Introduction to Microcontrollers

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Introduction to Microcontrollers

• And all that whirrs, clicks, and beeps

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Instructors

• Ms. Hinterlong
• Lucas Sturnfield
• Brian Baker
• Thomas Houlahan

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Sponsors

• Houlahans Tavern and Grill

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Programming Languages

• .NET, Java, C, Python? Assembly?

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what Micros can do
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Electronics

• Electron juggling and shuffling
• (some kinds of shuffling are more impressive than
  others)

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Outline

• Today
• Basic electronics
• Digital electronics
• Tuesday
• Programming a microcontroller
• Start projects
• Wednesday
• Projects
• Thursday
• Projects
• Friday
• Projects and presentations

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Basic Electronics
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Basic Electronics - Circuits
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Circuit Diagrams
http//www.fancon.cz/slave-flash-trigger/slave-fla
sh-en.html
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Wire and Elements
Some elements
Elements wired together
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Branches and Nodes
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Branches and Nodes
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Branches and Nodes
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Voltage and Current

• Voltage
• Potential energy per unit charge
• Measured in Volts
• Joules per Coulomb
• Water analog pressure
• Measured between nodes

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Voltage and Current

• Current
• Flow of electrons
• Measured in Amperes (Amps)
• Coulombs per Second
• Water analog flow rate
• Measured through an branch (through an element)

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Ohms Law V I R

• Voltage across the element Va Vb
• Resistor has resistance R1, measured in Ohms
• Current through resistor is i_R1
• Va-Vb R1 i_R1

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Power P V I

• Power used by any branch is equal to the voltage
  across the branch multiplied by the current
  through that branch
• Units Joules / Coulomb Coulomb / Second
  Joules / Second Watts

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KVL and KCL

• Kirchoffs Voltage Law
• The sum of voltages around any loop equals zero

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KVL and KCL

• Define a ground node to be zero volts
• Now, each node has a voltage

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KVL and KCL

• Kirchoffs Current Law
• The sum of currents entering a node equals zero
• (a lot like mass conservation)

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Breadboards

• Internal connections
• Power rails

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Multimeters Measuring Voltage

• Multimeter must connect to circuit differently to
  measure voltage or current
• To measure voltage, set multimeter to Voltage
  setting, and place leads in parallel with branch
  of interest

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Multimeters Measuring Current

• To measure current, set multimeter to Current
  setting, and place leads in series with branch of
  interest

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Series and Parallel Resistance
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Diodes and LEDs

• Water analog Check valve only lets current
  flow one way
• Either ON or OFF
• On
• Anode-cathod voltage is fixed value, no matter
  what current (0.7 V)
• Off
• Current is zero, no matter what voltage
• LEDs emit light when ON

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LEDs and Current Limiting Resistors
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Recap

• Voltage is potential energy (pressure)
• Current is flow of electrons (flow rate)
• Voltage is measured between nodes, or with
  respect to ground
• Current is measured through branches
• VIR
• PIV

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Voltage isnt always Constant

• Speakers are driven by a voltage signal settings
  the voltage sets the position of the speaker
  diaphragm

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Sensors and analog out

• Some sensors vary an output voltage the voltage
  corresponds to a sensor value
• Maxbotix ultrasonic sensor outputs voltage
  corresponding to distance

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RF - radio

• Radio uses Electromagnetic waves
• Voltage on antenna varies
• Waveform carries data

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Power DC vs AC

• DC

• AC

• Direct Current
• Batteries, wall warts
• Time-constant voltage
• Current flows one way

• Alternating Current
• Electrical outlets
• Time-varying voltage
• Current flows different ways at different times
• Transfers power great distances with low line loss

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AC to DC
http//hyperphysics.phy-astr.gsu.edu
LM7805 Volage regulator - takes 9V DC, makes 5V
DC
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Capacitor

• Stores energy
• Resists change in voltage
• Electrolytic are polarized, have stripe on minus
  end
• Capacitance is measured in Farads (typically,
  micro Farads)

Electrolytic capacitor
Ceramic capacitor
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Transistor

• Considered by many to be greatest invention of
  the 20th century
• Transistor as amplifier (radio)
• Transistor as switch

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Digital Electronics

• 01101000011001010110110001101100011011110010000001
  11011101101111011100100110110001100100
• (hello world)

