A PROBLEM with I2C (two slaves) : two ADXL345 and a mega2560

Hello,
As we know the same hardwares have the same address in I2C.
So I come up with a method to connect two ADXL345.
I use a CD4053 analog switch. In every loop, I connect the PIN_SCL in the board to one of the SCL in the two hardwares. So I make sure that I can get the data1 to control servo1, and data2 to control servo2.
Well, I don't know why, after running for about 30s, it locks.
I change the delay from 200ms to 1000ms, it can running about 1min, and the same.

So I'm puzzled now. I guess the configuration of mega2560 is too low to run my complex code?

Thank you very very much!

code :
#include <Servo.h>

boolean x=false;

Servo servo1,servo2;

#define CD4053_C 10
#define CD4053_B 9
#define CD4053_A 8

//PIN
#define PIN_SDA 20
#define PIN_SCL 21

//I2C (sparkfun breakout)
#define Register_ID 0
#define Register_2D 0x2D
#define Register_X0 0x32
#define Register_X1 0x33
#define Register_Y0 0x34
#define Register_Y1 0x35
#define Register_Z0 0x36
#define Register_Z1 0x37

#include <Wire.h>
int ADXAddress = 0x53; // the default 7-bit slave address
int reading = 0;
int val=0;
int X0,X1,X_out;
int Y0,Y1,Y_out;
int Z1,Z0,Z_out;
double Xg,Yg,Zg;

int pos1,pos2;
char flag=1;

void Wire_Start(){
Wire.beginTransmission(ADXAddress);
Wire.write(Register_2D);
Wire.write(8); //measuring enable
Wire.endTransmission(); // stop transmitting
}

void Wire_Get(){
//--------------X
Wire.beginTransmission(ADXAddress); // transmit to device
Wire.write(Register_X0);
Wire.write(Register_X1);
Wire.endTransmission();
Wire.requestFrom(ADXAddress,2);
if(Wire.available()<=2)
{
X0 = Wire.read();
X1 = Wire.read();
X1=X1<<8;
X_out=X0+X1;
}
//------------------Y
Wire.beginTransmission(ADXAddress); // transmit to device
Wire.write(Register_Y0);
Wire.write(Register_Y1);
Wire.endTransmission();
Wire.requestFrom(ADXAddress,2);
if(Wire.available()<=2)
{
Y0 = Wire.read();
Y1 = Wire.read();
Y1=Y1<<8;
Y_out=Y0+Y1;
}
//------------------Z
Wire.beginTransmission(ADXAddress); // transmit to device
Wire.write(Register_Z0);
Wire.write(Register_Z1);
Wire.endTransmission();
Wire.requestFrom(ADXAddress,2);
if(Wire.available()<=2)
{
Z0 = Wire.read();
Z1 = Wire.read();
Z1=Z1<<8;
Z_out=Z0+Z1;
}
//----------------
Xg=X_out/256.0;
Yg=Y_out/256.0;
Zg=Z_out/256.0;
}

void setup()
{
Wire.begin();
if(x)
Serial.begin(9600);
delay(100);

pinMode(CD4053_A,OUTPUT);
pinMode(CD4053_B,OUTPUT);
pinMode(CD4053_C,OUTPUT);
// enable to measute g data

servo2.write(175);
servo2.attach(47);

servo1.write(175);
servo1.attach(49);

pos1=servo1.read();
pos2=servo2.read();
if(x){
Serial.print("-->Start: pos1:");
Serial.print(pos1);
Serial.print(" pos2:");
Serial.println(pos2);}
digitalWrite(CD4053_A,HIGH);
digitalWrite(CD4053_B,LOW);
digitalWrite(CD4053_C,LOW);
delay(100);
Wire_Start();
digitalWrite(CD4053_A,LOW);
digitalWrite(CD4053_B,HIGH);
delay(100);
Wire_Start();

}

void loop()
{
if(x){
Serial.print("----");
Serial.print((flag+0));
Serial.println("----");}
switch(flag){
case 1: {
pos1=servo1.read();
if(x)
Serial.println(pos1);
digitalWrite(CD4053_A,HIGH);
digitalWrite(CD4053_B,LOW);
// digitalWrite(CD4053_C,LOW);
Wire_Get();
if(Xg>0)
pos1=90+(Xg<1?85Xg:85);
else
pos1=90+(Xg>-1?85Xg:-85);
servo1.write(pos1);
flag=2;
break;
}
case 2:{
pos2=servo2.read();
if(x)
Serial.println(pos2);
digitalWrite(CD4053_B,HIGH);
digitalWrite(CD4053_A,LOW);
// digitalWrite(CD4053_C,LOW);
Wire_Get();
if(Xg>0)
pos2=90+(Xg<1?85Xg:85);
else
pos2=90+(Xg>-1?85Xg:-85);
servo2.write(pos2);
flag=1;
break;
}
}
if(x){
Serial.print("X= ");
Serial.print(Xg);
Serial.print(" ");
Serial.print("Y= ");
Serial.print(Yg);
Serial.print(" ");
Serial.print("Z= ");
Serial.println(Zg);}
delay(1000);
}

Waitting ...

I don't think that is the correct multiplexer for an I2C bus. The multiplexer must be either open collector or bidirectional.

Do a Google search for I2C multiplexer.

I2C mux example

Thanks for your answers!

I know it's not the correct multiplexer. While I can't change the address of my hardwares, so it's the only way to achieve it. And it seems no problem theoretically.

er..nobody

And it seems no problem theoretically.

With that IC, it is a problem theoretically. You need an IC that has open collector or tri-state outputs. The CD4053 is neither.

SurferTim:
With that IC, it is a problem theoretically. You need an IC that has open collector or tri-state outputs. The CD4053 is neither.

I just use the CD4053 to connect the SCL between ADXL345 and the board. SCL is One-way transmission, so why can't i use it?

Thanks again!

If just the clock line, you may be able to get away with it. I haven't tried it with just the SCK line multiplexed like that. Does it work for you?

I get it. I just didn't connect the VEE of the CD4053 to GND.
Now everything is OK.

So maybe I have found a new way to connect two even more slaves to the I2C bus, even though they have the same address.

Thanks all above!!!