data into it
Pay no attention to the pointer symbol (“*”)Must be careful about calling readSerialString() too often or you’ll read partial strings
Piezoelectrics
• Big word – piezein is greek for “squeeze”
• Some crystals, when squeezed, make a spark
• Turns out the process goes the other way too
• Spark a quartz crystal, and it flexes
• Piezo buzzers use this to make sound(flex something back and forth, it moves air)
Piezo buzzers don’t have quartz crystals, but instead a kind of ceramic that also exhibits piezoelectric properties.I pronounce it “pie-zoh”. Or sometimes “pee-ay-zoh”.
Piezo Buzzers
• Two wires, red & black.Polarity matters: black=ground
• Apply an oscillating voltage to make a noise
• The buzzer case supports the piezo element and has resonant cavity for sound
Oscillating voltage alternately squeezes and releases the piezo element.Must apply flucuating voltage, a steady HIGH or LOW won’t work.
diagrams from: http://www.maxim-ic.com/appnotes.cfm/appnote_number/988
What’s in a Piezo Buzzer?
You can get at the piezo element pretty easily.
Be careful not to crack the white disc that is
the actual piezo
Only take it out of its case to use it as a
sensor
another $1.99 I won’t be getting back from Radio Shack
Of course, you usually destroy the enclosure to get at the element.And it’s the enclosure that has the proper support and resonant cavity to make a loud sound
Piezo Buzzer
Arduinoboard
pin 7
gnd
+
–
piezobuzzer
Piezo leads are very thin. The breadboard holes grab them better than the header sockets, which is why the jumper leads are used.Or you can jam a jumper wire in the holes to hold in the piezo leads.
Play a Melody
“SoundSerial”
Play the piezo beeper with the Serial Monitor
Type multiple letters from “cdefgabC” to
make melodies
This sketch is in the handout,Notice the problem with this sketch?Different notes play for different amounts of time.50 cycles of low C isn’t the same amount of time as 50 cycles of high B
Making it QuieterEasiest way: add a resistor
(brown,
black,
orange)
Arduinoboard
pin 7
gnd
+
–
piezobuzzer
10k
Arduinoboard
pin 7
gnd
+
–
piezobuzzer
Like most things in electronics, if you want less of something, add a resistor.A better value would probably be 1k, but we don’t have that on hand.This may not seem important now, but wait for the next project.
Play a Stored Melody
“PlayMelody”
Plays a melody stored in the Arduino
Could be battery-powered, play melody on button trigger, control playback speed with photocell, etc.
Melody definition is sort of like the old cell ringtone styleMelody playing logic is a little hard to follow, since it is timing critical.
Make a Theremin
“ooo-weee-ooooo”
The original spooky sound machine
Works by measuring your body’s electric field
Leon Theremin
No touching needed!
We’ll use light in lieu of RF
As heard on Star Trek, Beach Boys, horror movies, Mars Attacks!, and bad New Age songs.Works sorta like those touch switches, but no touching here.That is, your body becomes a variable capacitor.
Light Theremin
“Theremin”
Move hand over photocell to change pitch
Play with val processing & cycles count to alter sensitivity, pitch and timbre
Okay so maybe it sounds more like a bad video game than a spooky movieThe glitchy sound is cause because of the time it takes to read the sensorThere are ways around such stuff, but requires more complex programming using timers & interruptsThe sound can get annoying quick
Other Serial Devices
to Wi-Fi to Ethernet to graphic LCDto 8-servo controller
Lantronix Wi-Port and Lantronix Xport http://lantronix.com/Seetron Serial Graphic display and Mini SSC http://www.seetron.com/slcds.htm http://www.seetron.com/ssc.htm
Serial Examples
to Roomba
You’ve already seen this. :)http://hackingroomba.com/
Going Further• Piezo buzzers
• Can hook up multiple buzzers for polyphonic sound
• Can play waves other than just square waves using PWM techniques
• Can also be used as input devices (we’ll cover that later)
Going Further• Serial communications
• Not just for computer-to-Arduino communications
• Many other devices speak serial
• Older keyboards & mice speak are serial(good for sensors!)