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1 and 0

• Digital logic doesnt use analog voltages only
  high and low have meaning
• Typically 5V and 0V
• Sometimes 3.3V and 0V
• Computer processor
• High is 1, Low is 0

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Microcontroller

• Programmable Chip
• Same idea as PC, but on much smaller scale

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Black Box

• Black box does stuff to inputs to get outputs
• Typically dont want to care what happens inside
  black box just need to know how to give it
  input, and what output to expect

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Black Box

• Need to know where to put toast
• Need to know to be careful getting toast its
  hot
• Need to know that ding means toast is done
• Ding is an output!
• Power, timer setting, lever are all inputs

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Computer vs Microcontroller

• Computer

• Microcontroller

• Inputs
• Keyboard
• Mouse
• Microphone
• Outputs
• Monitor
• Speakers
• Black box
• Program is written on the computer

• Inputs
• Voltage on pins
• Outputs
• Voltage on pins
• Black box
• Program is written on a computer and downloaded
  to the chip

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Why Microcontrollers?

• Low cost for a lot of processing
• Low power (can run on batteries)
• If power is well managed, can run for years on a
  9V!
• Small
• Can communicate with PCs to do complex processing
  with real world effects

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Blinky LED in a Breadboard

• Breadboard stuff
• PICS are already programmed
• Remember Electrolytic caps are polarized stripe
  goes to lower voltage
• When you apply power, LED should blink

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PCB

• Haha! jk jk we have awesome pcb.
• Lets solder
• Soldering irons get HOT dont burn yourself
• Tinning things put a little solder on both
  pieces that youll connect, THEN connect them
• Sockets are done you get to do caps and 7805
• With sockets, we dont apply heat to a chip.
  Also, if the chip gets fried, we can pull it and
  put a new one in
• Test with Blinky LED again

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Introduction to Microcontrollers
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Programming a PIC

• Making machines Think

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Architecture

• Memory
• Variables registers all 1 byte big
• F register
• Declare you own
• Special ones, like PORTD and TRISB
• Working register the accumulator your hands
• Instructions
• Processor only does ONE thing at time moves
  from one instruction to the next
• Each instruction has an opcode (action) and
  parameters
• i.e., movfw PORTA

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Config Variables

• Comments prefixed with semilcolons
• Compiler info
• Config bits
• Constants
• Variables declared two different ways

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Beginning of Code

• ORG declares a place in code memory
• 0x000 is restart
• 0x004 is interrupt
• (ignore interrupt for now)
• Now every line is a comment, label, or
  instruction
• nop do nothing
• goto label jumps to a named label

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Initialization

• bcf and bsf bit modification
• Special f registers and bank bits
• Moving through accumulator
• PORT and TRIS control pins
• ADCON1 and analog

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The Actual LED Blinking Code

• Turn it on
• Wait using a subprocedure (goto and return)
• Turn it off
• Wait using sub
• Loop back main program loops

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The Delay Subprocedure

• Some calculated exact cycle usage (its
  deterministic depends on clock frequency!)
• Involves looping and counting down a bunch
  takes a lot less room than 5000000 nop
  instructions!
• Note return statement
• END statement is end of our code
• Branching no IF decfsz (also, btfss/btfsc)

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Adding a Button

• We have processing and output, lets add an input

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Debouncing

• Voltage doesnt switch all that cleanly
• Our PIC is faster than the debounce!
• Solutions
• Hardware add a capacitor to filter
• Software poll button again a set time after it
  first changes

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Code changes

• TRISB bit 0 should be 1 for an input!
• movlw b00000001
• movwf TRISB
• Completely different loop
• New (shorter) delay functions (please excuse the
  messy code!)
• Well have the PIC turn LED at PORTD,7 on or off
  when pressed, like a lightswitch

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Button Loop

• Check to see if button changes if it does, go
  to double check
• doubleCheck waits about 2ms and then checks
  button again. If not pressed, go back, if
  pressed, go on
• setLED or clearLED depending on LED state
• Then, wait for button release before checking for
  another button press

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Programming the PIC

• Compile

• Download

• Project -gt Build All (F10)
• Can has Build Succeeded?
• Dont need to download each time compiling can
  help you find errors

• If its the only option
• Programmer-gt
• -gt Select Programmer
• -gt PICkit 2
• Then,
• Plug in PICkit 2 to header
• Programmer-gt
• -gt Program

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Debugging

• The PIC is a really good black box
• You dont get info out of it unless you code it
  to output info!
• LEDs can be useful for tracking what state the
  PIC is in
• For more complex info, communication with a
  computer is the way to go

