CPSC 226 Lab Four Spring 2018

Transcription

1 CPSC 226 Lab Four Spring 2018 Directions. This lab is a quick introduction to programming your Arduino to do some basic internal operations and arithmetic, perform character IO, read analog voltages, drive a piezo buzzer. This is just the first step toward having your Arduino do more ambitious stuff like control servo motors, drive LCD and RGBW displays, respond to a TV remote control, maintain a real time clock, etc. This lab counts 20 points toward your final grade. Programming Arduino: You should design and write your Arduino code in a consistent style and include useful comments for the reader. This will make reuse of your code easier for you as well and you will not have to go back and re-invent things. One time obligatory reminder for all programmers: MAKE TWO (OR MORE) BACKUPS OF YOUR CODE! YOU DO NOT WANT TO SPEND HOURS ON CODING ONLY TO HAVE IT ALL DISAPPEAR WHEN YOU DO SOMETHING CARELESS AT 2:30 AM! I will not repeat this suggestion again. Prelab You should check out the website, our Electronics Cookbook text by Simon Monk, and the very helpful reference Arduino Cookbook, 2 nd edition by Michael Margolis, so you get a sense of what is available for sensors, motors, visual displays, etc. Useful online sources include the following: IMPORTANT: READ THROUGH THE API! As you know by now, each Arduino-compatible board (including those from Adafruit, Sparkfun, etc) supports different peripherals, sensors, etc which are often made accessible via an API implemented by a C++ library appropriate for that device and usually sample code along with it. Free libraries support real time clocks, SD cards, NeoPixels, motor drivers, etc. Your particular Arduino may have no sensors included or may have many sensors already on the board, such as the Esplora. Note the Arduino Esplora form factor does NOT allow use of standard Arduino shields nor does it have a standard barrel power receptacle for using a wall wart or battery power supply! This just means you will need to provide circuits for these devices off the Arduino boards. All these kinds of options will influence how you design your Arduino-based projects as we proceed. More on this is coming as we get deeper into design and Arduino coding. Read through the basic language constructs of Arduino in the recipes in Chapter 10.1, 10.2 in your textbook. You do not need to know all the details of the language yet but it is very useful to know what C++ and Java equivalents exist in Arduino. Variables, loops, if...else, math operations, programmer defined functions, parameters, etc are all very much like Java but often simpler in Arduino. These are what this lab is about so you get used to using a variety of Arduino API functions, methods, and interfacing hardware. I strongly suggest thumbing through Electronics Cookbook just to see what kinds of hardware can be interfaced with Arduino (or Raspberry Pi). Next, look through recipes Chapters 1-8 in Arduino Cookbook so you know where to locate code when you need to display serial output, read switches and analog inputs, connect to and control servos, display data on typical LCDs, read Sharp sensors, etc. A final word of caution. We are now entering the domain where you have to pay close attention to what you are actually doing when using LEDs, servos, sensors, and other devices. Misuse or improper connections can result in real damage to your Arduino, the servos and sensors, or both. I will be demonstrating connections