• Interface boards (graphic LCDs, servo drivers, RFID readers, Ethernet, Wi-Fi)
Going Further• RGB LEDS
• You can pretty easily replicate the Ambient Orb ($150) functionality
• Make a status display for your computer
• Computer-controlled accent lighting (a wash of color against the walls)
Ambient Orb doesn’t connect to computer though. Uses the pager network.Ambient Devices: http://www.ambientdevices.com/
Tod E. Kurt
END Class 2
http://todbot.com/blog/bionicarduino/
Feel free to email me if you have any questions.
Bionic Arduino
Introduction to Microcontrollers with Arduino
Class 3
18 Nov 2007 - machineproject - Tod E. Kurt
What’s for Today
• About DC motors
• Transistors as switches
• Controlling DC motors
• Introduction to Processing
• Controlling your computer with Arduino
• Piezo buzzers as sensors
In the handout thumbdrives, be sure to copy the Processing zip or dmg file for your OS.
blink blink
compile
upload
sketch runs
TX/RX flashLoad “File/Sketchbook/Examples/Digital/Blink”
Recap: Blinky LEDMake sure things still work
Change the “delay()” values to change blink rate
Class Kit 2 Contents“motors & motion”
Class Kit 2 Manifest
• Nintendo Wii Nunchuck
• Wii Nunchuck Adapter
• Large DC motor
• Small DC motor
• Small servo motor
• TIP120 power transistor
• 1N4001 power diode
• Several 500 ohm resistors (green-brown-brown)
• Couple of popsicle sticks
• Colorful pipe cleaners
“motors & motion”
DC Motors
come in all shapes and sizes
You probably have 3-4 on you right now
(cell vibrate, laptop fan, laptop dvd drive)
the two motorsin the kit
When motors first came out, people thought we’d just have one for the house. The household motor. Various attachments for vacuuming, meat grinding, ceiling fan were available, and some houses had intricate mazes of belts and gears routed through the house to supply this rotational power.
DC Motors
• direct-drive vs. gearhead – built-in gears or not
• voltage – what voltage it best operates at
• current (efficiency) – how much current it needs to spin
• speed – how fast it spins
• torque – how strong it spins
• oh, and also: size, shaft diameter, shaft length,etc.
A dizzying array of parameters specify a motor
The two motors you have are small direct-drive,high-efficiency motors that work at 5 volts
Gearhead motors are the best.
DC Motors Characteristics
• When the first start up, they draw a lot more current, up to 10x more.
• If you “stall” them (make it so they can’t turn), they also draw a lot of current
• They can operate in either direction, by switching voltage polarity
• Usually spin very fast: >1000 RPM
• To get slower spinning, need gearing
DC Motors
MDC motorbattery
polarity determines which way it rotates
To drive them, apply a voltageThe higher the voltage, the faster the spinning
Try this out real quick.Then swap polarity
Don’t let it go to long. These motors will work at 9V for awhile, but aren’t made to continuously run at that voltage.
DC Motors as Generators
M
DC motor
LED
Just as voltage causes rotation...
...rotation causes voltage
Try it out, but you have to spin really fast to get it to light (if LED doesn’t
light, try spinning the other direction)This is used for “regenerative
braking” in electric & hybrid cars
These high-efficiency motors I gave you don’t generate much current (because they don’t use much current). I have a cheapy motor that lights LEDs better that I can show you.
Transistors
TIP120
TIP120
base
collector emitter
base
collector
emitter
Act like switches
Turning on the “base” connects the “collector” & “emitter” together
schematic symbol
electricity flicks the switch instead of your finger
collector
emitter
base
how it kind of works
The differences between the pins are very important. The names aren’t that important, but their functions are. The “base” is the input that you use to open and close the “switch” across the “collector” and “emitter”. On this type of transistor (called an NPN), you need to make sure the collector is always more positive than the emitter. Generally you do this by connecting the emitter to ground.
