Beginners Guide to Magic Bit¶

In this guide we are learning how to use the basic components on the Magic Bit board. The components comes with the Magic Bit is arranged as following. We have provided code examples as well as self assignment set to enhance your knowledge.

https://github.com/magicbitlk/Magicbit-Arduino/raw/master/Resources/Layout.png

Example 1: Blinking an LED¶

Introduction¶

In this example you are learning how to turn on and off a LED or any other actuator which can be controlled by a digital output such as relay, bulb, motor.

Learning Outcomes¶

From this example, you’ll get an understanding about,

Pin Mode
Digital Write
Delay Functions

Components¶

Magic Bit

Theory¶

A digital output allows you to control a voltage with an electronic device. If the device instructs the output to be high, the output will produce a voltage (generally about 5 or 3.3 volts). If the device instructs the output to be low, it is connected to ground and produces no voltage.Here magicbit is the device and output voltage is either 3.3V for HIGH and 0V for LOW.

Methodology¶

Magicbit equipped with four onboard leds in magicbit development board, Lets select yellow LED (which is wired to D18)

By setting output state to high of LED pin will turn on the led and by setting output state to LOW will turn of LED.

Coding¶

void setup(){
   pinMode(18,OUTPUT);
}
void loop(){
   digitalWrite(18,HIGH);
   delay(1000);
   digitalWrite(18,LOW);
   delay(1000);
}

Explanation¶

pinMode(pin, Mode): Configures the specified pin to behave either as an input or an output. Here we use pin as an output

digitalWrite(pin No, State): Write a HIGH or a LOW value to a digital pin.Pin mode must be setup for the same pin in Setup to work this function properly.

delay(ms): Pauses the program for the amount of time (in milliseconds) specified as parameter.(note 1000 milliseconds equals to one second)

Activity¶

Write code for a knight rider pattern using on board leds of magicbit

Example 2: Reading the state of a push button¶

Introduction¶

In this example you are learning how read a digital input from something like a button & use it to turn on and off a LED or any other digital device.

Learning Outcomes¶

From this example, you’ll get an understanding about,

Digital Read
IF-ELSE conditions
Variables

Components¶

Magic Bit

Theory¶

A digital input allows you to read digital signals. Microcontroller recognizes the signal as 1(HIGH) when the signal is close to 3.3v (or 5v depending on the microcontroller) and recognizes as 0(LOW) when the signal is close to 0v. This reading can be used in the program to do various things.

Methodology¶

Magicbit equipped with two onboard push buttons in magicbit development board, Lets select the push button which is wired to D34. Buttons on the board are in pulled up internally (to learn more about pullups/pulldowns follow this link), which means when button is not pressed the status of the button is 1(HIGH), & when the button is pressed the status of the button is 0(LOW).

Also like in previous example we need to select an LED to indicate the change, lets select RED LED which is wired to pin D27.

First we set the input output configurations of the Button and the LED using pinMode, in this case button is an INPUT, LED is an OUTPUT. Then in the loop section we check the state of the button & store it in an int type variable called buttonState (follow this link to learn more about data types in arduino).

Then we can use the variable as the condition of the if block, and if the button is pressed, the bulb should turn on, and the button is not pressed the light should turn off.

Coding¶

void Setup(){
   pinMode(27,OUTPUT);
   pinMode(34,INPUT);
}
void loop(){

 int buttonState = digitalRead(34);
 if(buttonState == LOW){
   digitalWrite(27, HIGH);
 }else{
   digitalWrite(27, LOW);
 }
}

Explanation¶

digitalRead(pin No): Reads the condition of the given pin and returns a digital value HIGH or LOW.

IF/ELSE: Used to evaluate a digital condition, we can put a digital logic condition in then parenthesis. If the condition is true, it executes the code block in the immediate curly bracket section, if the condition is false it executes the code block in the else curly bracket.

if(condition){

//Do if condition is true

}else{

//Do if condition is false

}

Activity¶

Write a code to toggle an LED in the button press. LED turns on when button pressed & released, LED turns off when button is pressed & released again. (Hint: Make use of variables to ‘remember’ the state of the button press).

