Lab 3 XBees and LCDs and Accelerometers, Oh My! Part 1: Wireless Communication Using XBee Modules and the Arduino

Transcription

1 University of Pennsylvania Department of Electrical and Systems Engineering ESE 205 Electrical Circuits and Systems Laboratory I Lab 3 XBees and LCDs and Accelerometers, Oh My! Introduction: In the first part of this lab, you will learn how to use two XBee modules to transmit and receive information wirelessly. XBee is a brand of low-power radio transmitter/receiver based on the ZigBee digital communication protocol. First, you will program one Arduino board to transmit one byte per second through an XBee module. The other Arduino will receive the byte through an XBee module configured on the same channel as the transmitter, and it will turn a servo left or right based on the identity of the byte. Next, you will use the XBee modules to remotely control an LED on one Arduino with a photoresistor on another Arduino. This is similar to what you did in the last part of Lab 1, except this time, it s WIRELESS! In the second part of this lab, you will learn how to use a LCD (liquid crystal display) screen for text display and other interesting applications. You will first create a timer that shows a countdown and sounds a buzzer after a certain amount of time has elapsed. You will then change the pitch of a buzzer by tilting an accelerometer, while displaying the frequency of the pitch on the LCD screen. Finally, you will use the accelerometer and LCD screen to simulate a spirit-level indicator. Part 1: Wireless Communication Using XBee Modules and the Arduino Figure 1 - Transmitter and Receiver Modules

2 Goal: - To control the motion of a continuous rotation Parallax motor using Arduino communication via XBee. - To control the lighting of an LED with a photoresistor using Arduino communication via XBee. Parts Required 1. 2 Arduino Boards 2. 2 USB Cables 3. 2 XBee Shields 4. 2 XBee Modules 5. 2 Extension Shields 6. Wires 7. Photoresistor 8. Two (2) 1 k resistors 9. LED For this part of the lab, you will be paired up with another group since you must use two Arduino boards. Your group will be assigned two XBee modules and two XBee Arduino shields. Each pair of XBee modules is configured to communicate on a unique channel, so do not accidentally switch one of your XBees with another group. Remote control of a continuous rotation Parallax motor using XBee Procedure: One group (2 people) should set up the receiver (parts a through e) while the other group sets up the transmitter (parts f through g). You will switch roles for the next section. Receiver Module a. Connect the XBee Shield and set the Receiver Arduino module in USB Programming mode Connect the XBee Shield to the Arduino Board as shown in Figure 1 (or Figure 3). Remove the jumpers to set the XBee module in USB programming mode. Please do not lose the jumpers (shown below)! You will need them again in the next step. Figure 2 - Jumpers (DO NOT LOSE!)

3 Figure 3 - Arduino XBee Shield in USB Programming Mode b. Compile and download the working code to the Receiver Arduino module #include <Servo.h> const int ledpin = 13; const int servopin = 12; int incomingbyte; Servo myservo; // the pin that the LED is attached to // the pin that the +5V of servo is attached to // a variable to read incoming serial data into // create servo object to control a servo void setup() { // initialize serial communication: Serial.begin(9600); // initialize the LED pin as an output: pinmode(ledpin, OUTPUT); // initialize the SERVO pin as an output: pinmode(servopin, OUTPUT); // set servopin to +5V

4 digitalwrite(servopin, HIGH); // Pin 10 of the Arduino output is connected to the PWN input of the servo motor myservo.attach(10); void loop() { // see if there's incoming serial data: if (Serial.available() > 0) { // read the oldest byte in the serial buffer: incomingbyte = Serial.read(); // if it's a capital L (ASCII 72), turn on the LED and rotate the servo motor clockwise if (incomingbyte == 'L') { digitalwrite(ledpin, HIGH); myservo.write(0); // if it's an R (ASCII 76) turn off the LED and rotate the servo motor anti-clockwise if (incomingbyte == 'R') { digitalwrite(ledpin, LOW); myservo.write(180); d. Set the Receiver Arduino module in XBee mode Connect the jumpers to the XBee shield, as shown in Figure 4, to set it on XBee mode. This will be the receiver Arduino module.

5 Figure 4 - Arduino XBee Shield in XBee Mode e. Connect one of the Boe-Bot s servos to the receiver Arduino module as shown in Figure 5. Figure 5 - Continuous Rotation Parallax Motor Note: You are using one of the servos on your Boe-Bot platform, not the servo pictured above. Transmitter Module f. Follow step a to set the Transmitter Arduino module in USB Programming mode g. Compile and download the working code to the Transmitter Arduino module

6 void setup() { Serial.begin(9600); // initialize serial communication void loop() { Serial.print('L'); delay(1000); Serial.print('R'); delay(1000); h. Set the Transmitter Arduino module in XBee mode as in step d, by connecting the jumper wires i. Observe the rotation of the servo motor In the Arduino window containing the code for the transmitter, open the serial monitor by pressing the Serial Monitor button to the right of the Upload button. You should see alternating L s and R s appear every second. The servo motor attached to the receiver module will turn clockwise and anticlockwise based on the serial data transmitted from the transmitter module. The LED on the receiver module should blink on and off. Remote control of an LED using a photoresistor circuit and XBee Procedure: The group (2 people) that set up the receiver in the previous part should now set up the transmitter, and the group that set up the transmitter last time should set up the receiver. This part requires you to construct a circuit on both the receiving and transmitting Arduino boards. However, there is no room to fit a breadboard on the Arduino since it is occupied by the XBee shield. For this reason, we have constructed extension shields that can hold a breadboard shield, XBee shield, and LCD screen all on one shield. The only limitation is that each component occupies a number of digital I/O pins; consequently, only two components can be used at a time. In this part of the lab, you will use the extension shield to hold the XBee shield and the breadboard shield. Connect your shields as shown in Figure 6.

