Week 13

This week was a very informative one. Most of the information that was presented was new to me and I liked learning about different communication methods. The assignment was to design, build, and connect wired or wireless node(s) with network or bus addresses. There was a group assignment to send a message between two projects but, unfortunately, under the current circumstances this would've taken more time than we could afford.

I chose to use the nRF24L01 module which a transceiver module that can send and receive data. The original idea was to control the servo with the joystick control used in several previous assginements. However, I really wanted to try connecting a keypad and learn how to use it.

Individual assignment

Like mentioned above, I used a keypad to communicate with an LCD that is connected to a differen't Arduino. I'll try to go throught the steps of connecting the two devices wirelessly via nRF24L01.

The photo above show the devices we want to connect. The communication will be done through 2 Arduino Unos. The arduino set up is shown in the photo below.

I will now go through the exact detaild on how the LCD was connected as this was covered in another project. Also, the keypad connection is straight forward. I used the library shown below to read the data from the keypad.

Keypad connection. Source: circuitbasics.com/

The button on the keypad are connected in a 4x4 matrix and each button has a column number and a row number. This is why a 4x4 keypad takes 8 pins on the arduino.
The library (shown below) does a great job organizing the pins and the buttons.

That's all it takes to connect these devices to the arduinos. Now comes the part where we will have to send data between the two arduinos. The nRF24L01 uses SPI connection to connect to the arduino. The wiring is shown below:

VCC is connected to a 3.3V source. SCK, MOSI, MISO are connected to 13, 11, 12, respectively. the two remaining pins are CSN and CE and they can be connected to any user-specified digital pin. They will have to be assigned in the code later.
After connecting the modules on both arduinos, it's time to write the code for each one. One will be the TX (transmitter) code and the other will be the RX (received) code.

First, RF24 library was installed to Arduino IDE. Then I took the code from https://www.elec-cafe.com/arduino-wireless-temperature-lcd-display-nrf24l01-dht11/ and changed it to fit my project.

Transmitter code:

#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>
#include <Keypad.h>

RF24 radio(9, 10); // CE, CSN         
const byte address[6] = "00001";     //Byte of array representing the address. This is the address where we will send the data. This should be same on the receiving side.

//*** -----  this is the bit for the keypad -------***//

const byte ROWS = 4; //four rows
const byte COLS = 4; //four columns
//define the cymbols on the buttons of the keypads
char hexaKeys[ROWS][COLS] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};
byte rowPins[ROWS] = {0,2,3,4}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {5,6,7,8}; //connect to the column pinouts of the keypad

//initialize an instance of class NewKeypad
Keypad customKeypad = Keypad( makeKeymap(hexaKeys), rowPins, colPins, ROWS, COLS);

//**----- end of keypad bit -----**//

void setup() {
Serial.begin(9600);
radio.begin();                  //Starting the Wireless communication
radio.openWritingPipe(address); //Setting the address where we will send the data
radio.setPALevel(RF24_PA_MIN);  //You can set it as minimum or maximum depending on the distance between the transmitter and receiver.
radio.stopListening();          //This sets the module as transmitter
}
void loop()
{

char customKey= customKeypad.getKey(); //reads the pressed key
if (customKey){
  Serial.println(customKey);
  radio.write(&customKey, sizeof(customKey));  // sends the data via nRF24L01
}

delay(1000);
}

Receiver code:

#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>
#include <Wire.h> 
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x3F,16,2); // LCD I2C address, columns, rows.

RF24 radio(9, 10); // CE, CSN     // pins connecred to the nRF24L01    
const byte address[6] = "00001";     //Byte of array representing the address. This is the address where we will send the data. This should be same on the receiving side.
bool newData=false;
char customKey;

void setup() {
lcd.init();
lcd.backlight();
Serial.begin(9600);
radio.begin();                  //Starting the Wireless communication
radio.openReadingPipe(1,address); //Setting the address where we will send the data
//radio.setPALevel(RF24_PA_MAX);  //You can set it as minimum or maximum depending on the distance between the transmitter and receiver.
radio.startListening();          //This sets the module as receiver
}
void loop()

{
if (radio.available()){

radio.read(&customKey, sizeof(customKey));  //Reads the received data
newData = true;
}

if (newData==true) {
  
  lcd.clear();
  delay(500);
  lcd.setCursor(0,0);
  lcd.print(customKey);
  Serial.println(customKey);
  delay(1000);
  newData=false;
}

else

{
  newData=false;
  lcd.setCursor(0,0);
  lcd.print("no number");
  Serial.println("no number");
  delay(1000);
}
}

Here is a video showing the final result of the assignment:

Sending numbers to LCD via nRF24

Lessons learned

There were some hiccups along the way while trying to figure out how to do this assignment. I had to look at multiple examples in order to learn how to use the library properly. Also, I still need to learn how to send mupltiple digits to use, for example, as passkey. The assignment currently sends 1 character at a time.
I will try to connect a servo and control it via nRF24 just to keep improving the assignments i've been working on.