Bluetooth Volume Control For An Old Stereo With Buttons!

How about getting rid of that broken volume knob on your stereo and replacing it with some buttons, LEDs and Bluetooth?

Oct 12, 2021

•

6286 views

•

4 respects

audio

repair

remote control

Components and supplies

Breadboard (generic)

2x2 Female Header Connector

Arduino UNO

Resistor 100k ohm

Male/Male Jumper Wires

DIP-8 socket

Resistor 100 ohm

Resistor 2.21k ohm

Capacitor 100 nF

HC-06 Bluetooth Module

LED (generic)

Universal PCB

Tactile Switch, Top Actuated

ATtiny85

Resistor 1k ohm

Tools and machines

Solder Flux, Soldering

Desoldering Pump, Metal

Soldering iron (generic)

Solder Wire, 40/60

Apps and platforms

Arduino IDE

Project description

Code

Volume control program for the Attiny

arduino

A program that simulates the rotary encoder by sending appropriate volume up and down signal cycles and communicates with a Bluetooth module to receive "volume up" and "volume down" messages from it.

1//THIS IS FOR ATTINY85 ONLY!
2#include <SoftwareSerial.h>  //Software   Serial Port
3
4//vol cntrl pins
5#define VOL_A 0
6#define VOL_B 1
7
8//buttons   pin
9#define BTNS A1
10
11//bluetooth pins
12#define RxD 3
13#define TxD 4
14
15//bluetooth   connection
16SoftwareSerial blueToothSerial(RxD,TxD);
17
18//signal segment timing   (ms)
19#define SIGNAL_DELAY 80
20
21//it takes ~64 cycles to take the volume   from min to max
22
23void setup() {
24  //init buttons
25  pinMode(BTNS, INPUT);
26   
27  //init volume outputs
28  pinMode(VOL_A, OUTPUT);
29  pinMode(VOL_B, OUTPUT);
30   digitalWrite(VOL_A, HIGH);
31  digitalWrite(VOL_B, HIGH);
32
33  //init BT
34   pinMode(RxD, INPUT);
35  pinMode(TxD, OUTPUT);
36  setupBlueToothConnection();
37}
38
39void   loop() {
40  //read buttons state & send appropriate signals to the stereo
41   int btnState = analogRead(BTNS);
42  if(btnState < 300) {
43    volDown();
44   } else {
45    if(btnState < 700) {
46      volUp();
47    }
48  }
49
50   //read remote commands over BT & send appropriate signals to the stereo
51  char   recvChar;
52  while (blueToothSerial.available() > 0 ) {
53    recvChar = blueToothSerial.read();
54     if (recvChar == '1') {
55      volUp();
56    } else {
57      if (recvChar   == '2') {
58        volDown();
59      }
60    }
61  }
62}
63
64void volDown()
65{
66   digitalWrite(VOL_B, LOW);
67  delay(SIGNAL_DELAY);
68  digitalWrite(VOL_B, HIGH);
69   digitalWrite(VOL_A, LOW);
70  delay(SIGNAL_DELAY);
71  digitalWrite(VOL_A, HIGH);
72   delay(SIGNAL_DELAY);
73}
74
75void volUp()
76{
77  digitalWrite(VOL_A, LOW);
78   delay(SIGNAL_DELAY);
79  digitalWrite(VOL_A, HIGH);
80  digitalWrite(VOL_B,   LOW);
81  delay(SIGNAL_DELAY);
82  digitalWrite(VOL_B, HIGH);
83  delay(SIGNAL_DELAY);
84}
85   
86void setupBlueToothConnection()
87{
88  blueToothSerial.begin(9600); //using   the default baud rate of HC-06
89  blueToothSerial.print("AT+NAMEdupa1"); //set   the name - in fact it would be enough to do it just once, also a reset is needed   after the change
90
91  delay(2000); //a delay just to make sure that the setup   is completed
92  blueToothSerial.flush();
93}
94

//THIS IS FOR ATTINY85 ONLY!
#include <SoftwareSerial.h>  //Software   Serial Port