Extra credit for laughing at my visual puns!
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Serial/COM/UART/RS232

• Uses 9 pin connector
• Only 3 are used Gnd, Rx, Tx
• Many new computers dont have this connector
• USB to Serial adapter are widely available
• PIC has built in module for this (UART)
• Libraries for Serial
• Hyperterminal

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Serial Communication Computer side

• Serial ports show up as COM ports (COM1, COM2,
  etc)
• You can write your own programs
• Hyperterminal is easy to use for simple things
  (including debugging)
• ASCII table

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Serial Communication Computer side

• Name connection
• Select COM Port
• Settings
• 9600 baud is commonly used
• To see what you type,
• File -gt Properties
• ASCII Setup button
• Check Echo typed characters locally

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Serial Communication PIC side

• RS232 standard
• 1 is -12V, 0 is 12V
• We usually just want or have 5V supply, not 24V
  split in the middle!
• MAX232 handles inversion and voltage boosting

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Serial Code

• Enabling Serial communication on the 877a is a
  matter of setting up the associated f-registers.
  SPBRG stores a value that corresponds to 9600
  baud, enable bits are set, etc
• Documentation for how to do this (for other
  modules, too) is in the 877a datasheet

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Serial Code

• To transmit, load a value into TXREG
• Values for ASCII letters can be found at
  asciitable.com
• Before transmitting again, wait for transmit to
  finish with waitForTX
• To receive, call waitForRX it puts received
  value into w (and variable rxData)
• Be careful using it stops everything until a
  character is received!
• There are other ways to deal with this

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ALU

• Arithmetic Logic Unit
• Handles instructions like addwf, subwf, incf,
  decf, rrf, rlf, etc
• After performing operation, some bits in in
  STATUS might change Z, C, DC
• If Z is set, result was zero
• If C is set, carry occurred (or, for a situation
  where a borrow might occur, 0 if the borrow
  occurred)
• Also stores bits that fall off from rrf and rlf

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ALU

• To test if two things are equal,
• movfw thing1
• subwf thing2, w make sure result is stored in
  w!
• btfss STATUS, Z
• goto not_equal
• goto equal
• rrf and rlf are rotate right and rotate left
  through carry
• Always bcf or bsf STATUS, C before doing rrf or
  rlf!

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Components

• A part bin fit for Frankenstein

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Three Categories
Inputs (Sensors) Outputs Processing
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Communication

• These inputs and/or outputs
• RF
• Sparkfun has some modules
• Bluetooth
• Appear as COM port on computer
• Sparkfun
• Current wireless protocol, devices for cell
  phones (Android!)
• -
• RFID
• TINY circuits, powered by antennae
• Not all standardized
• Implants
• Key cards

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Sensors - Light

• Photocells
• Resistance decreases with more light
• IR Receivers
• Communication
• Coupled with IR LEDs, can do rangefinding
• PIR Motion Sensing
• CCD Cameras

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Sensors - Potentiometers

• Variable resisters
• Depending on controls position, resistance
  changes
• Usually have a split design 3 pins. Resistance
  from 1 to 2 plus that from 2 to 3 is always the
  same put power at 1 and 3, and voltage at 2
  varies

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Sensors - Ultrasonic

• Maxbotix makes easy to use ultrasonic
  rangefinders
• Different sensitivities
• Can be daisy-chained
• Analog, Serial, and Pulse-width outputs
• 30 each

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Sensors - Temperature

• Thermocouple
• Voltage corresponds to temperature
• Cheap, standardized
• - Nonlinear!
• Maxim OneWire
• Actually pretty complicated
• Can set alarm temps, 0.5 degrees C resolution

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Sensors - Buttons

• Tact switches
• Cheap! Standardized
• - Small, not pretty
• Keypads
• Can look awesome
• - Weirder to interface with
• Videogame controllers
• Can wire directly to buttons, analog sticks
• PS2 interface is known

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Sensors - Wiimote

• Communicates with Bluetooth
• Computer drivers have been developed
• Even better, Nunchuck uses I2C
• 3-axis accel, analog stick, and two buttons for
  20
• PCB interface available (FunGizmos.com)

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Sensors Accelerometers and Gyroscopes

• There are MEMS Gyroscopes
• small, interface with electronics easily
• -
• Used together, accels gyroscopes provide data
  to do position tracking
• Theres some drift
• Some serious number crunching needs to be done to
  track in real time

