1. Week 6: Style and Peripherals
Bryan Burlingame
27 September 2017

2. The Plan for Today
Discuss peripherals on the Experimenter & the Arduino
Discuss programming style
Homework 3 due. Homework 4 due Oct 11
Extra Credit
Due in two weeks (5 exam points)
Find an academic journal article related to this class and write a one page response (not a synopsis!) to the article
Had planned to talk about blocking and non-blocking code and debouncing switches.

3. Learning Objectives Discuss the importance of style in code
Define scope and variable duration

4. Programming Style
The layout of program directives using white space, syntax, & punctuation to visually highlight a programmer’s intention
Good Style is
Consistent – A given structure always looks the same
Illustrative – The intent of the code is shown by the grammar
Clear – Any reasonable programmer should be able to follow the intent

5. Programming Style Why does it matter?
Reduces bugs – the human eye is excellent at detecting patterns
Reduces development time
Allows others to understand how to approach your code
Style is a fundamental part of code documentation
9 different style documented

6. No style
#include "stdio.h" #include "math.h" int main() { double time, max_height, velocity_at_apex, time_at_apex,height,velocity = 0; printf( "%4s %10s %14s\n", "time", "height (m)", "velocity (m/s)" ); printf( "%4s %10s %14s\n", "----", " ", " " ); for( time = 0.0; time < 49.0; time = time ) { height = * pow( time, 4.0 ) * pow( time, 3.0 ) ; velocity = (-0.48 * pow( time, 3.0 ) * pow( time, 2.0 ); if( height > max_height ) { max_height = height; velocity_at_apex = velocity; time_at_apex = time; } } printf( "Max height %.2lf, at %.3lf hours, while moving %.3lf m/s\n",max_height, time_at_apex, velocity_at_apex); return(0); }

7. Student Style
#include "stdio.h" #include "math.h" int main() { double time, max_height, velocity_at_apex, time_at_apex,height,velocity = 0; printf( "%4s %10s %14s\n", "time", "height (m)", "velocity (m/s)" ); printf( "%4s %10s %14s\n", "----", " ", " " ); for( time = 0.0; time < 49.0; time = time ) { height = * pow( time, 4.0 ) * pow( time, 3.0 ) ; velocity = (-0.48 * pow( time, 3.0 ) * pow( time, 2.0 ); if( height > max_height ) { max_height = height; velocity_at_apex = velocity; time_at_apex = time; } } printf( "Max height %.2lf, at %.3lf hours, while moving %.3lf m/s\n",max_height, time_at_apex, velocity_at_apex); return(0);

8. K&R Style
#include "stdio.h" #include "math.h" int main() { double time = 0; double max_height = 0; double velocity_at_apex = 0; double time_at_apex = 0; double height,velocity = 0; printf( "%4s %10s %14s\n", "time", "height (m)", "velocity (m/s)" ); printf( "%4s %10s %14s\n", "----", " ", " " ); for( time = 0.0; time < 49.0; time = time ) { height = * pow( time, 4.0 ) * pow( time, 3.0 ) ; velocity = (-0.48 * pow( time, 3.0 ) * pow( time, 2.0 ); if( height > max_height ) { max_height = height; velocity_at_apex = velocity; time_at_apex = time; } printf( "Max height %.2lf, at %.3lf hours, while moving %.3lf m/s\n",max_height, time_at_apex, velocity_at_apex); return(0);

9. Allman Style/BSD Style
#include "stdio.h" #include "math.h" int main() { double time = 0; double max_height = 0; double velocity_at_apex = 0; double time_at_apex = 0; double height,velocity = 0; printf( "%4s %10s %14s\n", "time", "height (m)", "velocity (m/s)" ); printf( "%4s %10s %14s\n", "----", " ", " " ); for( time = 0.0; time < 49.0; time = time ) height = * pow( time, 4.0 ) * pow( time, 3.0 ) ; velocity = (-0.48 * pow( time, 3.0 ) * pow( time, 2.0 ); if( height > max_height ) max_height = height; velocity_at_apex = velocity; time_at_apex = time; } printf( "Max height %.2lf, at %.3lf hours, while moving %.3lf m/s\n",max_height, time_at_apex, velocity_at_apex); return(0);