//vol cntrl pins
#define VOL_A 0
#define VOL_B 1

//buttons   pin
#define BTNS A1

//bluetooth pins
#define RxD 3
#define TxD 4

//bluetooth   connection
SoftwareSerial blueToothSerial(RxD,TxD);

//signal segment timing   (ms)
#define SIGNAL_DELAY 80

//it takes ~64 cycles to take the volume   from min to max

void setup() {
  //init buttons
  pinMode(BTNS, INPUT);
   
  //init volume outputs
  pinMode(VOL_A, OUTPUT);
  pinMode(VOL_B, OUTPUT);
   digitalWrite(VOL_A, HIGH);
  digitalWrite(VOL_B, HIGH);

  //init BT
   pinMode(RxD, INPUT);
  pinMode(TxD, OUTPUT);
  setupBlueToothConnection();
}

void   loop() {
  //read buttons state & send appropriate signals to the stereo
   int btnState = analogRead(BTNS);
  if(btnState < 300) {
    volDown();
   } else {
    if(btnState < 700) {
      volUp();
    }
  }

   //read remote commands over BT & send appropriate signals to the stereo
  char   recvChar;
  while (blueToothSerial.available() > 0 ) {
    recvChar = blueToothSerial.read();
     if (recvChar == '1') {
      volUp();
    } else {
      if (recvChar   == '2') {
        volDown();
      }
    }
  }
}

void volDown()
{
   digitalWrite(VOL_B, LOW);
  delay(SIGNAL_DELAY);
  digitalWrite(VOL_B, HIGH);
   digitalWrite(VOL_A, LOW);
  delay(SIGNAL_DELAY);
  digitalWrite(VOL_A, HIGH);
   delay(SIGNAL_DELAY);
}

void volUp()
{
  digitalWrite(VOL_A, LOW);
   delay(SIGNAL_DELAY);
  digitalWrite(VOL_A, HIGH);
  digitalWrite(VOL_B,   LOW);
  delay(SIGNAL_DELAY);
  digitalWrite(VOL_B, HIGH);
  delay(SIGNAL_DELAY);
}
   
void setupBlueToothConnection()
{
  blueToothSerial.begin(9600); //using   the default baud rate of HC-06
  blueToothSerial.print("AT+NAMEdupa1"); //set   the name - in fact it would be enough to do it just once, also a reset is needed   after the change

  delay(2000); //a delay just to make sure that the setup   is completed
  blueToothSerial.flush();
}

Volume control program for the Attiny

arduino

A program that simulates the rotary encoder by sending appropriate volume up and down signal cycles and communicates with a Bluetooth module to receive "volume up" and "volume down" messages from it.

1//THIS IS FOR ATTINY85 ONLY!
2#include <SoftwareSerial.h>  //Software  Serial Port
3
4//vol cntrl pins
5#define VOL_A 0
6#define VOL_B 1
7
8//buttons  pin
9#define BTNS A1
10
11//bluetooth pins
12#define RxD 3
13#define TxD 4
14
15//bluetooth  connection
16SoftwareSerial blueToothSerial(RxD,TxD);
17
18//signal segment timing  (ms)
19#define SIGNAL_DELAY 80
20
21//it takes ~64 cycles to take the volume  from min to max
22
23void setup() {
24  //init buttons
25  pinMode(BTNS, INPUT);
26  
27  //init volume outputs
28  pinMode(VOL_A, OUTPUT);
29  pinMode(VOL_B, OUTPUT);
30  digitalWrite(VOL_A, HIGH);
31  digitalWrite(VOL_B, HIGH);
32
33  //init BT
34  pinMode(RxD, INPUT);
35  pinMode(TxD, OUTPUT);
36  setupBlueToothConnection();
37}
38
39void  loop() {
40  //read buttons state & send appropriate signals to the stereo
41  int btnState = analogRead(BTNS);
42  if(btnState < 300) {
43    volDown();
44  } else {
45    if(btnState < 700) {
46      volUp();
47    }
48  }
49
50  //read remote commands over BT & send appropriate signals to the stereo
51  char  recvChar;
52  while (blueToothSerial.available() > 0 ) {
53    recvChar = blueToothSerial.read();
54    if (recvChar == '1') {
55      volUp();
56    } else {
57      if (recvChar  == '2') {
58        volDown();
59      }
60    }
61  }
62}
63
64void volDown()
65{
66  digitalWrite(VOL_B, LOW);
67  delay(SIGNAL_DELAY);
68  digitalWrite(VOL_B, HIGH);
69  digitalWrite(VOL_A, LOW);
70  delay(SIGNAL_DELAY);
71  digitalWrite(VOL_A, HIGH);
72  delay(SIGNAL_DELAY);
73}
74
75void volUp()
76{
77  digitalWrite(VOL_A, LOW);
78  delay(SIGNAL_DELAY);
79  digitalWrite(VOL_A, HIGH);
80  digitalWrite(VOL_B,  LOW);
81  delay(SIGNAL_DELAY);
82  digitalWrite(VOL_B, HIGH);
83  delay(SIGNAL_DELAY);
84}
85  
86void setupBlueToothConnection()
87{
88  blueToothSerial.begin(9600); //using  the default baud rate of HC-06
89  blueToothSerial.print("AT+NAMEdupa1"); //set  the name - in fact it would be enough to do it just once, also a reset is needed  after the change
90
91  delay(2000); //a delay just to make sure that the setup  is completed
92  blueToothSerial.flush();
93}
94

