Communication lost between Sparkfun MUX and 8 displays

Qwiic System
1

I am using Arduino UNO with a Qwiic Shield so I could use Qwiic connectors. I connected one Mux (TCA9548A) to the shield. My 8 Qwiic Alphanumeric Displays ((VK16K33) are then connected the MUX.

I am trying to write down a value on each one of the displays, but following problem has happened so far:

  1. When all 8 displays are connected, not a single display showed anything.

  2. When 4 displays are connected, It worked for almost 3 minutes and then it frizzed.

  3. When 3 displays are connected, it works fine.

I cut down the display pull up resistors, but nothing changed.

I added separate power supplies for each of the displays, but it didn’t help.

I checked the connections, but it was fine as well.

It seems something wrong with I2C communication, in which when I increase the number of displays it cannot keep up with the communication.

I will appreciated if you could help me with this problem.

Thank you all in advance.

Here it is my code:

#include <Wire.h>
#include <SparkFun_Alphanumeric_Display.h>
#include <SparkFun_I2C_Mux_Arduino_Library.h> 

HT16K33 display;
QWIICMUX myMux;

String dis;
int long p = 1;

void setup() {
  Serial.begin(9600);  
  Wire.begin();
  myMux.begin(0x72);
  if (myMux.begin(0x72) == false)
  {
    Serial.println("Mux not detected. Freezing...");
    while (1) ;
  }

  for (int x = 0 ; x < 8 ; x++)
  { 
    myMux.setPort(x);
    display.begin();
    if (display.begin() == false)
      {
        Serial.println("Device did not acknowledge! Freezing.");
        while(1);
      }   
    myMux.disablePort(x);
  }
}

void loop() {

  for (byte x = 0 ; x < 8 ; x++)
  { 
    dis = p;
    myMux.setPort(x);
    display.print(dis); 
    myMux.disablePort(x);
    delay(10);
    p = p+1;
  }  
  delay(10);  
}
2

The problem may or may not be in your code. Is your power supply sufficient for 8 displays? I fear that the power supply cannot give sufficient current to all 8 displays.

3

Thank you for your reply.

Yes, the power supply is sufficient.

4

To make sure about about power supply, now I used an external power supply from DC power supply device and it solved the problem. Previously I was using Arduino pins but it didn’t work. In the display data sheet it says that the required current is 2 mA, but my experiment shows that it actually is 0.2 A.

5

It looks like you are only creating one instance of display. That class stores some local data, so you would need a separate instance of it for each display. Look at https://forum.sparkfun.com/viewtopic.ph … nt#p220782 for an example of using an array of instances for each mux channel.

/mike

6

Thank you so much.