10. Recall: Definition of a Microcontroller
A microcontroller is an integrated circuit which combines:
Microprocessor
Memory
Input/Output Peripherals
Ex: Serial console, digital to analog converters

11. Arduino Peripherals (Uno)
Serial (TTL)
6 PWM modules (Digital to Analog (DAC))
6 ADC (Analog to Digital)
SPI bus
TWI (I2C) bus

12. Experimenter Red/Green/Blue (RGB) Light Emitting Diode (LED)
4 x Red LEDs
4 x Active low switches
Servoelectric motor header (servo)
Piezo-electric speaker (piezo)
Potentiometer (POT)
Photocell resistor
Temperature sensor

13. Spartronics Experimenter Digital Pin Assignments13 12 11 10 9 8 7 6 5 4 3 2 1
SCK
MISO
MOSI SS
OC1
ICP
AIN1
AIN0 T1 T0
INT1
INT0
TXD
RXD
LED
pwm
LED0
LED1
LED2
LED3
red
green
blue
piezo
servo
SW0
SW1
SW2
SW3
Piezo rectangle is hyperlinked to an image of the actual Experimenter board. The piezo speaker is hyperlinked back to this slide.

14. Digital Signals Most basic form of sending information to the world
On or Off (1 or 0)
Active High Logic
Think of a light

15. Experimenter Switches
Active Low
Unpressed, 5V (HIGH)
Pressed, Ground 0V (LOW)
A pull-up resistor is required
The Arduino has them as a peripheral
Pulls the voltage up to high
pinMode(SW1, INPUT_PULLUP)
Without PULLUP, an unpressed switch is left “floating”, i.e. it has an unknown potential (voltage)

16. Spartronics Experimenter Digital Pin Assignments13 12 11 10 9 8 7 6 5 4 3 2 1
SCK
MISO
MOSI SS
OC1
ICP
AIN1
AIN0 T1 T0
INT1
INT0
TXD
RXD
LED
pwm
LED0
LED1
LED2
LED3
red
green
blue
piezo
servo
SW0
SW1
SW2
SW3
Piezo rectangle is hyperlinked to an image of the actual Experimenter board. The piezo speaker is hyperlinked back to this slide.

17. Analog Signals Real world systems tend to be analog
Covers the range from 0V to 5V
Recall: Microcontrollers work in binary, so how does this work
We approximate!
Step-wise approximation of a continuous function

18. Analog Out (PWM) Concept
No facility exists on most microcontrollers to directly output an analog voltage (i.e., a voltage that varies continuously over the range of 0 to 5V)
Use Pulse Width Modulation (PWM) to approximate
Digital outputs are capable of 0V or 5V
Over a fraction (ton) of a time period tcycle, keep pin at 5V, the rest of the time, at 0V
Average voltage is proportional to ton/tcycle, called the ‘Duty Cycle’ 5V
time
So far, we’ve talked about digital I/O and analog input. How about getting an analog output?

19. Arduino analogWrite( )
analogWrite(pin, value);
0  value  255 (How many bits?)
0% duty cycle --> 0 V --> analogWrite(pin, 0);
100% duty cycle --> 5 V --> analogWrite(pin, 255);
Must be a PWM pin

20. Analog Output Example Fade the red LED in, then out
const byte ledPin = 3; // red RGB LED on Experimenter
const byte FADE_MAX = 255; // max value for setting duty cycle
const byte FADE_INC = 5; // increment for changing duty cycle
void setup() {
pinMode(ledPin, OUTPUT);
// note pinMode is not necessary for analog outputs }
void loop()
int fadeValue = 0; // PWM value
// fade in from min to max in increments of 5 points:
for(fadeValue = 0 ; fadeValue <= FADE_MAX; fadeValue +=FADE_INC)
analogWrite(ledPin, fadeValue); // sets the value (range from 0 to 255):
// fade out from max to min in increments of 5 points:
for(fadeValue = FADE_MAX; fadeValue >= 0; fadeValue -=FADE_INC)
Fade the red LED in, then out
duty cycle is incremented then decremented
256 steps
0% to 100%

21. Arduino analogRead( ) analogRead(pin);
Returns an integer 0 – 1024 (how many bits?)
0 V --> analogRead(pin) == 0
5 V --> analogWrite(pin) == 1024
Must be an Analog pin

22. Spartronics Experimenter Analog Pin Assignments7 6 5 4 3 2 1
photocell
POT
temp sensor
The rectangle around cells for pins 2, 1, 0 are hyperlinked to an image of the actual Experimenter board. Each respective element is hyperlinked back to this slide.