7 Transmitter Receiver Figure 6 - Configuration of Arduino Shields on Extension Shield Receiver Module a. Construct the circuit given by the schematic in Figure 7. Figure 7 - Receiver LED circuit b. Set the Arduino in USB Programming mode (remove jumpers) and copy the following code into your window. const int ledpin = 12; // the pin that the LED is attached to int incomingbyte; // a variable to read incoming serial data into void setup() { Serial.begin(9600); // initialize serial communication pinmode(ledpin, OUTPUT); // initialize the LED pin as an output void loop() { // see if there's incoming serial data: if (Serial.available() > 0){

8 // read the oldest value in the serial buffer: incomingbyte = Serial.read(); if(incomingbyte == 'D'){ digitalwrite(ledpin, HIGH); else if(incomingbyte == 'L'){ digitalwrite(ledpin, LOW); c. Set the Arduino in XBee mode by connecting the jumpers. Transmitter Module d. Construct the circuit given by the schematic in Figure 8. Choose any analog pin (0-5). Figure 8 - Transmitter voltage divider circuit e. Set the Arduino in USB Programming mode (remove jumpers) and upload the following code: int analogpin = ***; // change *** to the pin number you're reading from int value; void setup(){ Serial.begin(9600); // initialize serial communication void loop(){ value = analogread(analogpin); if(value >= 150){ // you may need to modify this argument Serial.print('L'); delay(500); if(value < 150){ Serial.print('D'); delay(500);

9 f. Set the Transmitter Arduino in XBee mode by connecting the jumpers. g. Demonstrate to a TA that your system works! Thinking Further Biomedical application With technology rapidly evolving, it is becoming possible for medical professionals to remotely observe and treat patients. This new form of medicine, called telemedicine, allows people in need of medical surveillance to move around comfortably at home while their physiological signals, such as heart rate, brain and muscle activity, etc., are wirelessly transmitted to a computer and sent to a medical center to be analyzed. Imagine a digital communication system consisting of two XBee modules (one transmitter and one receiver), two Arduinos, and a biomedical sensor such as an electrocardiograph (ECG), which records electrical currents associated with heart muscle activity (shown in Figure 9). The signal from the ECG is directly connected to the transmitter, which then wirelessly transmits the signal to the receiver. The data can then be transferred from the receiver onto a computer and sent to a medical center via an internet connection. With your group, briefly discuss the following: - What are some factors that might interfere with the quality of the transmitted signal? - Do you think that this could be an effective system for remote patient monitoring? - Could a similar type of system be used by a doctor to remotely treat a patient? Figure 9 - Electrocardiograph ( Part 2: Applications of LCD Screen and Accelerometer

10 Parts Required: 1. Arduino Board 2. USB Cable 3. Sound Buzzer 4. 16X2 LCD Display 5. ADXL335, 3-axis Accelerometer 6. Wires Self-Timer using the Arduino Procedure: a. Building the circuit Attach the LCD screen shield to the Arduino, and place the breadboard shield on top, as shown in Figure 10. Build the sound buzzer circuit as described in Figure 11. Figure 10 - Arduino Shield Configuration Figure 11 - Sound Buzzer Circuit 6 b. Compile and download the following working code to the Arduino Board using Arduino IDE.

11 #include <LiquidCrystal.h> // initialize the library with the numbers of the interface pins LiquidCrystal lcd(12, 11, 13, 10, 9, 8); int runtimer = 1; // true condition for timer int serialdata = 0; // false condition for serial communication int speakerpin = 6; int data = 0; // default condition void setup() { pinmode(speakerpin, OUTPUT); // set up the LCD's number of rows and columns: lcd.begin(16, 2); void loop() { // To execute timer only once if(runtimer == 1){ // Print a message to the LCD. lcd.clear(); lcd.print("timer: "); //Start timer timer(); // runs the timer code below, under void timer() runtimer = 0; lcd.nodisplay(); delay(250); // Sound Buzzer for(int duration = 0; duration < 100; duration ++){ digitalwrite(speakerpin, HIGH); delaymicroseconds(2000);