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Sensors - GPS

• Tons of fun data!
• - Ceiling interferes, and
• (They DID pay to put a bunch of satellites in
  orbit)
• (Plus they crunch a lot of numbers)

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Sensors Touchpads, Mice, Keyboards

• Lots of Multitouch interfaces
• Mice Keyboards PS2 interface

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Sensors - Other

• Alcohol Gas
• Barometric
• If you look hard enough, youll probably find
  what youre looking for
• Mic voice recognition - SAPI
• Cameras Computer Vision - OpenCV

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Outputs On/Off

• Simply turning things on and off can be an output
• Triacs for controlling 120V AC
• Working with 120V AC is MUCH MORE DANGEROUS
  never work on a live circuit
• Brian used MAC15A8 triacs, and MOC3012 / NTE3047
  drivers
• Transistors for DC
• NPN goes at bottom, PNP goes at top

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Ouputs LEDs and 7 Segment LCDs

• LEDs are fun
• Cheap!
• Add a coin cell battery, a magnet, and some
  scotch tape, and you have an LED throwie
• Developed by Graffiti Researh Lab
• EL wire
• Electroluminescent wire
• Requires a special driving inverter, but whole
  wire lights up
• 7-Segs
• Very commonly used, pretty cheap
• Really just a bunch of LEDs
• Driver ICs are available put in a number, it
  displays it

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Outputs Character Graphic LCDs

• Character LCDs
• A little more complicated, but great for
  displaying info
• The blue ones look cool
• Graphic LCDs
• Abundant, because of cell phones
• Much more complicated to work with, but much more
  possibility
• Some dude had an AVR micro displaying very basic
  3D graphics

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Outputs - Projectors

• Pretty much necessitates a computer, but can do
  cool things
• GRLs laser pointer graffiti

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Outputs Buzzers, Peltier, Others

• Piezoelectric buzzer
• Very very common
• Speakers
• Peltier heater/cooler
• Apply power one direction, and one side gets
  cool, the other gets hot
• Apply power the other way, first side gets hot
  and second gets cool
• Vibration Motors
• DC motor with off-center weight on shaft
• Pneumatics Hydraulics
• Electrically controlled valves

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Output Regular DC Motors

• You set POWER, which corresponds to SPEED, with a
  constant load
• Apply power one way, and they turn that way.
  Apply power the other way, they turn the other
  way
• Geared DC are often desired without gearing, the
  motors have high speed but VERY low torque
• Setting direction electronically requires a
  circuit called an
• H-Bridge

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Output Servos and Steppers

• Servo motors
• You set ANGLE
• Less than 360 degree swing
• 3 pins power, ground, and analog voltage
  corresponding to angle (can use PWM)
• Stepper motors
• You set POSITION
• Continuous rotation
• More complicated to drive must step pins in a
  sequence, i.e. 0001 to 0011 to 0010 to 0110 to
  0100 etc
• Separate driver ICs are available

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Processing

• Optoisolators
• EEPROM
• Extra data storage
• Usually has I2C interface
• SD cards are apparently decently easy to
  interface with, too
• Shift Registers
• Extra IO pins
• Use 2 or 3 pins on micro to control 8 pins on
  shift register. Daisy chain to control 16, 24,
  etc
• Tradeoff is speed changing even one pin takes
  time to set them all
• 7 Seg drivers
• Give it a number, it turns on correct LEDs in 7
  seg
• H-Bridge
• Given logic inputs and power inputs, can connect
  a pin to power or ground
• Needed because a single transistor just connects
  the pin to power or nothing (or, alternatively,
  ground or nothing)

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Processing

• Stepper drivers
• Provide power, tell it to step one direction or
  the other, it handles the rest
• PWM chips
• Provides more PWM channels
• DACs and ADCs
• ADC common on PICs, but DAC isnt. PWM can be
  used to approximate
• And/Or/Not gates
• Very basic logic circuits useful in some
  situations to save IO pins (Chalkzilla example)
• 555 timers
• By choosing different resistors and capacitors to
  hook up to it, you can set the pulse width, pulse
  delay, etc
• Op-Amps
• These are a big deal
• All sorts of analog magic amplification,
  subtraction, addition, derivatives, integrals,
  isolation
• Beyond the scope of this. Take Electronics at
  IMSA!

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Projects