//THIS IS FOR ATTINY85 ONLY!
#include <SoftwareSerial.h>  //Software  Serial Port

//vol cntrl pins
#define VOL_A 0
#define VOL_B 1

//buttons  pin
#define BTNS A1

//bluetooth pins
#define RxD 3
#define TxD 4

//bluetooth  connection
SoftwareSerial blueToothSerial(RxD,TxD);

//signal segment timing  (ms)
#define SIGNAL_DELAY 80

//it takes ~64 cycles to take the volume  from min to max

void setup() {
  //init buttons
  pinMode(BTNS, INPUT);
  
  //init volume outputs
  pinMode(VOL_A, OUTPUT);
  pinMode(VOL_B, OUTPUT);
  digitalWrite(VOL_A, HIGH);
  digitalWrite(VOL_B, HIGH);

  //init BT
  pinMode(RxD, INPUT);
  pinMode(TxD, OUTPUT);
  setupBlueToothConnection();
}

void  loop() {
  //read buttons state & send appropriate signals to the stereo
  int btnState = analogRead(BTNS);
  if(btnState < 300) {
    volDown();
  } else {
    if(btnState < 700) {
      volUp();
    }
  }

  //read remote commands over BT & send appropriate signals to the stereo
  char  recvChar;
  while (blueToothSerial.available() > 0 ) {
    recvChar = blueToothSerial.read();
    if (recvChar == '1') {
      volUp();
    } else {
      if (recvChar  == '2') {
        volDown();
      }
    }
  }
}

void volDown()
{
  digitalWrite(VOL_B, LOW);
  delay(SIGNAL_DELAY);
  digitalWrite(VOL_B, HIGH);
  digitalWrite(VOL_A, LOW);
  delay(SIGNAL_DELAY);
  digitalWrite(VOL_A, HIGH);
  delay(SIGNAL_DELAY);
}

void volUp()
{
  digitalWrite(VOL_A, LOW);
  delay(SIGNAL_DELAY);
  digitalWrite(VOL_A, HIGH);
  digitalWrite(VOL_B,  LOW);
  delay(SIGNAL_DELAY);
  digitalWrite(VOL_B, HIGH);
  delay(SIGNAL_DELAY);
}
  
void setupBlueToothConnection()
{
  blueToothSerial.begin(9600); //using  the default baud rate of HC-06
  blueToothSerial.print("AT+NAMEdupa1"); //set  the name - in fact it would be enough to do it just once, also a reset is needed  after the change

  delay(2000); //a delay just to make sure that the setup  is completed
  blueToothSerial.flush();
}

Downloadable files

A full variant of the volume control (with LEDs and Bluetooth)

Connect it to your stereo system's volume encoder A and B signals and 5V line + GND

A full variant of the volume control (with LEDs and Bluetooth)