1. Lecture 9: Microcontrollers – part 1 BJ Furman 29OCT2012

2. The Plan for Today Microcontrollers for engineering applications  What is a microcontroller?  How are microcontrollers used?  The Arduino hardware platform  The Spartronics Experimenter board  Programming the Arduino Basic steps Digital I/O Analog I/O

3. Learning Objectives Explain what a microcontroller is Explain where microcontrollers are used Describe the Arduino prototyping platform Describe the Spartronics Experimenter board Explain what is meant by a pin being an input or an output Write programs for the Arduino that can do:  Digital I/O  Analog I/O

4. 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

5. Where are Microcontrollers Used? Everywhere!  Car  Phone  Toothbrush  Microwave oven  Copier  Television  PC keyboard  Appliances http://ecomodder.com/wiki/index.php/MPGuino

6. 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 $22 - $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/

7. The Spartronics Experimenter Board Momentary SPST push-button switches Red LEDs Piezo speaker Potentiometer (pot) Temperature sensor Light sensor Dual 7-segment display 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 Dual 7-segment display

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

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

10. 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 }

11. 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 …  ?

12. 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

13. 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

14. 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

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

16. 131211109876543210 SCKMISOMOSISSOC1ICPAIN1AIN0T1T0INT1INT0TXDRXD LED pwm LED0LED1LED2LED3 greenbluered piezo servo SW0SW1SW2SW3 Spartronics Experimenter Digital Pin Assignments

17. 76543210 photocellPOTtemp sensor Spartronics Experimenter Analog Pin Assignments

18. Code to Set Up Button Pins Two steps: 1. Make the pin an INPUT pinMode() 2. Turn the pull-up resistor on digitalWrite() a 1 to the pin const byte SW0 = 12; // button SW0 const byte SW1 = 8; // button SW1 const byte SW2 = 7; // button SW2 const byte SW3 = 4; // button SW3 void setup() { pinMode(SW0, INPUT); // make SW0 an INPUT digitalWrite(SW0, HIGH); // turn on pullup resistor etc. } (See full_test.pde for a more elegant approach to setting up button pins)

19. Digital I/O Example - Problem Statement Write a program to turn on the blue of the RGB LED (connected to digital pin 6) when SW0 is pressed (off otherwise) PPseudocode: define pin assignments configure pins (which are input, which are output) loop forever iif SW0 button is pressed mmake pin 6 high eelse mmake pin 6 low

20. Digital I/O Example - Pin Assignment and Configuration Refine the pseudocode:  define pin assignments const byte RGB_blue_pin = 6; const byte SW0_pin = 12;  configure pins (in function setup()) RGB_blue_pin  make it an _______ SW0_pin  make it an ______ turn on pull-up resistor on SW0 pin  pin will read high (1) until pulled low (0)  see schematic void setup() { pinMode(RGB_blue_pin, OUTPUT); pinMode(SW0_pin, INPUT); digitalWrite(SW0_pin, HIGH); } OUTPUT INPUT

21. Digital I/O Example - loop() Algorithm Refine the pseudocode, cont. :  loop forever (use function loop()) If button is not pressed:  voltage on button pin 12 will be _______  make pin 6 voltage low (LED will go off or stay off) If button is pressed:  voltage on button pin 12 will be _______  make pin 6 voltage high (LED will go on or stay on) void loop() { if(digitalRead(SW0_pin) == LOW) { digitalWrite(RGB_blue_pin, HIGH); } else { digitalWrite(RGB_blue_pin, LOW); } high (5V) low (0V)

22. Digital I/O Example - Arduino Program Arduino program Suppose a change to the specifications: LLED is on until button pressed, then off CContrast mechatronic approach vs. non- mechatronic re-wire, or… re-program the mechatronics approach separates the sensing elements from the control elements /* Blue_LED_button_cntrl1 - turns on blue LED when SW0 on Experimenter board is pressed, off otherwise */ /* pin assignments */ const byte RGB_blue_pin = 6; const byte SW0_pin = 12; /* configure pins */ void setup() { pinMode(RGB_blue_pin, OUTPUT); pinMode(SW0_pin, INPUT); digitalWrite(SW0_pin, HIGH); } /* loop forever */ void loop() { if(digitalRead(SW0_pin) == LOW) digitalWrite(RGB_blue_pin, HIGH); else digitalWrite(RGB_blue_pin, LOW); }