23. Resolution
All analog to digital and digital to analog systems have a minimum detectable change. This is the resolution of the system
On these Arduinos
8 BIT DAC (digital to analog conversion)
5V / 28 = 20 millivolts
10 BIT ADC (analog to digital conversion)
5V / 210 = 5 millivolts

24. Arduino map map(val, from_low, from_high, to_low, to_high);
y = map(x, 0, 256, 0, 1024);
Maps a value stored in x which has a range from 0 – 256 and spreads over the range from 0 – 1024 (i.e. 0 stays 0, 128 becomes 512, and 256 becomes 1024) and stores the new value in y

25. Serial console
Allows the microcontroller to provide text feedback to the programmer

26. Arduino Text Output No screen Serial output RS232 over USB
Console built into the Arduino IDE

27. Example: Serial Console
void setup() {
// initialize serial comm at 9600 bits per second:
Serial.begin(9600); }
// the loop routine runs over and over again forever:
void loop() {
Serial.println("Wax on");
delay(100);
Serial.println(“Whine at Mr. Miyagi");
Serial.println("Wax off");
// place at least a 1 millisecond delay for stability

28. Analog In with Serial Out
#define MAX_DELAY_TIME // max delay in ms
#define MIN_DELAY_TIME // min delay in ms
#define MAX_POT_VALUE // max pot reading
#define MIN_POT_VALUE // min pot reading
const byte POTPIN = 1; // pot output on pin 1
const byte LEDPIN = 6; // blue LED on pin 6
void setup() {
pinMode(LEDPIN, OUTPUT);
pinMode(POTPIN, INPUT); // documents use of potpin
Serial.begin(9600); // init serial comm at 9600 bps }
void loop() {
static unsigned int potVoltage = 0;// value of pot voltage
static unsigned int delay_ms = 0;
potVoltage = analogRead(POTPIN); // read pot
delay_ms = map(potVoltage, // convert pot value to delay
MIN_POT_VALUE,MAX_POT_VALUE,
MIN_DELAY_TIME,MAX_DELAY_TIME);
Serial.print("sensor = " ); // print to monitor
Serial.print(potVoltage);
Serial.print(" delay, ms = " );
Serial.println(delay_ms); // print delay and linefeed
digitalWrite(LEDPIN, HIGH); // turn the LED on
delay(delay_ms); // wait for delay_ms
digitalWrite(LEDPIN, LOW); // turn the LED off:
Read the POT
Note: analog voltage!
0 V  0
5 V  1023
Blink an LED at a rate proportional to the pot voltage
Output the pot voltage to the serial monitor
Initialize with Serial.begin()
Map voltage to delay
Write a line with Serial.print or Serial.println
So far, we’ve been dealing with digital I/O: just on or off. Now we want to work with a sensor that gives an output signal that can vary in a continuous (non-discrete) way over 0V to 5V.
The analog pins can be used as digital pins if desired.

29. This Week In Lab – Servo and Laser Module
Standard RC Servo
Diode Laser Module

30. RC Servo Construction Operation Wiring Black is ground Red is power
White/yellow is control
Arduino code
#include <servo.h>
Create a servo object
Attach the servo object to a pin
servo.write(position), where position is an integer between 0 and 180

31. #include <Servo.h> #define POT_PIN 1 #define SERVO 10 #define SERVO_DELAY 10 Servo myservo; //Create servo object to control servo void setup() { myservo.attach(SERVO); // Attaches servo object to pin 10 } void loop() static int pos = 0; // variable to store servo position for(pos = 0; pos < 180; ++pos) //goes from 0 to 180 degrees in 1 degree increments myservo.write(pos); //tell servo where to go delay(SERVO_DELAY); //delay to let servo move to position for(pos = 180; pos > 0; --pos) //returns to 0 from 180 in 1 degree increments myservo.write(pos); delay(SERVO_DELAY);
Servo_Knob.pde

32. References
Modular Programming in C
math.h
Arduino Home Page. (2017, September 21). Retrieved September 21, 2017, from