Switching Motors with Transistors
M
DC motor
transistorresistor
battery
+ switch
M
DC motor
transistorresistor
+ switch
+
+
+
big powersource
transistors switch big signals with little signals
little motor big motor
switching a different power source
Need a “Kickback” Diode
M
DC motor
transistorresistor
battery
+ switch
diode
schematic symbol
line
since motors can act like generators,need to prevent them from generating “kickback” into the circuit
diode
Once a motor starts spinning, its inertia keeps it spinning, this turns it into a generator and thus can generate a “kickback” voltage. The kickback diode routes that voltage harmlessly back into the motor so it can’t damage the rest of the circuit.
Kickback is also called “back EMF” (EMF == electromotive force == voltage)
Controlling a Motor
Arduinoboard
gnd
pin 9
+5V
+5V
M
DC motor
TIP120500
1N4001
(green-brown-brown)
Can control speed of motor with analogWrite() just like controlling brightness of LED
start with the tiny motorb c e
b c
e
motor
Why 500 ohms? Because I have a lot of 500 ohm resistors. Typically you see 1k ohms. Anything 1k or below will work. The lower the value, the more current you’re “wasting” to turn on the transistor.
Wiring up Motor Circuittransistor turned around to make wiring easier
white diode line into +5V motor across diode
Arduinoboard
gnd
pin 9
+5V
+5V
M
DC motor
TIP120500
1N4001
(green-brown-brown)
e bc
b c
e
Sketch“SerialMotorSpeed”
Type a number 0-9 in Serial Monitor to control the speed of
the motor
How would you change this to control the motor speed
with the potentiometer?
Controlling a Bigger Motor
Arduinoboard
gnd
pin 9
+5V
+5V
M
DC motor
TIP120500
1N4001
(green-brown-brown)
+9V battery
Same circuit as before, different voltage source
Motor will spin faster for a given analogWrite() value
9V battery
motor w/ tape propellor
desk ding from motor getting loose
Actually with both of the motors you have, you can run off the Arduino power supply. But many motors cannot because they either draw too much current or they need a voltage higher than 5 volts.
Fun Motor Attachments
tape propellerpipe cleaner squigglerpopsicle stick beater
I’m terrible at mechanical engineering. If anyone has good ways of mounting things to motors, let me know. :-)
Wiring Up Bigger Motor
Don’t just add 9V to +5v bus!Move the diode from +5 to another rowAdd red 9V wire to that row,Add black 9V wire to Gnd
You might find it easier to push the red 9V wire in with the motor wire.
Can Switch Anything*
Arduinoboard
pin 7
gnd
1k
TIP120
1N4004
+5V
to load
5V relay
Just on/off, and a relay needs a diode too
to load: light bulb, car ignition, washing machine, etc.
Super bright LED light
Arduinoboard
gnd
pin 9
+12V+5V
TIP1201k
red LEDs
120
Relay switcher
*Anything up to about 1 amp. Need a bigger transistor or a relay after that
Full brightness control with PWM
Piezo Buzzer as Sensor
• Piezo buzzers exhibit the reverse piezoelectric effect.
• The normal piezoelectric effect is generating electricity from squeezing a crystal.
• Can get several thousand volts, makes a spark
• You probably have seen a big example of this already:
fireplace lighter
I have a demo piezo igniter from one of these lighters. It’s fun to shock yourself.Puts out several thousand volts. (ionization voltage of air =~ 30kV/cm)
Piezo Knock Sensor• To read a piezo you can
just hook it into an analog input, but:
• You need to drain off any voltage with a resistor, or it just builds up
• The protection diodes inside the AVR chip protect against the high voltage
piezo input schematic
Arduinoboard
analog pin 2
gnd
+
–
piezobuzzer
1M
(brown,
black,
green)
Note polarity of piezo still matters.If you’re doing this for real, you’d probably want to add an external protection diode, called a “zener diode”. It acts invisible until the voltage gets over its designed value (like 5 volts in this case), then it acts like a short circuit.