23. /* Blue_LED_button_cntrl1 - turns on blue LED when SW0 on Experimenter board is pressed, off otherwise */ /* pin assignments */ const byte RGB_blue_pin = 6; const byte SW0_pin = 12; /* configure pins */ void setup() { pinMode(RGB_blue_pin, OUTPUT); pinMode(SW0_pin, INPUT); digitalWrite(SW0_pin, HIGH); } /* loop forever */ void loop() { if(digitalRead(SW0_pin) == LOW) digitalWrite(RGB_blue_pin, HIGH); else digitalWrite(RGB_blue_pin, LOW); } Digital I/O Example - Modification Modify Arduino program, so that LED is on until button is pressed, then turns off HHow? Pin assignments? ssetup()? NNeed to turn on the LED! lloop()? SSwap values of second argument in digitalWrite calls

24. Comparison of Digital I/O Programs /* Blue_LED_button_cntrl1 - turns on blue LED when SW0 on Experimenter board is pressed, off otherwise */ /* pin assignments */ const byte RGB_blue_pin = 6; const byte SW0_pin = 12; /* configure pins */ void setup() { pinMode(RGB_blue_pin, OUTPUT); pinMode(SW0_pin, INPUT); digitalWrite(SW0_pin, HIGH); } /* loop forever */ void loop() { if(digitalRead(SW0_pin) == LOW) digitalWrite(RGB_blue_pin, HIGH); else digitalWrite(RGB_blue_pin, LOW); } /* Blue_LED_button_cntrl2 - turns off blue LED when SW0 on Experimenter board is pressed, on otherwise */ /* pin assignments */ const byte RGB_blue_pin = 6; const byte SW0_pin = 12; /* configure pins */ void setup() { pinMode(RGB_blue_pin, OUTPUT); pinMode(SW0_pin, INPUT); digitalWrite(SW0_pin, HIGH); digitalWrite(RGB_blue_pin, HIGH); } /* loop forever */ void loop() { if(digitalRead(SW0_pin) == LOW) digitalWrite(RGB_blue_pin, LOW); else digitalWrite(RGB_blue_pin, HIGH); }

25. Analog In with Serial Out Read the POT N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 #define MAX_DELAY_TIME 1000 // max delay in ms #define MIN_DELAY_TIME 10 // min delay in ms #define MAX_POT_VALUE 855 // max pot reading #define MIN_POT_VALUE 0 // min pot reading const byte potPin = 1; // pot output on pin 1 const byte ledPin = 6; // blue LED on pin 6 unsigned int potVoltage = 0; // value of pot voltage unsigned int delay_ms; void setup() { pinMode(ledPin, OUTPUT); pinMode(potPin, INPUT); Serial.begin(9600); // init serial comm at 9600 bps } void loop() { potVoltage = analogRead(potPin); // read pot delay_ms = map(potVoltage,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: delay(delay_ms); // wait for delay_ms } POT_input_Serial_Out.pde

26. Effect of Using delay() Leads to poor (slow) performance as delay time increases Try to avoid long delays  Use millis() instead  Check for time exceeding millis() + delay_time  Ex. POT_in_Serial_Out.pde Note also the use of #ifdef for ‘conditional compilation’ Note how roll-over of millis() is handled

27. 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) UUse Pulse Width Modulation (PWM) to approximate an analog voltage Digital outputs are capable of 0V or 5V Over a fraction (t on ) of a time period t cycle, keep pin at 5V, the rest of the time, at 0V TThe average voltage is proportional to t on /t cycle, which is called the ‘Duty Cycle’ SSee Lab View PWM_demo.vi 5V time

28. 30% duty cycle Front Panel Block Diagram

29. Arduino analogWrite( ) analogWrite (pin, value);  0  value  255 0% duty cycle --> 0 V --> analogWrite (pin, 0); 100% duty cycle --> 5 V --> analogWrite (pin, 255); fade_example.pde (see next page)

30. Analog Output Example Fade the red LED in, then out  duty cycle is incremented then decremented  256 steps 0% to 100% 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); } void loop() { int fadeValue; // 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) { analogWrite(ledPin, fadeValue); // sets the value (range from 0 to 255): } fade_example.pde

31. Review

32. 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/

33. Spartronics Experimenter Board