Example 3: Working with Analog Write¶

Introduction¶

In this example you are learning how to turn on and off a LED or any other actuator which can be controlled by a digital output such as relay, bulb, motor.

Learning Outcomes¶

From this example, you’ll get an understanding about,

Pulse Width Modulation
Analog Write

Components¶

Magic Bit

Theory¶

To change the brightness of a LED we could change the voltage the LED is supplied with, but in a microcontroller, ability to change the voltage (converting a digital number to an analog voltage) is limited, so a method called PWM (Pulse Width Modulation) is used. What this does is pulsing on and off the pin in a high frequency. The length of the pulses creates the perception of brightness.

Duty cycle is a term used to describe the ratio between on and off times.

In this example higher Duty cycle gives higher brightness & lower duty cycle gives lower brightness.

Methodology¶

Lets select green LED (which is wired to D16). We will use a for loop to generate the duty cycle (0 - 0% duty, 255-100% duty). And also to generate 255 cycles.

Coding¶

#include <ESP32Servo.h>

void setup(){
      pinMode(16,OUTPUT);
}
void loop(){
      for(int i = 0; i < 256; i++){
      analogRead(16, i);
      delay(10);
}

Explanation¶

for(int i=0; i<256; i++): There are 3 parameters in a for loop, first parameter we are defining a variable to store the value generated by the for loop. Second parameter specifies the condition that needs to be true to run the for loop(else it breaks out from the loop), third parameter specifies the change happens to the variable in each cycle, in this case 1, added to i.

analogWrite(pin number, pwm value): You can input the pin number you need to do pwm and then the pwm value you need to give to that pin. This assigns the corresponding duty cycle to the pin.

Activity¶

This example we have coded to increase the brightness, write a code to do the opposite of that, to fade the brightness of the led, & put both effects together to create a beautiful fade & light up effect.

Example 4: Using Serial Protocol¶

Introduction¶

In this example you are learning to use serial communication function.

Learning Outcomes¶

From this example, you’ll get an understanding about,

Serial Protocol usage between Magic Bit & the PC

Components¶

Magic Bit
Computer with arduino installed

Theory¶

In microcontroller programming, communication between devices is essential. There are hundreds of protocols available, but most common & easy to use is Serial Protocol. Commonly used to communicate information between a microcontroller and a computer.

Methodology¶

We configure a button as the 2nd example (D34 is used). Then we initialize serial communication between the computer and magic bit. After that in the loop section if condition check if the button is pressed. If pressed, it prints “Button Pressed” on the serial console.

You could use the serial monitor window of arduino IDE to view the serial output

Then the serial console appears (you have to select the serial port number correctly, follow this link to learn how to).

1: You can type in stuff here & hit enter to send data to magic bit

2: This area shows the data coming from magic bit

3: From this menu you have to select a common baudrate between the computer and the magic bit.

Coding¶

void setup(){
  pinMode(34,INPUT);
  Serial.begin(9600);
}
void loop(){
  if(digitalRead(34) == LOW){
    Serial.println(“Button is Pressed”);
  }
}

Explanation¶

Serial.begin(baudrate): Initializes a serial connection, baudrate specifies the speed of data transfer (bits per second). Standard values are 1200, 2400, 4800, 9600, 14400, 19200, 38400, 57600, 115200, 128000 and 25600

Serial.print(stuff to print): Using this function, serial data can be sent, stuff to print can be any type of arduino variable, or even a static string.

Serial.println(stuff to print): Using this function, serial data can be sent, stuff to print can be any type of arduino variable, or even a static string, this is different than Serial.print() is this always prints the content in a new line, rather than printing all in one line.

Activity¶

do the same example using Serial.print(), observe the difference. Create a button press counter, which displays the button press count on the serial console of arduino IDE.

Example 5: Reading an Analog Signal¶

Introduction¶

In this example you are learning to read an analog sensor & print it on the serial console.