Wiring up Piezo SensorArduinoboard
analog pin 2
gnd
+
–
piezobuzzer
1M
(brown,
black,
green)
Could also plug it directly into the Arduino, might be easier because of those thin little wires on the piezo.
Piezo Knock“PiezoKnock”
Whack the piezo to print out a number based on force of
whack
Waits for input to go over threshold, then to drop below threshold
Number is “t”, the number of times it looped waiting for the value to drop below THRESHOLD.Notice how it doesn’t work quite right.
How Does that Work?
volts
time
piezo output voltage
whack!
threshold
t
• When a piezo is struck, it “rings” like a bell
• But instead of sound, it outputs voltage
• The sketch measures time above a certain voltage, hoping to catch largest ring
Depending on how fast you can watch the input, this technique works either really well or not that well. There are much faster ways of watching inputs that loops with analogRead()But for now it works okay
Custom Piezo SensorsCan mount the element on anything
(under rugs, floor mat, door, your body, etc.)
Here’s one glued to a larger brass disc for a drum trigger
You can get bare piezo buzzers (not in a black plastic enclosure) that you can mount on whatever you want.
Could make a MIDI Trigger
Uses piezos & buttons to send MIDI messages
Can trigger drum sounds or arbitrary sound samples
MIDIoutput
buttons
piezos
I used this during Halloween a few years ago to trigger scary sounds.
Or Trigger Actuators
Arduinoboard
analog pin 2
gnd
+
–
piezobuzzer
1M
(brown,
black,
green)
pin 9
+5V
M
DC motor
TIP120500
1N4001
(green,
brown,
brown)
If you still have your motor wired up
“PiezoMotorPulse”
Take a Break
Getting the Board Set Up
Wire up the potentiometer like from last week
Arduinoboard
gnd
pin 2
+5V
+5V
gnd
50kpot
And if you wire up an LED to pin 9, you can try out the “PotDimmer” sketch again to make sure things are wired up right.
Processing
• Processing makes Java programming as fun & easy as Arduino makes AVR programming
• Started as a tool to make generative art
• Is also often used to interface to devices like Arduino
• Think of it as a free Max/MSP
And it’s totally open source like Arduino.Processing GUI and Arduino GUI are from the same code, which is why it looks & acts similar.
Using Processing
• First, “install” Processing
• Load up “Examples » Topics » Motion » Bounce”
• Press “Run” button
• You just made a Java applet
The Processing application folders are in the handout, no installation is needed.Also try Examples » Topics » Motion » Collision. It’s a lot of fun.Notice how “Run” launches a new window containing the sketch.The black area at the bottom is a status window, just like in Arduino.
About Processing
• Processing sketches have very similar structure to Arduino sketches
• setup() – set up sketch, like size, framerate
• draw() – like loop(), called repeatedly
• Other functions can exist when using libraries
Processing & Arduino
• Processing and Arduino both talk to “serial” devices like the Arduino board
• Only one program per serial port
• So turn off Arduino’s Serial Monitor when connecting via Processing and vice-versa.
• Processing has a “Serial” library to talk to Arduino. E.g.:
serial communications
port = new Serial(..,“my_port_name”,19200)port.read(), port.write(), port.available(), etc.serialEvent() { }
The built-in serial library adds a new function you can use to your sketch: serialEvent()The serialEvent() function will get called whenever serial data is available.Or you can poll with port.available().
Processing Serialcommon Processing serial use
be sure to set to the same as “Serial Port” in Arduino GUI
1.
2.
3.
4.
four steps1. load library2. set portname3. open port4. read/write port
All you need to do talk to Arduino in Processing.The import statement says you want to do serial stuff.The “new Serial” creates a serial port object within ProcessingThen you can that object (or used the passed in one) to read from in the “serialEvent()” function
Arduino Talking to Processing
“PotSend”
Read knob,send it’s value
Note: doesn’t send the value as ASCII text, but as a binary byte
You can have 6 knobs totalbecause there are 6 Analog In pins
(BYTEs are easier to parse in Processing than other formats)
Meanwhile, back in Arduino, load up this sketch we’ll use with Processing
Processing + Arduino“ArduinoReadCircle”
The pot controls the hue of the onscreen circle
Arduino is running “PotSend”, repeatedly sending a number from
0-255 indicating knob position
This sketch is in the handout, under “processing_sketches”.
