4051 multiplexer - problem

Forum 2005-2010 (read only) Hardware Interfacing
1

Hello!
I'm trying to build digital preamp using 3 TDA7314s.
For now I'm developing it with Arduino.
It also has encoder and LCD.
As Arduino has only 1 hardware i2c I decided to go with multiplexer CD4051.

My problem is that if I connect SDA line to one of the TDA7314s - it works perfectly. For now I just want to adjust volume.

But now I want to adjust volume on all chips, so I used multiplexer. It kinda works but it skips commands. For example - if I adjust volume from 20 to lets say 50 it stays the same for a while, and then suddenly jumps to the level of encoder, i.e. it skips or disturbs i2c transmissions.

I did a simple test - on pressing the button it should mute all channels. And it works approximately 2 times in 10.

Here is my code:

#include <Wire.h>
#include <LiquidCrystal.h>

int lcdRS = 3;
int lcdEn = 4;
int lcdD4 = 9;
int lcdD5 = 10;
int lcdD6 = 11;
int lcdD7 = 12;

int encoder0PinA = 6;
int encoder0PinB = 7;
int encoder0PinButton = 5;

int S0Pin = 16; //analog 0
int S1Pin = 15; //analog 1
int S2Pin = 14; //analog 2

int val; 
int encoder0Pos = 0;
int encoder0PinALast = LOW;
int n = LOW;
int pressButtonLast = HIGH;

LiquidCrystal lcd(lcdRS, lcdEn, lcdD4, lcdD5, lcdD6, lcdD7);

int what = 0; // what are we doing 0 = volume

int  bin [] = {000, 1, 10}; //for outputs 1, 2 and 3

void send_i2c(int);
void set_volume(void);
void select_output(int);

void setup() {
  lcd.begin(16, 4);
  lcd.print("hello, world!");

  pinMode (encoder0PinA,INPUT);
  pinMode (encoder0PinB,INPUT);
  
  pinMode(S0Pin, OUTPUT);    // s0
  pinMode(S1Pin, OUTPUT);    // s1
  pinMode(S2Pin, OUTPUT);    // s2

  Serial.begin (9600); //for debug
  Wire.begin();
//read saved volume settings and send through wire
for (int i = 0; i <= 2; i++){
  
  select_output(i); //we are doing it for each SDA
  Wire.beginTransmission(B1000000); //TDA7314s address
//  Wire.send(B00000000);    //  set volume to max
  Wire.send(B10100000);  //set attenuation on right
  Wire.send(B10000000);  //set attenuation on left
  Wire.send(B01011100); //select input 
  Wire.endTransmission();    // stop transmitting
  }
  
}

void loop() {
   n = digitalRead(encoder0PinA);
   if ((encoder0PinALast == LOW) && (n == HIGH)) {
     if (digitalRead(encoder0PinB) == LOW) {
       encoder0Pos--;
     } else {
       encoder0Pos++;
     }

switch(what){
case 0:
for (int i = 0; i <= 2; i++){
  select_output(i);
  set_volume();
}
break;
default: 
for (int i = 0; i <= 2; i++){
  select_output(i);
  set_volume();
}
break;
}

     Serial.print (encoder0Pos);
     Serial.print ("/");  
    lcd.setCursor(0, 1);
lcd.print(encoder0Pos); 
   } 

   if(digitalRead(encoder0PinButton) == LOW && pressButtonLast == HIGH){
     Serial.print ("press/");
pressButtonLast = LOW;     
   }else{
if(digitalRead(encoder0PinButton) == HIGH)
      pressButtonLast = HIGH;
   }
   
   encoder0PinALast = n;

}

void set_volume(void){
if(encoder0Pos > 63)
  encoder0Pos = 63;
if(encoder0Pos < 0)
  encoder0Pos = 0;
send_i2c(63 - encoder0Pos);
  }

void send_i2c(int data){
  Wire.beginTransmission(B1000000); //44?
  Wire.send(data);
  Wire.endTransmission();    // stop transmitting
}

void select_output(int output){

  int row = bin[output];      
  int r0 = row & 0x01;
  int r1 = (row>>1) & 0x01;
  int r2 = (row>>2) & 0x01;
 
  digitalWrite(S0Pin, r0);
  digitalWrite(S1Pin, r1);
  digitalWrite(S2Pin, r2);
}

I will be grateful for any input.

Leonti