To lead your students through this activity, you will need your computer, attached to a projector, for projecting your code for students to see.

Transcription

1 To lead your students through this activity, you will need your computer, attached to a projector, for projecting your code for students to see. STEP 1: PREPARE TO PROGRAM 1. Launch the IDE by clicking on the Arduino icon in the start menu. 2. Select the hardware. Click Tools, then Board, and be sure Arduino Uno is selected. Requests to reproduce any part of this material may be made to Engineer Your World. Page 1 of 8

2 3. Select the port. Next choose the correct communications (COM) port for the computer to use. If you only have one thing plugged into your computer, then usually there is only one COM port shown, and you can select it with the drop-down menu. Click Tools, and Serial Port. Select the correct port (it will likely default to the correct port). If you have multiple ports, you can unplug the microcontroller and see which ports go away. Then plug it back in and see if the port comes back. This is the correct port. 4. Change the font size (optional). If it will help your students to see your generated code more clearly, you may choose to increase the font size. To do this, click on File, then Preferences: Requests to reproduce any part of this material may be made to Engineer Your World. Page 2 of 8

3 You will see a popup box; enter a font size of 16 or 18 in the appropriate box (the default is 12). Click OK. Note that it is possible you may need to close and re-open the Arduino IDE in order for this change to take effect. STEP 2: SETTING PROPER INPUT/OUTPUT DESIGNATIONS TO THE ARDUINO PINS 1. Add comments at the header to represent the new task: Global Variables Up until now, we have placed variables in the void setup()portion of our code, since this was the place the variables were used. For this activity, we will have the same variables used in both the void setup() and void loop() parts of our program. We cannot declare variables in the setup part because it won t be recognized by the loop part, and vice-versa. To work around that, we have to use global variables. These variables are introduced before the void setup()and void loop() parts, and they are recognized by the entire program. We must make sure the following lines of code come before the void setup()portion of our code. Also include appropriate comments. int speakerpin = 12; int buttonpin = 3; Now, begin with the void setup()part and create the skeleton of your program. Requests to reproduce any part of this material may be made to Engineer Your World. Page 3 of 8

4 Before we begin coding the pushbutton, we have to tell the Arduino which pins are used for output and input. We didn t have to do this before because all the pins were being used as output pins (Pin 12 was connected to the speaker, which created the output of music). Now, pin 12 is still the output, but pin 3 is the input. You only have to do this once, so type the following two lines in the void setup()part of the program. pinmode(speakerpin,output); pinmode(buttonpin,input_pullup); The command pinmode sets each pin as an output or an input. For more information, see Arduino references online. Encourage students to take notes of the new commands learned for the push button. These commands will be essential in the following unit, Systems Engineering: Aerial Imaging. Your screen should look similar to the following: STEP 3: IMPORT EXISTING MUSICAL CODE. 1. Open the file lesson4samplemusic.ino. This file contains sample music for this lesson. This file is found in the zip folder U06_L04_05-Sample_Code.zip. Direct your students to open the file they made in Lesson 3. Since we are going to want this music to play anytime we push the button, we need to place it in the void loop() part. Have students copy and paste the part of their code with the music notes into the void loop section of the program. Make sure they copy and paste all variable declarations as well. The program should similar to the following screenshot. Requests to reproduce any part of this material may be made to Engineer Your World. Page 4 of 8

5 2. Save it as a new program. We will save it as lesson4.ino. Instruct students to save as a new file. Confirm that students have completed this step. STEP 4: PROGRAMMING THE PUSHBUTTON WITH AN IF-STATEMENT REMINDER: For our program, we will want the song to play anytime the button is pressed. Therefore, we should insert the code that controls the pushbutton in the void loop()portion of our code. Requests to reproduce any part of this material may be made to Engineer Your World. Page 5 of 8

6 Conditional Programming We want the speaker to play music only IF we press the button. Programmers use conditional programming to control outputs. The code used is similar to written English, but it involves some extra syntax: Write this portion of code on the board, and have students write it in their notebooks: if(test condition) { //code to execute } For most test conditions, your students will more than likely need the program to compare the value of variable to a specific number (e.g., x has to be equal to 10). To code these comparisons, the following comparison operators are used: Comparison Operators: = = (equal to)!= (not equal to) < (less than) > (greater than) <= (less than or equal to) >= (greater than or equal to) The students will need these symbols for future programming. We want to test if the button has been pressed. If it has, that means that Pin 3 is connected to ground and will be LOW. Note: You may want students to refer to the schematic diagram to verify this. We can test this with the following code: if(digitalread(3) == LOW) { //code to execute; } The command digitalread(3) == LOW will read pin 3 to check if it is connected to ground. If it is, this means the push button is pressed and a connection with ground has been made. Notice that digitalread is reading the state of Pin 3 and testing if it is LOW by using the double equals sign (==). If this statement is true, the code in the curly braces will execute. If it is not true (i.e. Pin 3 == HIGH), the code will not execute. Finally, the code to execute inside the curly braces is the code that contains the music. Instruct students to place the if statement and the curly braces around the musical code in the void loop()portion of our code. The void loop()part should look similar to the following screenshot: Note: There are two curly braces not shown here: one closes the if-statement, the other closes the void loop(). Requests to reproduce any part of this material may be made to Engineer Your World. Page 6 of 8

7 STEP 5: COMPILE, UPLOAD, AND PLAY THE SONG. The song won t play unless you press the button. Make sure to review the code with the students so that they understand what segments of code control the pushbutton, the speaker, and the music. STEP 6: PROGRAMMING THE PUSHBUTTON WITH A WHILE LOOP Students can also use the pushbutton with a while-loop. A while-loop will execute forever as long as its conditions are true. For instance, we could want the speaker to be on while the button is pressed, and off if it is not. The following syntax is used for while-loops: Requests to reproduce any part of this material may be made to Engineer Your World. Page 7 of 8

8 while(test condition) { //code to execute; } So for the example, we could use the following code in the void loop()section : while (digitalread(buttonpin) == LOW) { tone(speakerpin,262); } Once the button is released, turn the speaker off with: notone(speakerpin); This program should now look like the following screenshot: Encourage students to be creative in incorporating the pushbutton. Examples of creative uses are playing one song with multiple harmonies, playing a canon or a round of music amongst groups, or using the button as a disk jockey would. Requests to reproduce any part of this material may be made to Engineer Your World. Page 8 of 8