Another One“ArduinoBounce”
Every time a byte is received via the serial port, it alters the size of the ball to match.
Comment out the “background(102)” line to get trails
Uncomment the “fill()” line to get color trails
Notice the bug that happens when you change the size near a border.
And Another One“ArduinoPong”
The basics of a pong game.The pot controls paddle
position
Add another pot and a little more game logic and you have a 2-player game
These are all very minorly-modified examples of standard Processing sketches.
Triggering Sounds“ArduinoSounds”
Every time the piezo is knocked...a sound plays and a red disc appears
onscreen
This sketch needs the “minim” sound library.
You can add your own sounds (WAV or MP3)Hook a piezo up to your front door, and plug your computer into your stereo.Every time someone knocks on your door, a sound is played: a custom doorbell!
The zipfile for the “minim” library is in the handout, called “minim-1.1-lib.zip”.Unzip it and place the “minim” folder in the “Processing 0133/libraries” folder.
Adding Processing LibrariesUnzip, drop into “libraries” folder
drag
unzip open
Same for Windows and Mac OS X. Mac OS X shown.
Processing to Arduino“http_rgb_led”
Fetch a web page,get a color value from it, send the color to
Arduino with RGB LED
real quick
This is not to build, just quickly cover. It’s not in the handout, but,full details at: http://todbot.com/blog/2006/10/23/diy-ambient-orb-with-arduino-update/
Going Further
• DC motors
• Get some gearhead motors for serious torque or slower RPM
• Use Lego, Erector, Meccano to build mechanical linkages for motors
• Oh and you can now build a robot
Going Further
• Transistor switches
• Anytime you need to switch a signal more powerful than what Arduino can use
• These transistors switch up to 1 amp of DC voltage. For AC household currents, use transistor to switch a relay
• Can control just about anything in your house
Going Further
• Processing & Serial communications
• Processing can talk to the Net. It’s an Internet-to-Arduino gateway
• It can also talk to many computer peripherals, like video cameras
• Maybe: Arduino controls the motors, laptop controls the cameras of your robot
Tod E. Kurt
END Class 3
http://todbot.com/blog/bionicarduino/
Feel free to email me if you have any questions.
Bionic Arduino
Introduction to Microcontrollers with Arduino
Class 4
20 Nov 2007 - machineproject - Tod E. Kurt
What’s for Today
• About PWM
• Controlling Servos
• About the I2C bus
• Using I2C on Arduino
• About Accelerometers
• Nintendo Wii Nunchuck as Input Device
blink blink
compile
upload
sketch runs
TX/RX flashLoad “File/Sketchbook/Examples/Digital/Blink”
Recap: Blinky LEDMake sure things still work
Change the “delay()” values to change blink rate
Pulse Width Modulation
• More commonly called “PWM”
• Computers can’t output analog voltages
• Only digital voltages (0 volts or 5 volts)
• But you can fake it
• if you average a digital signal flipping between two voltages.
• For example...
PWM
0 volts
5 volts
50% 50% 50% 50% 50%
2.5 Volts
0 volts
5 volts
20% 80%
1.0 Volts
50%
20% 80% 20% 80%
0 volts
5 volts
75% 25%
3.75 Volts
75% 25% 75% 25%
output_voltage = (on_time / off_time) * max_voltage
Output voltage is averaged from on vs. off time
PWM• Used everywhere
• Lamp dimmers, motor speed control, power supplies, noise making
• Three characteristics of PWM signals
• Pulse width range (min/max)
• Pulse period(= 1/pulses per second)
• Voltage levels(0-5V, for instance)
width
period
height
You experienced a few applications of PWM already.
