EGG 101L INTRODUCTION TO ENGINEERING EXPERIENCE

Transcription

1 EGG 101L INTRODUCTION TO ENGINEERING EXPERIENCE LABORATORY 2: INTRODUCTION TO ARDUINO UNO AND DANGER SHIELD DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING UNIVERSITY OF NEVADA, LAS VEGAS GOAL: This section introduces the basic hardware involved in the experiments and activities performed in these laboratory exercises. Namely the Arduino UNO and Danger Shield. OBJECTIVES: Familiarize the user with the Arduino UNO Familiarize the user with the Danger Shield OVERVIEW AND REQUIREMENTS: Arduino Development Platform Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It's intended for artists, designers, hobbyists, and anyone interested in creating interactive objects or environments. [ At its core, the Arduino development platform is a microcontroller placed in a development shell with all the necessary components to make it easy to use. Arduino s flagship platform is the Arduino Uno, a microcontroller board based on the Atmega328. It has 14 digital input/output pins, 6 analog inputs, a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button. It is all encompassing in terms of supporting and using the microcontroller. It can be powered via an AC adapter or connected to a computer via USB, which is also used for programming. DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING 1

2 Microcontrollers Microcontrollers are small integrated circuits that are used in a wide variety of day to day household products and applications. They consist of a processor, memory, and programmable inputs/output peripherals to control. You can think of it as a small computer on a single integrated circuit, typically designed for embedded applications. Microcontrollers are designed to execute specific tasks to control a system, such as taking input from a remote control to change the channel on a television. Microcontrollers have become quite common in many products such as appliances, computer equipment, automobiles, and extending as far as industrial robotics. They are designed to be self sufficient and cost effective, giving them a use in a large variety of specific tasks. If you can think of any digital interface used in many household appliances or technological devices you can very safely assume that a microcontroller is involved in the control of the interface. Power The Arduino Uno can be powered via the USB connection or with an external power supply. The power source is selected automatically. External (non-usb) power can come either from an AC-to-DC adapter (wall-wart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack. Leads from a battery can be inserted in the Gnd and Vin pin headers of the POWER connector. The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts. The power pins are as follows: VIN: The input voltage to the Arduino board when it's using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin. 5V: This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7-12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it. 3V3: A 3.3 volt supply generated by the on-board regulator. Maximum current draw is 50 ma (milliamps). GND: Ground pins. DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING 2

3 Memory The ATmega328 has 32 KB (with 0.5 KB used for the bootloader). It also has 2 KB of SRAM and 1 KB of EEPROM (which can be read and written with the EEPROM library). Input and Output Each of the 14 digital pins on the Uno can be used as an input or output. They operate at 5 volts. Each pin can provide or receive a maximum of 40 ma and has an internal pull-up resistor (disconnected by default) of kohms. Serial: 0 (RX) and 1 (TX). Used to receive (RX) and transmit (TX) TTL serial data. These pins are connected to the corresponding pins of the ATmega8U2 USB-to-TTL Serial chip. External Interrupts: 2 and 3. These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value. See the attachinterrupt() function for details. PWM: 3, 5, 6, 9, 10, and 11. Provide 8-bit PWM output with the analogwrite() function. SPI: 10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK). These pins support SPI communication using the SPI library. LED: 13. There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it's off. The Uno has 6 analog inputs, labeled A0 through A5, each of which provide 10 bits of resolution (i.e different values). By default they measure from ground to 5 volts, though is it possible to change the upper end of their range using the AREF pin and the analogreference() function. Additionally, some pins have specialized functionality: TWI: A4 or SDA pin and A5 or SCL pin. Support TWI communication using the Wire library. AREF. Reference voltage for the analog inputs. Used with analogreference(). Reset. Bring this line LOW to reset the microcontroller. Typically used to add a reset button to shields which block the one on the board. [ DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING 3

4 Danger Shield The Danger Shield is a top mounted Arduino UNO shield that equips a large variety of inputs and outputs to the Arduino without the use of any kind of breadboard. Each input/output is connected to the Arduino s digital and analog pins. Analog pins 0 to 2 connects to 3 individual 10k ohm linear slide potentiometers output an analog value between 0 and Analog pin 3 is connected to a photocell. This device chances resistance depending on the amount of light it is exposed to. Analog pin 4 is connected to a temperature sensor which sends out an analog value representative of the current ambient temperature. Digital pins 2 and 9 are connected to a capacitve touchpad, which is able to sense touch when pressure is applied to the area. Digital pin 3 is connected to a small 12mm round buzzer that operates in the 2kHz range. It can be used to generate various sounds and even create simple music. Digital pins 5 and 6 are connected to LED s in series with a 330 ohm resistor. For these labs the LED s will be red and green respectively. Digital pins 4, 7, and 8 are connected to the 8-bit shift register, which is used to drive the 7 segment display. Digital pins 10 to 12 are connected to momentary push buttons that send the signal low when buttons are pressed (low active). The following exercises will display the use and function of the potentiometers and the capactive sensor. COMPONENTS: Components: Arduino Uno USB A-B Cable Danger Shield Host PC Installed Arduino Uno drivers and IDE Provided Capacitive Sensor Library. DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING 4