2 of devices to various models of Arduino. Download and install the latest version of the Arduino software at Software on your own computer. There are versions for all the major platforms. READ THE GET- TING STARTED DOCUMENTATION ABOUT ISSUES FOR EACH PLATFORM. GETTING THE USB DRIVER CONNECTION RIGHT IS OFTEN AN ANNOYING CHALLENGE. After installation, start up Arduino and check out the IDE environment available for programming Arduino devices. You will see your Arduino Editing/Compiling/Upload/Serial IO environment which looks something like Figure 1. Notice under the Arduino menu you can set basic preferences for your editing environment including font, line numbering, etc. The File menu allows open/edit/save source code files (Arduino originally called them sketches). Check out the MANY examples of Arduino sketches for doing all sorts of things. Note: You can verify (syntax check) any sketch but cannot upload a program to an Arduino board unless one is attached via USB cable, which we will do in the lab itself. For a similar reason, you cannot display messages in the IDE Serial Monitor until you have an Arduino connected by a USB cable. I will illustrate these processes in class. Looking at the form of the Arduino programming language you will notice it has very similar syntax to Java but more closely resembles C++, both Figure 1: Arduino IDE. OOP descendants of the venerable C programming language. You can program Arduino in C but that topic is beyond the scope of this course. We have other ambitions. At the Arduino IDE, open the File/Examples/Basics/Blink program. Notice the Blink program structure contains two methods/functions/subroutines: setup and loop. These two methods are required in all Arduino programs. The function setup is automatically called exactly once each time your Arduino program is executed or Arduino is reset. The function loop is automatically called endlessly whenever your program runs so you can use its automatic looping nature to read some data, compute a response, display results of the response, etc. This is not unlike the Processing language setup and draw functions. In fact, these two programming languages, Arduino and Processing, share a common heritage. Reading the comments in the Blink program, see if you can figure out how it would endlessly blink an LED on the Arduino board by executing the instructions given. What circuit must also be present on the board to safely blink an LED? Hint: there has to be at least an LED! Draw a schematic of just the LED/resistor arrangement you would expect to find when looking at an Arduino board schematic and go look at your Arduino UNO (or other board) schematic and find the circuit in question. A Quick Look at Hardware Look at your Arduino board (Duemilanove, UNO, MEGA, Boarduino, Metro, whatever...) and locate the digital pins labelled 0-13, the analog to digital (ADC) pins 0-5, +5V pin, external power connector, and GND pins on the edges of the board. Pins 0 and 1 are not usually available for our use as they are part of Arduino s USB/RX/TX communication channel. More on that in the coming days. We will exercise these digital and analog to digital pins in this lab. End of Prelab Start the Arduino IDE, wait a few seconds, then then under the Tools menu, select your Arduino board AND the proper serial port as I demonstrated in class. If no suitable USB board appears, re-read the Getting Started guide on the Arduino website for your particular Arduino board and the USB connection procedure. You might need to install USB drivers for Windows when using Arduino.

3 NOTE: If you are using a third party board such as Adafruit Metro, you should add that new board to the Arduino IDE so it will appear as a board option! Instructions are found at Open the File/Examples/Basics/Blink example. Verify (this means syntax check/compile) and then upload the program to your Arduino so you know the board works and the communication channel is established. You should see an LED on the board blinking. Exercise 1. Modify the Blink program so the LED blinks faster. Once this works correctly, modify your sketch so the LED blinks slower. Modify the Blink program so the LED blink rate changes from slower to faster then back to slower and so on. You can declare and use an integer variable to set variable delays. Now, save your program and include your program code in your lab writeup. Note, you cannot save a sketch to replace the Arduino Examples provided by the IDE. SAVING A SKETCH REQUIRES PUTTING IT INSIDE AN IDENTICALLY NAMED FOLDER. Annoying, yes, but there it is. Below is about the simplest program to provide symbolic program feedback from Arduino to the user/programmer. Notice we have to initialize our Serial object using Serial.begin(...) in function setup and then use the Serial.println(...) method to write to the Serial Monitor window. You open the Serial Monitor using the icon at the upper right of the Arduino IDE. void setup() { // put your setup code here, to run once: Serial.begin(9600); // Sets baud rate for serial communication } void loop() { // put your main code here, to run repeatedly: Serial.println("Hello World"); delay(1000); } Exercise 2. Write, save, compile and run this program (call it HelloWorld) so it works as expected. Experiment with Serial.print(...) instead of Serial.println(...) so you get comfortable with printing to the Serial Monitor. Change the baud rates of the Serial object AND the Serial Monitor. What happens if their baud rates do not match? Add some integer, char, boolean, byte, etc variables then modify your Hello World example so it prints integer values instead of just fixed character strings. Note: You can control printing format of various data types by using the optional second parameter like these examples show below. Try out a few examples so you see how to control the format of printed numbers. Serial.println(28, DEC); Serial.println(28, HEX); Serial.println(28, BIN); Serial.println(0x35, DEC); // 0x prefix designates hexadecimal (base 16) value Serial.println(0x35, HEX);