Servomotors
• Can be positioned from 0-180º
• Internal feedback circuitry & gearing takes care of the hard stuff
• Easy three-wire PWM 5V interface
(usually)
More specifically, these are R/C hobby servos used by remote control enthusiastsIn general, “servomotor” is a motor with an inherent feedback mechanism that allows you to send position commands to it without requiring you to do the position reading.
Servos are Awesome• DC motor
• High-torque gearing
• Potentiometer to read position
• Feedback circuitry to read pot and control motor
• All built in, you just feed it a PWM signal
With these little blue ones you have, you can see inside a bit at the internals of the servo.
Servos, good for what?
• Roboticists, movie effects people, and puppeteers use them extensively
• Any time you need controlled, repeatable motion
• Can turn rotation into linear movement with clever mechanical levers
Even clothes use servos now: http://www.technologyreview.com/read_article.aspx?id=17639&ch=infotech
Servos• Come in all sizes
• from super-tiny
• to drive-your-car
• But all have the same 3-wire interface
• Servos are spec’d by:157g
9g
weight: 9gspeed: .12s/60deg @ 6V
torque: 22oz/1.5kg @ 6Vvoltage: 4.6~6V
size: 21x11x28 mm
http://rctoys.com/http://hobbypeople.net/
Servo Mounts & Linkages
Lots of ways to mount a servo
And turn its rotational motion into other types of motion
mounting bracket: http://www.sierragiant.com/prod28.html
Servo Control
180º Power (+5V)Ground (0V)
Control (PWM)
• PWM freq is 50 Hz (i.e. every 20 millisecs)
• Pulse width ranges from 1 to 2 millisecs
• 1 millisec = full anti-clockwise position
• 2 millisec = full clockwise position
Servo Movement
0 degrees 90 degrees 180 degrees
1000 microsecs 1500 microsecs 2000 microsecs
In practice, pulse range can range from 500 to 2500 microsecs
(and go ahead and add a wire marker to your servo like the above)Put the red “arm” on your servo. Needs a philips screwdriver.Many commercial servo drivers have a calibration setting to deal with servo variability
Servo and ArduinoFirst, add some jumper wires to the servo connector
Gnd
Power
PWM control
I recommend matching the color coding of the wires as closely as possible
Servo and Arduino
Plug control wire to digital pin 7
Plug powerwires in
Moving a Servo
Move the servo acrossits range of motion
“ServoSimple”
Uses delayMicroseconds() for pulse width
Uses delay() for pulse frequency
Sketch is in the handoutCreated a custom function to handle making servo pulsesNew function “delayMicroseconds()”. Like “delay()”, but µsec instead of millisec.(and actually, just delaying 20 millisec is kinda wrong. should be: 20 - (pulsewidth/1000)(1000 microseconds = 1 millisecond, and 1000 milliseconds = 1 second)
Serial-controlled Servo
Takes the last servo example and adds our
standard serial input to it.
Drive the servo by pressing
number keys
“ServoSerialSimple”
Sketch is in the handout. Why that for loop? Because it takes time for the servo to get to a position and it has no memory.
Aside: Controlling Arduino
• Any program on the computer, not just the Arduino software, can control the Arduino board
• On Unixes like Mac OS X & Linux, even the command-line can do it:
demo% export PORT=/dev/tty.usbserial-A3000Xv0demo% stty -f $PORT 9600 raw -parenb -parodd cs8 -hupcl -cstopb clocal demo% printf "1" > $PORT # rotate servo left demo% printf "5" > $PORT # go to middledemo% printf "9" > $PORT # rotate servo right
Unix is rad.
Robo Cat Toy Idea
Tape on a pipe cleaner, and using random behavior similar to the “Candlelight”
sketch, make a randomly moving cat toy
Be sure to securely mount the servo before doing trial runs. Cats are good at taking apart prototype electronics.
