14. Networking and communications¶

This week I experimented with simple networking.

Bluetooth¶

I decided to use an HC-05 Bluetooth module, and set it up so I can communicate with it using my phone.

AT Commands¶

In order to use the HC-05 module, it should first be configured using AT Commands, the list is below.

Command	Function
AT+RMAAD	Clears previously paired devices
AT+ROLE	Sets it as slave 0 or master 1
AT+ADDR	Gets the address of the module
AT+UART	Sets the baud rate
AT+PSWD	Changes the password of module

After each command add a “?” or to obtain/change the value

To actually enter the AT commands, I uploaded this program to the board, it will send the commands to the module (pins 10 and 11) and print its response back in the regular serial port. The pins were connected like this:

VCC (3.3V in Arduino) —> VCC
Using 5V will probably damage the module, but it worked fine for me…
GND —> GND (It should be disconnected when uploading the sketch)
RX —> PA2 (pin 5 in ATTiny412)
TX —> PA3 (pin 7 in ATTiny412)
EN —> PA7 (pin 3 in ATTiny412)

/*

AUTHOR: Hazim Bitar (techbitar)
DATE: Aug 29, 2013
LICENSE: Public domain (use at your own risk)
CONTACT: techbitar at gmail dot com (techbitar.com)

*/
#include <SoftwareSerial.h>

SoftwareSerial BTSerial(A2, A3); // RX | TX

void setup()
{
  pinMode(PA7, OUTPUT);  // this pin will pull the HC-05 pin 34 (key pin) HIGH to switch module to AT mode
  digitalWrite(PA7, HIGH);
  Serial.begin(9600);
  Serial.println("Enter AT commands:");
  BTSerial.begin(38400);  // HC-05 default speed in AT command more
}

void loop()
{
  // Keep reading from HC-05 and send to Arduino Serial Monitor
  if (BTSerial.available())
    Serial.write(BTSerial.read());

  // Keep reading from Arduino Serial Monitor and send to HC-05
  if (Serial.available())
    BTSerial.write(Serial.read());
}

Using the serial monitor, with Both NL & CR selected, I entered the commands and this was the result:

Main program¶

I then cross-connected the TX and RX pins of the board and HC-05 as before to communicate.

// Max GH 18.05.2022
#include <SoftwareSerial.h>

SoftwareSerial BTSerial(A2, A3);
String incomingString;   // for incoming serial data

void setup() {
        Serial.begin(38400);     // serial communication begins
        BTSerial.begin(38400);
}

void loop() {

        // send data only when you receive data:
        if (BTSerial.available() > 0) {
                // read the incoming byte
                incomingString = BTSerial.readString();

                // printing using regular Serial pins
                Serial.print("I received: ");
                Serial.println(incomingString);

                // sending it back to the app
                BTSerial.print("I received: ");
                BTSerial.println(incomingString);
        }
}

Sending/receiving data¶

I used Arduino bluetooth controler for android, which allows me to send data through bluetooth. The paired devices will show up in the main menu, selecting MAX_BT, I entered the Terminal mode, which essentially just sends strings.