Final code

Wire it

• All the wiring from Steps 1–5 is in place: IN1–IN4 on pins 8–11, HC-05 TXD → pin 7 and RXD → pin 6.

✔ All ticked. Now upload the code.

Upload the code

1. Close the Serial Monitor if it is open.
2. Download the sketch below and open it in Arduino IDE (File → Open). If the IDE asks to put it in a folder, click OK.
3. Plug the USB cable back in. Check Tools → Board says Arduino UNO and Tools → Port shows your COM port.
4. Click Upload (the round → arrow button). Wait for Done uploading.

// Eazytronic.com

#include <SoftwareSerial.h>
SoftwareSerial mySerial(7,6); // {tx,rx}
void setup()
{
  Serial.begin(9600);
  mySerial.begin(9600);
  pinMode(8,OUTPUT);
  pinMode(9,OUTPUT);
  pinMode(10,OUTPUT);
  pinMode(11,OUTPUT);

  digitalWrite(8,HIGH);
  digitalWrite(9,HIGH);
  digitalWrite(10,HIGH);
  digitalWrite(11,HIGH);
}
void loop ()
{
  if (mySerial.available () >0)
  {
    char data = mySerial.read();
    Serial.println(data);

    if ( data == 'A') { digitalWrite(8,HIGH); }
    if ( data == 'B') { digitalWrite(8,LOW); }
    if ( data == 'C') { digitalWrite(9,HIGH); }
    if ( data == 'D') { digitalWrite(9,LOW); }
    if ( data == 'E') { digitalWrite(10,HIGH); }
    if ( data == 'F') { digitalWrite(10,LOW); }
    if ( data == 'G') { digitalWrite(11,HIGH); }
    if ( data == 'H') { digitalWrite(11,LOW); }
  }
}

Make phone buttons

In Serial Bluetooth Terminal, the row of buttons (M1, M2 …) above the keyboard are macro buttons. Long-press one to edit it: type a Name and a Value (the letter), then save. If you need more buttons, look in the app's settings for more macro button rows.

• Light 1 ON = B, Light 1 OFF = A
• Light 2 ON = D, Light 2 OFF = C
• Light 3 ON = F, Light 3 OFF = E
• Fan ON = H, Fan OFF = G

No buttons? You can always just type the letter and tap send.

Command letters