Servo Timing Problems
• Two problems with the last sketch
• When servoPulse() function runs, nothing else can happen
• Servo isn’t given periodic pulses to keep it at position
• You need to run two different “tasks”:
• one to read the serial port
• one to drive the servo
If a servo is not being constantly told what to do, it goes slack and doesn’t lift/push/pull
Better Serial Servo
Works just like ServoSerialSimple
(but better)
Uses “millis()” to know what time it is
Update the servo when needed, not just when called at the right time
“ServoSerialBetter”
Sketch is in the handout.Trades memory use (the extra variables), for more useful logic.Can call updateServo() as often as you want, servo is only moved when needed.
Multiple Servos
• The updateServo() technique can be extended to many servos
• Only limit really is number of digital output pins you have
• It starts getting tricky after about 8 servos though
Multiple “Tasks”
• Define your task
• Break it up into multiple time-based chunks (“task slices”)
• Put those task slices in a function
• Use millis() to determine when a slice should run
• Call the functions from loop()
The concept inside updateServo() is useful anytime you need to do multiple “things
at once” in an Arduino sketch:
Inside your task slices, avoid using delay(), for loops, and other code structures that would cause the code to stay inside a task for too longThis is called “cooperative multitasking”, and it’s how OSs in the 80s worked.
Arduino PWM
• Arduino has built-in PWM
• On pins 9,10,11
• Use analogWrite(pin,value)
• It operates at a high, fixed frequency(thus not usable for servos)
• But great for LEDs and motors
• Uses built-in PWM circuits of the ATmega8 chip -» no software needed
why all the software, doesn’t Arduino have PWM?
The PWM speed used for analogWrite() is set to 450Hz or 30 kHz currently. I forget which, but it’s not something changeable without understanding more about how AVRs work.So when programming AVRs in C outside of Arduino, PWM speed can be set to just about any value.
Take a Break
Serial Communication
Separate wires for transmit & receive
Asynchronous communication
asynchronous – no clockData represented by setting HIGH/LOW at given times
Synchronous communication
Synchronous – with clockData represented by setting
HIGH/LOW when “clock” changes
A single clock wire & data wire for each direction like before
Device A Device B
TX
RX
RX
TX
Device A Device B
clockdata A->Bdata B->A
Each device must have good “rhythm” Neither needs good rhythm, but one is the conductor
Is one better than the other? It depends on your application. Async is good if there are only two devices and they’re both pre-configured to agree on the speed (like your Arduino sketches)
Synchronous is generally better for faster speeds (because you don’t need an accurate clock, just the ability to watch the clock wire).
I2C, aka “Two-wire”
Masterdevice
Peripheral device 1
Peripheral device 2
Peripheral device N
• • •
dataSDA
clockSCK
Synchronous serial bus with shared a data line
• Up to 127 devices on one bus• Up to 1Mbps data rate• Really simple protocol (compared to USB,Ethernet,etc)
• Most microcontrollers have it built-in
a little network for your gadgets
The shared data line means the devices have to agree on when they should “talk” on it. Like how on CBs you say “over” and “over & out” to indicate you’re finished so the other person talk.
See “Introduction to I2C”: http://www.embedded.com/story/OEG20010718S0073“I2C” stands for “Inter-Integrated Circuit”, but no one calls it thatAnd if your microcontroller doesn’t have I2C hardware built-in, you can fake it by hand in software (for master devices anyway)
Many I2C devices
touch sensor compass
fm transmitter
non-volatile memory
LCD displaytemperature & humidity sensor
And many others(gyros,keyboards, motors,...)
Images from Sparkfun.com,except LCD from matrixorbital.com
Obligatory BlinkM PromoI2C Smart LED
Does all the hard PWM & waveform generation for youYou should be able to buy these from Sparkfun.com in a month or so.
Nintendo Wii Nunchuck
• Standard I2C interface
• 3-axis accelerometer with 10-bit accuracy
• 2-axis analog joystick with 8-bit A/D converter
• 2 buttons
• $20
If you look at the architecture for the Nintendo Wii and its peripherals, you see an almost un-Nintendo adherence to standards. The Wii controllers are the most obvioius examples of this. The Wii controller bus is standard I2C. The Wii remote speaks Bluetooth HID to the Wii (or your Mac or PC)
Because it uses standard I2C, it’s easy to make the Nunchuck work with Arduino, Basic Stamp or most other microcontrollers.