12 digitalwrite(speakerpin, LOW); delaymicroseconds(2000); lcd.display(); delay(250); void timer(){ // For loop to run the COUNT-DOWN in Seconds for(int timer = 10; timer > 0; --timer){ // Set the Cursor to the space after the display "TIMER: " if(timer >= 10) lcd.setcursor(6,0); else{ lcd.setcursor(6,0); lcd.print("0"); lcd.setcursor(7,0); // Display the COUNT-DOWN Seconds lcd.print(timer); lcd.print("s"); delay(1000); // Bring the Cursor to the initial position lcd.setcursor(0,0); lcd.clear(); lcd.print("buzzer!"); c. Self-Timer and Sound Buzzer

13 Press the RESET Button of the Arduino board, the timer will countdown from 10 seconds, as programmed. Once the timer countdown reaches 0s, the buzzer will go on and the LCD display will blink Buzzer! The program is reset every time you press the RESET Button of the Arduino board and the timer countdown begins again. d. Questions i. Can you make the timer countdown from 100 seconds? ii. Can you make the buzzer buzz only for a fixed amount of time after the timer countdown reaches 0s? Show a TA! Possibly helpful reference links: Pitch-Control Using an Accelerometer and the Arduino Procedure: a. 3-Axis Accelerometer An accelerometer is used to measure the acceleration experienced by an object. The ADXL335 (Figure 12) is adopted to measure the acceleration experienced by the object in motion with respect to the X or Y or Z axis. We will only be measuring movements to the Y axis in this lab. b. Interface the 3-Axis Accelerometer Figure 12 - ADXL335, 3-axis Accelerometer Connect the 3-Axis accelerometer to the Arduino shield as shown in Figure 13. Keep your buzzer circuit from the previous part connected.

14 Figure 13 Interfacing ADXL335, 3-Axis Accelerometer, with the Arduino Board c. Copy the following code into the Arduino IDE (the code will not compile correctly until you change *** with numbers): #include <LiquidCrystal.h> // initialize the library with the numbers of the interface pins LiquidCrystal lcd(12, 11, 13, 10, 9, 8); const int groundpin = 14; const int powerpin = 18; const int buzzerpin = 6; const int ypin = 16; // analog input pin0 -- ground // analog input pin4 -- voltage // digital input pin6 -- buzzer // analog input pin2 -- y-axis pin int yvalue; int freq; int ymin = ***; int ymax = ***; // Replace with measured minimum yvalue // Replace with measured maximum yvalue void setup() { pinmode(buzzerpin, OUTPUT); pinmode(groundpin, OUTPUT); pinmode(powerpin, OUTPUT); digitalwrite(groundpin, LOW); digitalwrite(powerpin, HIGH); // set up the LCD's number of rows and columns:

15 lcd.begin(16, 2); void loop() { yvalue = analogread(ypin); freq = map(yvalue, ymin, ymax, 100, 10000); // maps yvalue into frequency range tone(buzzerpin, freq); // sounds buzzer at given frequency lcd.clear(); lcd.setcursor(0,0); lcd.print("freq: "); lcd.print(freq); lcd.print(" Hz"); lcd.setcursor(0,1); lcd.print("yvalue: "); lcd.print(yvalue); delay(150); d. Find the range of the y-axis acceleration Find the minimum and maximum values of the y-axis acceleration (yvalue). Replace the values of ymin and ymax with the values you found. Upload the code to the Arduino and tilt the board along the y-axis to observe its effect. The map function map(value, fromlow, fromhigh, tolow, tohigh) maps a value of fromlow to tolow, a value of fromhigh to tohigh, values in-between to values in-between, etc. In this case, yvalue is converted from an acceleration value to a frequency value. To get more information about any function, right-click the function name and click Find in Reference. e. Questions i. If yvalue is 450, then what is the value of freq? ii. How would you change the range of frequencies that is swept through? iii. Can you modify the code so that change of pitch sounds more continuous? iv. Change the code so that the change in frequency correlates with acceleration on the x- axis instead of the y-axis? Show a TA!

16 Spirit-Level Indicator using the Arduino Procedure: a. Compile and download the working code to the Arduino Board: #include <LiquidCrystal.h> LiquidCrystal lcd(12, 11, 13, 10, 9, 8); const int groundpin = 14; const int powerpin = 18; const int ypin =2; // analog input pin0 -- ground // analog input pin4 -- voltage // y-axis of the accelerometer void setup() { lcd.begin(16, 2); Serial.begin(9600); pinmode(groundpin, OUTPUT); pinmode(powerpin, OUTPUT); digitalwrite(groundpin, LOW); digitalwrite(powerpin, HIGH); void loop() { int avalue = 0; int lcd_cursor_position = 0; lcd.clear(); avalue = analogread(ypin); lcd_cursor_position = 46 - avalue/13; Serial.print(avalue); // read value of the X-axis acceleration // calculation to position the lcd cursor // prints x-axis acceleration in serial monitor lcd.setcursor((15 - lcd_cursor_position), 1); lcd.print('.'); lcd.setcursor((15 - lcd_cursor_position), 0); lcd.print('.'); delay(100);

17 b. Questions: v. Make the spirit level indicator. move in the direction of the acceleration. vi. Make one spirit level indicator. move in the opposite direction to the other. Show a TA! vii. Extra Credit: Using a sound buzzer, play any musical note, if the level indicator is stationary in a particular position for more than 10 seconds. Show a TA!