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Multiplying Multiplexers In Arduino

About the project

Multiplexing Arduino Inputs: 16 Analogue Sensors on 2 Analogue Pins! Full video and written tutorial on how to read a full 16 potentiometers from only 2 analogue pins!

Project info

Difficulty: Moderate

Platforms: Arduino

Estimated time: 1 hour

License: GNU General Public License, version 3 or later (GPL3+)

Items used in this project

Hardware components

	Arduino (any - I used uno)	x 1
	Potentiometers (or whatever sensor you would like to read)	x 16
	CD4051BE Multiplexing Chips	x 2

Software apps and online services

Arduino

Story

This is a follow on from my last post

Using a single multiplexer chip on the Arduino to create eight inputs takes up five pins – four digital, and one analogue. Other than ‘converting’ the digital pins to analogue, this doesn’t seem particularly impressive in terms of pin efficiency. However, the benefits of multiplexing become more apparent as you add extra multiplexers to the circuit.

Adding a second CD4051B chip is very similar to adding the first. The main point of interest here is that you can use the same digital pins on the Arduino to send the binary messages to the multiplexer. This starts to make multiplexing very pin efficient, as each chip only requires a single analogue pin to transmit information over.

You can have as many multiplexers as you have available analogue pins, meaning an Arduino Uno with six analogue pins can read 48 analogue inputs. With a bit of thought, you could add multiplexers to each input pin of the first multiplexer – but this would involve changing the code around significantly. One of the main disadvantages of using multiplexers is the waiting time between each read – installing a multiplexer through another multiplexer necessitates longer wait times, as each pin on the first chip needs to be read multiple times before moving on.

Video Explanation

The Code

Because there are now 16 independent inputs coming into the serial monitor, it becomes increasingly difficult to read. I plan to use these numbers in a Max patch, so I mainly need to get the text into a format that is easily read by Max.

I figured out that the best way to do this was to send all of the numbers as a list, without naming them, with spaces between each integer (this, honestly, makes the serial monitor look clearer too). Max can read the list as 16 distinct numbers, and an unjoin object can be used to separate this into the 16 potentiometer values. I will go into more detail on the max patch in my next blog post.

References:

Gammon, N., 2013. Microprocessors: 74HC4051 Multiplexer/Demultiplexer. [online] Gammon.com.au. Available at: http://www.gammon.com.au/forum/?id=11976 [Accessed 25 November 2020].

Code

The Arduino Code (16 Sensors)

int wait = 10;
 const int A_Pots = A0;
 const int B_Pots = A1;
 const int Inhibit_Mux = 7;
 void setup() 
 {
   Serial.begin(9600);
   pinMode(Inhibit_Mux,OUTPUT);
   digitalWrite(Inhibit_Mux,LOW);
   DDRB = 0b00000111;  //PORT 8,9,10 as output
   PORTB = 0b00000000; //PORT 8,9,10 set to low
   pinMode(A_Pots,INPUT);
   pinMode(B_Pots,INPUT);
 }
 void loop() 
 {
   PORTB=0b00000000; //Data flow - X0
   int Step1A = analogRead(A_Pots); //read data from X0 A_Pots
   Serial.print(Step1A);
   int Step1B = analogRead(B_Pots); //read data from X0 B_Pots
   Serial.print(" ");
   Serial.print(Step1B);
   delay(wait);
 PORTB=0b00000001;  //Data flow - X1
   int Step2A = analogRead(A_Pots); //read data from X1 A_Pots
   Serial.print(" ");
   Serial.print(Step2A);
   int Step2B = analogRead(B_Pots); //read data from X1 B_Pots
   Serial.print(" ");
   Serial.print(Step2B);
   delay(wait);
 PORTB=0b00000010;  //Data flow - X2
   int Step3A = analogRead(A_Pots); //read data from X2 A_Pots
   Serial.print(" ");
   Serial.print(Step3A);
   int Step3B = analogRead(B_Pots); //read data from X2 B_Pots
   Serial.print(" ");
   Serial.print(Step3B);
   delay(wait);
 PORTB=0b00000011;  //Data flow - X3
   int Step4A = analogRead(A_Pots); //read data from X3 A_Pots
   Serial.print(" ");
   Serial.print(Step4A);
   int Step4B = analogRead(B_Pots); //read data from X3 B_Pots
   Serial.print(" ");
   Serial.print(Step4B);
   delay(wait);
 PORTB=0b00000100;  //Data flow - X4
   int Step5A = analogRead(A_Pots); //read data from X4 A_Pots
   Serial.print(" ");
   Serial.print(Step5A);
   int Step5B = analogRead(B_Pots); //read data from X4 B_Pots
   Serial.print(" ");
   Serial.print(Step5B);
   delay(wait);
 PORTB=0b00000101;  //Data flow - X5
   int Step6A = analogRead(A_Pots); //read data from X5 A_Pots
   Serial.print(" ");
   Serial.print(Step6A);
   int Step6B = analogRead(B_Pots); //read data from X5 B_Pots
   Serial.print(" ");
   Serial.print(Step6B);
   delay(wait);
 PORTB=0b00000110;  //Data flow - X6
   int Step7A = analogRead(A_Pots); //read data from X7 A_Pots
   Serial.print(" ");
   Serial.print(Step7A);
   int Step7B = analogRead(B_Pots); //read data from X7 B_Pots
   Serial.print(" ");
   Serial.print(Step7B);
   delay(wait);
 PORTB=0b00000111;  //Data flow - X7
   int Step8A = analogRead(A_Pots); //read data from X8 A_Pots
   Serial.print(" ");
   Serial.print(Step8A);
   int Step8B = analogRead(B_Pots); //read data from X8 B_Pots
   Serial.print(" ");
   Serial.println(Step8B);
   delay(wait);
 digitalWrite(Inhibit_Mux,HIGH);  // Inhibit / stop all data
   delay(wait);  
   digitalWrite(Inhibit_Mux,LOW);  // Inhibit /  let data flow
 }

Credits

CharisCat

Musician, video producer, and general tinkerer from Devon in the UK.

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Multiplying Multiplexers In Arduino

About the project

Project info