See: http://www.wiili.org/index.php/Wiimote/Extension_Controllers/Nunchukand: http://www.windmeadow.com/node/42and: http://todbot.com/blog/2007/10/25/boarduino-wii-nunchuck-servo/
And then there’s the Wii Remote, besides Bluetooth HID, it also has accelerometers, buttons, speaker, memory, and is I2C master.
Accelerometer?• Measures acceleration
(changes in speed)
• Like when the car pushes you into the seat
• Gravity is acceleration
• So, also measures tilt
horizontal tilt right tilt left
Nunchuck Accelerometer
XZ
Y
Wii Remote & Nunchuck accelerometer axes
I’m not sure if I have the Nunchuck one right.
Wiimote axis image from http://www.wiili.org/index.php/Wiimote
I2C on Arduino
• I2C built-in on Arduino’s ATmega168 chip
• Use “Wire” library to access it
• Analog In 4 is SDA signal
• Analog In 5 is SCK signal
SDA
SCK
Arduino “Wire” libraryWriting Data
Start sending
Join I2C bus(as master)
Send data
Load Wire library
Stop sending
And what the various commands do are documented in the instructions / datasheet for a particular device.
Arduino “Wire” libraryReading Data
Request data from device
Join I2C bus(as master)
Get data
What kinds of interactions you can have depends on the device you’re talking to
Most devices have several “commands”
And what the various commands do are documented in the instructions / datasheet for a particular device.
Wiring up the NunchuckWe could hack off the connector
and use the wires directly
But instead let’s use this little adapter board
Wii Nunchuck Adapter
SCK GND
+V SDAn/c
n/c
Nunchuck Pinout
(looking into Nunchuck connector)
Adapter Pinout
+V SCK
SDAGND
Note there *are* labels on the adapter, but they’re wrong. So you’ll have to trust the diagrams above
Wiring it Up
GND SDA+5V SCK
SDA (pin 4)
SCK (pin5)
Pluggin’ in the ‘chuck
Trying the Nunchuck“NunchuckPrint”
Read the Nunchuck every 1/10th of a second & print out all the data:- joystick position (x,y)- accelerometer (x,y,z)- buttons Z,C
XZ
Y
Uses the beginnings of an Arduino library I’m writing.
Adding a Servo
Move the servo by moving your arm
“NunchuckServo”
You’re a cyborg!
Also press the Z button to flash the pin 13 LED
Utilizes the task slicing mentioned before
Nunchuck Servo
Twist the nunchuck
and the servo matches your
movement
Segway Emulator
Same basic code as NunchuckServo.For details see: http://todbot.com/blog/2007/10/25/boarduino-wii-nunchuck-servo/
Going Further
• Servos
• Hook several together to create a multi-axis robot arm
• Make a “servo recorder” to records your arm movements to servo positions and plays them back
• Great for holiday animatronics
Going Further
• I2C devices
• Try out some other devices
• Just string them on the same two wires used for the Nunchuck
• Cooperative Multitasking
• Try making a theremin with nunchuck & piezo
• See if previous examples can be made more responsive
Going Further
• Nunchuck
• It’s a freespace motion sensor. Control anything like you’re waving a magic wand!
• What about the joystick? We didn’t even get a chance to play with that
• Alternative input device to your computer: control Processing, etc.
SummaryYou’ve learned many different physical building blocks
LEDs
switches/buttonsresistive sensors
motors
piezos
servos
XZ
Y
accelerometers
SummaryAnd you’ve learned many software building blocks
pulse width modulation
serial communication
digital I/O
analog I/O
data driven code
frequency modulation
multiple tasks
I2C
Summary
Hope you had fun and continue playing with Arduino
Feel free to contact me to chat about this stuff
Tod E. Kurt
END Class 4
http://todbot.com/blog/bionicarduino/
Feel free to email me if you have any questions.