Learning Outcomes¶

From this example, you’ll get an understanding about,

Analog Read function

Components¶

Magic Bit

Theory¶

In real world most of the signals we encounter are analog signals (temperature, air pressure, velocity), they are continuous. But computers work on digital domain, to interact between the worlds, representing an analog signal in the digital domain is important. (to read more about analog to digital conversation, follow this link)

Methodology¶

For this example we use the potentiometer on the magic bit board, which is connected to pin, D39. It generates a voltage between 0 and 3.3V according to the angle of the potentiometer.

We read the analog signal and storing it in an int type variable(0v= 0 analog value, 3.3v = 1024 analog value), sensorValue, later, we use this value to print on the serial window of arduino IDE as well as light up the red LED(D27) if the analog value exceeds than 512.

Coding¶

void setup(){
     pinMode(39,INPUT);
     pinMode(27,OUTPUT)
     Serial.begin(9600);
}
void loop(){
     int sensorValue = analogRead(39);
     Serial.println(sensorValue);

     if(sensorValue > 512){
        digitalWrite(27,HIGH);
     }else{
        digitalWrite(27,LOW);
     }
 }

Explanation¶

analogRead(pin No): this reads and assigns the corresponding analog value to the left.

Activity¶

Do the same example using the LDR on the board (D36)

Example 6: Generating Tones¶

Introduction¶

In this example you are learning to generate a tone using the onboard buzzer on the magicbit.

Learning Outcomes¶

From this example, you’ll get an understanding about,

Tone Function

Components¶

Magic Bit

Theory¶

Piezo buzzers are commonly used in embedded systems to give audible tones. Combined with ESPservo library magic bit can generate various tones. (Follow this link to know how to install ESPservo library)

Methodology¶

For this example we use the piezo buzzer wired to pin 25 of the Magic Bit.

ESP32Servo.h library is used to generate pwm signals needed to generate tones. We could specify the frequency & duration of the tone.

Coding¶

#include <ESP32Servo.h>
void Setup(){
   pinMode(25,OUTPUT);
}
void loop(){
   tone( 25 ,4186,500); //C Note
   delay(1000);
   tone( 25,5274,500); //E Note
   delay(1000);
}

Explanation¶

tone(pin No, frequency, duration): generates pwm to corresponding to the given parameters

Activity¶

Create a program that plays one frequency when one push button on the board pressed, and another frequency when the other push button when pressed.

Example 7: Using the onboard OLED Screen¶

Introduction¶

Color OLED screen on Magic Bit can display text as well as simple logos & images.

Learning Outcomes¶

From this example, you’ll get an understanding about,

Using Adafruit OLED library

Components¶

Magic Bit

Theory¶

Magicbit has a 0.96” OLED Screen which can be communicated with from I2C protocol. The display has the address, 0x3c.

Methodology¶

Adafruit OLED library(Adafruit_SSD1306 & Adafruit_GFX) is used to handle the LCD, its important to install those libraries beforehand. First we create the content we need to print onto the screen and then use display.display command to update the screen.

Coding¶

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#define OLED_RESET 4

Adafruit_SSD1306 display(128,64);

void setup(){
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.display();
  delay(3000);
}


void loop(){
  display.clearDisplay();
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(10, 0);
  display.println("Hello");

  display.setTextColor(WHITE);
  display.setTextSize(1);
  display.setCursor(0, 25);
  display.println("Welcome to");
  display.println();
  display.println("Magic");
  display.println("Bit");
  display.display();
  display.clearDisplay();

  delay(1000);

  }

Explanation¶

display.clearDisplay(): Clears the OLED display.

display.setTextSize(2): Set the font size of the text.

display.setCursor(0, 25): Sets the cursor(determines where the next text will appear).

display.println(stuff to print): print the data given on a new line, similar effect like Serial.println.

display.setTextColor(WHITE): Sets the color of the text.

display.display(): Updates the changes to the screen.

Activity¶

Make a program to display the ADC value of the potentiometer on the OLED display.