1. Lecture 7: Microcontrollers & I/O Bryan Burlingame 14 October 2015

2. Smart, connected products require a rethinking of design. At the most basic level, product development shifts from largely mechanical engineering to a true interdisciplinary systems engineering. Porter, M., & Happelmann, J. (2015, October). How Smart, Connected Products Are Transforming Companies. Harvard Business Review, 96- 112, 114.

3. Announcements Exam in two weeks  This is the final lecture which will be on the exam Homework #3 due up front Homework #4 (exam review) posted  Due with the mid-term Read Ch. 3 -4 in text Open lab Wednesday evenings, 5:15  Eng 213 Arduino lab kits available from Eric Wertz

4. The Plan for Today How can I interact with the user  Obtaining input from the keyboard  Brief decisions Microcontrollers for engineering applications  What is a microcontroller?  How are microcontrollers used?  The Arduino hardware platform  The Spartronics Experimenter board  Programming the Arduino

5. 5 scanf() function (just a brief treatment!) scanf() is like the reverse of printf  It reads data entered via the keyboard  Similarities to printf(): Needs a format string first Many common format specifiers, which indicate the type of data expected from the keyboard  Which must match the data arguments Any number of data arguments  Differences from printf(): Data argument identifiers must be preceded with an ampersand (&)  The & ahead of the variable signifies the address in memory where the data will be stored (its a pointer to the variable)  Beware!!! Forgetting the & is a common error.  More on the & later this semester

6. 6 scanf() function, cont.  Differences from printf(), cont.: Characters other than a conversion string, a space, a newline character, or a vertical tab must match characters in the input stream A space, horizontal tab, or newline character in the format string causes scanf() to skip over leading white space up to the next nonspace character scanf(“Distance= %lf", &num1);  Will skip leading spaces before the value num1  Must find a match to the string literal, Distance= (or else it will stop reading the input and will return the number of successful conversions that were stored (try entering a space before typing Distance=) Darnell & Margolis (1996)

7. 7 scanf example Prompt the user for two floating point numbers, and store them in floating point variables of type double named x and y #include int main( void ) { float x = 0; float y = 0; char buffer[BUFF_SIZE]; printf( "Enter two floats (x y): "); scanf( "%f %f", &x, &y ); printf( “You entered %f and %f\n”, x, y ); return 0; }

8. More robust input We use two commands to properly obtain input from the keyboard fgets & sscanf fgets places data collected form the keyboard into a buffer stored as a character string up to a carriage return (when the user presses return or enter) fgets( buffer, sizeof(buffer), stdin );

9. Formatted Input (2) sscanf is from the *scanf family  We’ll use fscanf later in the semester sscanf splits the input into variables Uses conversion metasymbols like scanf sscanf( buffer, “%d %f”, &x, &y); Avoids many (though not all) weaknesses in scanf  Realistically, don’t use scanf… well ever

10. Formatted Input (3) #include #define BUFF_SIZE 100 //note symbolic const int main( void ) { float x = 0; float y = 0; char buffer[BUFF_SIZE]; printf( "Enter two floats (x y): "); fgets( buffer, sizeof(buffer), stdin ); sscanf( buffer, "%f %f", &x, &y ); printf( “You entered %f and %f\n”, x, y ); return 0; }

11. Flow control These Boolean operations are used along with flow control (or branching) statements to control the flow of a program Decisions TrueFalse

12. Simple if - example int speed = 5; if( speed > 65 ) { // do everything until the closing } printf( “You are speeding!\n” ); } // technically, when one statement is between // the curly braces, the braces are optional. // Even so, don’t omit them else { // note the indentation. printf( “You are not speeding\n” ); }

13. What is a Microcontroller? A small computer usually implemented on a single IC that contains a central processing unit (CPU), some memory, and peripheral devices such as counter/timers, analog-to- digital converters, serial communication hardware, etc. http://www.amazon.com/AVR-Pin-20MHz- 32K-ATMega328/dp/B004G5AVS6 ATmega328 the ‘brain’ of the Arduino

14. Where are Microcontrollers Used? Everywhere!  Car (50 – 70 per car! (EDT Design News, July 2009))  Phone  Toothbrush  Microwave oven  Copier  Television  PC keyboard  Appliances

15. The Arduino Platform Atmel ATmega328 microcontroller 14 digital I/O pins  6 with PWM 6 analog I/O pins 32 kB (-2 kB) Flash memory 2 kB RAM 1 kB EEPROM 16 MHz clock $10 - $30 built  $13 ‘breadboardable’ FTDI USB chip Digital Pins Analog Pins USB jack Microcontroller power jack Voltage regulator Pwr/GND Pins ICSP Header Reset Button Power LED Pin 13 LED Rx + Tx LEDs http://arduino.cc/

16. The Spartronics Experimenter Board Momentary SPST push-button switches Red LEDs Piezo speaker Potentiometer (pot) Temperature sensor Light sensor RGB LED http://www.sparkfun.com/commerce/images/products/00105-03-L_i_ma.jpg Cathode R G B speaker Pot RGB LED Light sensor

