Multiplexy

The aim of this post is to address a query by the user "Boli" (see the comments page of the post "Arduino MIDI out example"). This a little demonstration of how to read up to 16 analog devices into the Arduino via 2 4051 multiplexers using 2 analog input pins and 3 digital output pins (plus RX and TX pins for serial transmission).

It should be noted that i have breadboarded and tested this method.

Obviously, this is a "barebones" example - if one was to actually implement this, a good idea might be to at least incorporate some sort of request byte from the host computer for each packet of 16 bytes received from the Arduino.

In other words, the patch must be started and then the Arduino must be reset (along with the zl group object) in order to really circumvent the issue of which byte corresponds to channel 1 of the first multiplexer.

But hey, this is just a quick little demo, yeah? Additional features can be easily added to this example without too much strain.


Hardware
The following connections should be made:

4051 (1)

• pins 6, 7, 8 to GND
• pin 16 to 5V
• pin 3 to Arduino analog input pin 0
• pin 11 to Arduino digital pin 2
• pin 10 to Arduino digital pin 3
• pin 9 to Arduino digital pin 4
• analog sensors 1- 8 (eg. pots, LDRs, etc etc) to pins 13, 14, 15, 12, 1, 5, 2, 4

4051 (2)

• pins 6, 7, 8 to GND
• pin 16 to 5V
• pin 3 to Arduino analog input pin 1
  
• pin 11 to Arduino digital pin 2
• pin 10 to Arduino digital pin 3
• pin 9 to Arduino digital pin 4
• analog sensors 9 - 16 (eg. pots, LDRs, etc etc) to pins 13, 14, 15, 12, 1, 5, 2, 4

Arduino Sketch:

byte data;

void setup() {

Serial.begin(57600);
DDRD = B00011110;

}

void loop() {
for(int i = 0; i < 16; i++) {

PORTD = (i % 8) << 2;

data = (analogRead(i / 8)) / 4;

Serial.print(data);
}
delay(5);

}

Max/MSP Patch:
Here you can see a most basic patch to receive the data.


Breadboard Picture:
Here you can see a breadboard example. Note that I have only connected one pot, because i only had one pot on hand at the time of writing this. But the idea remains the same.