74HC4067 Multiplexer with arduino uno

[hemnath]

Hi,

I am planning to get data from 16 channel multiplex(74HC4067) input into arduino uno.

I have connected I0 to I15 as +5V, on the serial monitor some of the pin values are showing as 0. Why is it 0 instead of 1?

// control pins output table in array form
// see truth table on page 2 of TI 74HC4067 data sheet
// connect 74HC4067 S0~S3 to Arduino D7~D4 respectively
// connect 74HC4067 pin 1 to Arduino A0
/*
byte controlPins[] = {B00000000, 
                  B10000000,
                  B01000000,
                  B11000000,
                  B00100000,
                  B10100000,
                  B01100000,
                  B11100000,
                  B00010000,
                  B10010000,
                  B01010000,
                  B11010000,
                  B00110000,
                  B10110000,
                  B01110000,
                  B11110000 }; 
                  */

byte controlPins[] = {B00000000, 
B00010000,
B00100000,
B00110000,
B01000000,
B01010000,
B01100000,
B01110000,
B10000000,
B10010000,
B10100000,
B10110000,
B11000000,
B11010000,
B11100000,
B11110000 }; 
 
// holds incoming values from 74HC4067                  
byte muxValues[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,};

int inPin = 8;     // pushbutton connected to digital pin 0
 
void setup()
{
  Serial.begin(9600);
  DDRD = B11111111; // set PORTD (digital 7~0) to outputs
    pinMode(inPin, INPUT);        // sets the digital pin as input
}
 
void setPin(int outputPin)
// function to select pin on 74HC4067
{

  PORTD = controlPins[outputPin];
}
 
void displayData()
// dumps captured data from array to serial monitor
{
  Serial.println();
  Serial.println("Values from multiplexer:");
  Serial.println("========================");
  for (int i = 0; i < 16; i++)
  {
    Serial.print("input I"); 
    Serial.print(i); 
    Serial.print(" = "); 
    Serial.println(muxValues[i]);
  }
  Serial.println("========================");  
}
 
void loop()
{
  for (int i = 0; i < 16; i++)
  {
    setPin(i); // choose an input pin on the 74HC4067
    muxValues[i]=digitalRead(inPin);
    delay(100);
  }
 
  // display captured data
  displayData();
  delay(2000); 
}

 

[KlausST]

Hi,

Show us your complete schematic. It may be hand drawn.

Please check: Don´t let any input pin floating. Not analog pins and not digital pins.

What about the "/E" connection of the HC4067.

Code:

  for (int i = 0; i < 16; i++)
  {
    setPin(i); // choose an input pin on the 74HC4067
    [COLOR="#FF0000"]delay(10);[/COLOR]    
    muxValues[i]=digitalRead(inPin);
    delay(90);
  }

Add the delay beween changing the MUX and performing a conversin for the analog value to settle.
Is the delay value in "milliseconds"?

I recommend to put a capacitor (at least 1nF) to each MUX input with connection to GND. And a 1M Ohms resistor in parallel to it to prevent the input from floating.
(C and R values depend on application)

If you want to connect any external circuitry to the analog inputs then don´t forget ESD protection and EMC filtering.

If you want to process AC signals, then you need anti aliasing filters, too.

Klaus