17. Handling the Arduino - How NOT to Do It! Improper Handling - NEVER!!!

18. Handling the Arduino - The Proper Way Proper Handling - by the edges!!!

19. Recall: Fundamental Flow of a C Program Start Main End Return value to Operating System (very important!) Calling parameters Available from Operating System

20. Fundamental Flow of an Arduino Program Start Setup Loop End

21. Programming the Arduino An arduino program == ‘sketch’  Must have: setup() loop()  setup() configures pin modes and registers  loop() runs the main body of the program forever  like while(1) {…}  Where is main() ? Arduino simplifies things Does things for you /* Blink - turns on an LED for DELAY_ON msec, then off for DELAY_OFF msec, and repeats */ const byte ledPin = 13; // LED on digital pin 13 const int DELAY_ON = 1000; const int DELAY_OFF = 1000; // setup() method runs once, when the sketch starts void setup() { // initialize the digital pin as an output: pinMode(ledPin, OUTPUT); } // loop() method runs forever, // as long as the Arduino has power void loop() { digitalWrite(ledPin, HIGH); // set the LED on delay(DELAY_ON); // wait for DELAY_ON msec digitalWrite(ledPin, LOW); // set the LED off delay(DELAY_OFF); // wait for DELAY_OFF msec }

22. Using setup() A digital pin can either be an output or an input  Output your program determines what the voltage on a pin is (either 0V (LOW or logic 0) or 5V (HIGH or logic 1)  Information is sent out  Input the world outside the microcontroller determines the voltage applied to the pin  Information is taken in const byte ledPin = 13; // LED on digital pin 13 void setup() { // initialize the digital pin as an output: pinMode(ledPin, OUTPUT); } where can you find out about the commands, etc? http://arduino.cc/en/Reference/Extended pinMode()  sets whether a pin is an input or an output ledPin  byte constant assigned the value of 13 OUTPUT is a macro defined constant Which has the value 1 INPUT is a macro …  ?

23. Blinking the LED in loop() digitalWrite()  Causes the voltage on the indicated pin to go HIGH (+5V) or LOW (0V)  Note: must first configure the pin to be an output To make pin go to 5V (high):  digitalWrite(pin_num,HIGH);  Best to #define pin num. To make pin go to 0V (low):  digitalWrite(pin_num,LOW); delay()  Causes the program to wait for a specified time in milliseconds #define LED_PIN 13 // LED on digital pin 13 #define DELAY_ON 500 // in ms #define DELAY_OFF 100 void setup() { // initialize the digital pin as an output: pinMode(LED_PIN, OUTPUT); } void loop() { digitalWrite(LED_PIN, HIGH); // turn LED on delay(DELAY_ON); // wait for DELAY_ON ms digitalWrite(LED_PIN, LOW); // turn LED off delay(DELAY_OFF); // wait for DELAY_OFF ms } http://arduino.cc/en/Reference/Extended

24. Spartronics Experimenter LED Pinout Pin and LED map  11 - LED0 (red) or RGB (red)  9 - LED1 (red) or RGB (green)  6 - LED2 (red) or RGB (blue)  3 - LED3 (red)  13 - LED on Arduino Jumper determines whether pins map to red LEDs or the RGB 11963

25. 131211109876543210 SCKMISOMOSISSOC1ICPAIN1AIN0T1T0INT1INT0TXDRXD LED Pwmpwm LED0LED1LED2LED3 RedGreenBlue (v1 red) Piezo servo SW0SW1SW2 speaker SW3 Spartronics Experimenter Digital Pin Assignments

26. 12874 Spartronics Experimenter Button Pinout Pin and Button map  12 - SW0  8 - SW1  7 - SW2  4 - SW3 How should the associated pins be configured: as INPUTS or as OUTPUTS?  ‘Active LOW’ Voltage on pin changes from 5V to 0V when switch is pressed Need to turn on internal ‘pull-up’ resistor, so that 5V is supplied to pin To ATmega328

27. Pull-up Resistor Concept ATmega328 PD3 V TG = +5V 0 1 ATmega328 PD3 V TG = +5V 0 1 Pull-up resistor OFFPull-up resistor ON Pull-up resistor

28. Simple if – example (Arduino) #define BUTTONPIN 12 #define LEDPIN 3 int buttonState = 0; void setup() { pinMode( LEDPIN, OUTPUT ); pinMode( BUTTONPIN, INPUT_PULLUP ); } void loop() { int buttonState = digitalRead( BUTTONPIN ); if( buttonState == LOW ) //note double == for equivalence { //If the button is pressed, turn on the LED digitalWrite( LEDPIN, HIGH); } else { // otherwise, turn it off digitalWrite( LEDPIN, LOW); }

29. References Microcontroller. (2009, November 20). In Wikipedia, the free encyclopedia. Retrieved November 21, 2009, from http://en.wikipedia.org/wiki/Microcontroller http://en.wikipedia.org/wiki/Microcontroller Arduino Home Page. (2009, November 21). Retrieved November 21, 2009, from http://arduino.cc/ http://arduino.cc/