5 PROCEDURES AND INFORMATION: Slider Potentiometers Attach the Danger Shield to the Arduino, making sure to properly align the pins. If you are using an R3 revision of the Arduino UNO, there will be 2 pins on each side that will have no corresponding pins on the shield. 1. Attach the Arduino UNO to the host PC with the use of the USB cable. Verify that the drivers have been properly installed. 2. Open the Arduino IDE and create a new sketch titled Sliders. Verify that the correct COM port is in use. DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING 5

6 3. Using the previous lab as a guide, verify and upload the following sketch to your Arduino UNO: // Global variables int val = 0; // Pin definitions #define SLIDER1 0 #define SLIDER2 1 #define SLIDER3 2 void setup() { Serial.begin(9600); //Start Serial Communication Serial.println("Danger Shield Potentiometer Test"); } void loop() { Serial.print("Sliders: "); val = analogread(slider1); Serial.print(" "); Serial.print(val); val = analogread(slider2); Serial.print(" "); Serial.print(val); val = analogread(slider3); Serial.print(" "); Serial.println(val); delay(300); } Fig. 1. Code 1. Verify your results by sliding all 3 potentiometers. The value range should be between 0 and Capacitive Sensor Download and extract the CapSense.zip file included in this lab. Copy the extracted CapSense folder into the arduino libraries folder Attach the Danger Shield to the Arduino, making sure to properly align the pins. If you are using an R3 revision of the Arduino UNO, there will be 2 pins on each side that will have no corresponding pins on the shield. Attach the Arduino UNO to the host PC with the use of the USB cable. Verify that the drivers have been properly installed. DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING 6

7 Open the Arduino IDE and create a new sketch titled CapSense. Verify that the correct COM port is in use. Using the previous lab as a guide, verity and upload the following sketch to your Arduino UNO: #include <CapSense.h> //Include the Cap Sense Library into our program // Global variables int val = 0; CapSense cs_9_2 = CapSense(9,2); //Initializes CapSense pins void setup() { Serial.begin(9600); //Start Serial Communication cs_9_2.set_cs_autocal_millis(0xffffffff); // Calibrates CapSense pin timing Serial.println("Danger Shield Cap Sense Test"); } void loop() { long start = millis(); long total1 = cs_9_2.capsense(30); Serial.println(total1); delay(10); } Fig. 2. Code 2. Verify your results by pressing your thumb against the capacitive sensor. The value reading should increase based on the pressure placed on the surface. DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING 7

8 DEMO AND SCREENSHOTS: Pushbutton Control: DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING 8

9 PRELAB: 1. List 2 different ways of installing a library. 2. Are the values from the sliders on Danger Shield analog or digital? What is the range of these values? EXPERIMENTS: Experiment 1 3. Run Code 1. Verify the operation of the Slider control, demonstrate the operation to the TA. 4. Modify the code: a. Add delay of 10 before each output to the serial monitor. b. Display slider values in separate lines: SLIDER1: val1 SLIDER2: val2 SLIDER3: val3 c. Demonstrate the operation to the TA Experiment 2 1. Run Code 2. Verify its operation, demonstrate to the TA. 2. Display: Value from cap sensor is: valuefromcap (where valuefromcap is the value that you read from capacitive sensor. 3. Demonstrate the operation to the TA Experiment 3 1. Display the following value in the serial monitor: Value of cap sensor C Increased by value from slider1 Decreased by ¼ of value from slider3 Therefore: Value = C + slider1 ¼ slider3 2. Demonstrate the operation to the TA POSTLAB REPORT DELIVERIES Include the following elements in your postlab report: 1. Theory of operation a. Describe what the pushbutton is. List 3 practical applications. b. Describe what the Capacitive sensor is. List 3 practical applications. 2. Results of the experiments For each experiment, include: a. The code that you developed for the experiment. The lines that were added must be commented with the explanation of what is their meaning. b. Brief explanation how the goal of the experiment was reached (e.g. in experiment 3, how the value was calculated) DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING 9

10 c. Screenshots of the serial monitor with the values, presenting the operation of your code 3. Answer the questions a. What optimal voltage range that should be supplied to the Arduino board? b. Is the value from cap sensor analog or digital? c. How many digital pins does the Arduino have? What voltage and current do they supply? d. How many analog pins are there? Define the SDA and SCL pins. 4. Conclusions a. Write down your conclusions, things learned, problems encountered during the lab and how they were solved, etc. DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING 10