4 Serial.println(0x35, BIN); Serial.println(0b , DEC); // 0b prefix designates binary (base 2) value Serial.println(28,OCT); Exercise 3. What is the largest positive integer which can be held in an Arduino int type variable? What value do you get if you add one to that value? Show me code that helped you figure this out. Check out the File/Examples/Communication/ASCIITable sketch. Compile, run it, and see if you understand how the program does what it does. After the ASCII table is printed, press the reset button on the Arduino board, what happens? Exercise 4. Modify the ASCIITable sketch so it prints all the ASCII chars from What is the result of extending the print range? What was printed? Can you guess from the output what some of the low (0-31) ASCII chars do? Exercise 5. Open the File/Examples/Basic/BareMinimum sketch. Add an integer variable to this code, save it as CountingNumbers, and now add code to have your program print the sequence 1, 2, 3,..., 100 then enter an infinite loop and print nothing more. Include your program code in your lab writeup. Exercise 6. Modify your previous code so you print this endless sequence 2, 3, 5, 7, 11, 13, 17,... You MUST create a function in your code which returns a boolean type to determine whether an integer is prime or not as part of your code. Save this new program as Primes and include this primo program code in your lab writeup. Exercise 7. Design, write, run and debug a single program called AllTypesOfStuff to demonstrate that Arduino supports boolean, float, char, int, unsigned int, byte, double, and array data types pretty much unchanged from your familiar Java syntax. Include your program code in your lab writeup. Exercise 8. Read the API for String types in Arduino. Design and create an Arduino program, not a copy of an existing Example, which illustrates how to declare a String object and use at least five familiar string functions such as computing length, get a char at a position in a String object, etc. Extra Credit: Design and write an Arduino program to code/decode the so-called Caesar cipher method of encoding text messages. If you type an coded message in the Serial Monitor, Arduino should decode it and display the clear text. If you send clear text, Arduino should show the encoded message. Return to hardware. Basic Arduinos have six analog to digital converter (ADC) pins labeled A0-A5 which allow us to read analog voltages from 0V to +5V as binary coded values. This is very useful in handling interactions with an analog world of sensor voltages, light intensity values, sound levels, etc. BE SURE YOU UNDERSTAND THE PLACEMENT AND LIMITATIONS OF +5V AND GND PIN LOCATIONS ON ARDUINO. IMPROPERLY SHORTING +5V TO GND PINS ON ARDUINO CAN DESTROY THE VOLTAGE REG- ULATOR WHICH MAKES THE BOARD UNUSABLE! ASK IF YOU ARE UNSURE! Figure 2: Potentiometer symbols. Recall the schematic in Figure 2 shows a potentiometer which is ideal for making an adjustable voltage divider. Remember the value of a pot is the total resistance between the two outer pins 1 and 3. If we apply V+/Vdd/Vcc to pin 1 and GND to pin 3, the middle pin 2, or wiper, acts as output of an adjustable voltage divider.

5 Exercise 9. Create a circuit like this one shown in Figure 3 on a breadboard using a potentiometer of at least 10K ohms and some jumper wires. Notice the pot has +5V connected to one end and GND connected to the other. The center wiper is the output of a voltage divider. Check the output using a yellow/orange DVM to see it works as you think it will. Exercise 10. Read the Arduino sketch found at File/Examples/Basics/AnalogReadSerial and see how you can measure and print the analog voltage value at the pot slider pin. Now code your own program that simply reads the analog pin A3 and prints a resulting integer value to the Serial Monitor. Record some output ADC values. From the values you obtain, can you determine the numeric range of the analog to digital converter on Arduino? Include your code in the writeup. Figure 3: Potentiometer voltage divider. Exercise 11. Now read the Arduino sketch found at File/Examples/Analog/AnalogOutSerial. What does this code do? How does it differ from the previous analog reading sketch? What new Arduino syntax/constructs/functions does it contain? Notice this analog read then set PWM (look it up!) presumes you have an LED (with current limiting resistor we presume) connected to Arduino (digital pin) D9. So, make and add that LED circuit and test the code to see what it does. Include your schematic and describe how the program works. Use a DVM to measure voltage at the output pin D9. What do you read? Exercise 12. Design a simple sensor circuit that allows Arduino to detect light levels using a Cadmium Sulfide (CdS) photocell, a resistor of a suitable value, a flashlight/phone, and an Arduino. A circuit similar to this was covered in Lab 2. Remember, double check your circuit so you avoid high current flow through direct shorts or very low resistance. Here is the action we want. Light falls on your CdS sensor which affects the voltage divider output feeding an Arduino ADC. The program prints a notice to the Serial Monitor whenever the analog level indicates the light beam has been disrupted. This makes is a break beam sensor and is the essential circuit used in car washes, parking garage sensors, security systems, etc. Arduino speaks up! We want to make Arduino beep to signal when your light sensor has been triggered. You should look for a tutorial/recipe on Arduino and piezo buzzers before you begin to design your circuit and code. Include a very tidy schematic of your entire circuit, including Arduino, sensor and buzzer, as well as the source code you used for your detector. End of lab

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