Using two TCA9548As to control 16 adafruit aht20 sensors

Qwiic System
1

I am very new to Arduino and need a bit of help as I am out of my depth.

Using an UNO, I am trying to read 16 identical Adafruit AHT20 sensors using two SparkFun Qwiic Mux Breakouts (TCA9548A) and get temp and humidity readings from each. I have added the required solder to one of the boards so that the addresses of the Mux boards should be 0x70 and 0x71

I am able to get 8 sensors working well off one Mux board buy using library examples but when I try and add the second board, the data behaves erratically, eg jumping around a bit and dropping down to 0 when the humidity gets high.

The mux boards are in a bus from the UNO, with a sensor attached to each available port.

The code I am trying to use is below. Apologies for untidiness.

#include <Wire.h>

#include <SparkFun_I2C_Mux_Arduino_Library.h>
QWIICMUX myMux;

#define NUMBER_OF_SENSORS_BOARD_1 8
#define NUMBER_OF_SENSORS_BOARD_2 8

#include <Adafruit_AHTX0.h>

Adafruit_AHTX0 aht;

unsigned long myTime;

void setup() {
  Serial.begin(115200);
  Serial.println("Multiple Muxes with Many Sensors");

  Wire.begin();

  //Initialise mux boards
 
  if (myMux.begin(0x70) == false)
  {
    Serial.println("Mux 0x70 not detected. Freezing...");
    while (1)
      ;
  }
  Serial.println("Mux 0x70 detected");


  bool initSuccess = true;

  for (byte x = 0; x < NUMBER_OF_SENSORS_BOARD_1; x++)
  {
    myMux.setPort(x);
    if (! aht.begin()) {
      Serial.print("Sensor ");
      Serial.print(x);
      Serial.println(" on board 1 did not begin! Check wiring");
      initSuccess = false;
    }
    else
    {
      //Configure each sensor
      Serial.print("Sensor ");
      Serial.print(x);
      Serial.println(" on 0x70 found!");
    }
  }

  if (initSuccess == false)
  {
    Serial.print("Freezing...");
    while (1)
      ;
  }

  Serial.println("Mux Shield 0x70 online");
 
 
  //Initialise mux boards
 

  if (myMux.begin(0x71) == false)
  {
    Serial.println("Mux 0x71 not detected. Freezing...");
    while (1)
     ;
  }
  Serial.println("Mux 0x71 detected");




  for (byte x = 0; x < NUMBER_OF_SENSORS_BOARD_2; x++)
  {
    myMux.setPort(x);
    if (! aht.begin()) {
      Serial.print("Sensor ");
      Serial.print(x);
      Serial.println(" on board 2 did not begin! Check wiring");
      initSuccess = false;
    }
    else
    {
      //Configure each sensor
      Serial.print("Sensor ");
      Serial.print(x);
      Serial.println(" on 0x71 found!");
    }
  }

  if (initSuccess == false)
  {
    Serial.print("Freezing...");
    while (1)
      ;
  }

  Serial.println("Mux Shield 0x71 online");

}

void loop() {

  myTime = millis();
  Serial.print(myTime);

  myMux.begin(0x70);
 
  for (byte x = 0; x < NUMBER_OF_SENSORS_BOARD_1; x++){
    myMux.setPort(x);

    sensors_event_t humidity, temp;
    aht.getEvent(&humidity, &temp);
   
    Serial.print(",");
    Serial.print(temp.temperature);
    Serial.print(",");
    Serial.print(humidity.relative_humidity);

    delay(50);

 
  }

 
  myMux.begin(0x71);
 
  for (byte x = 0; x < NUMBER_OF_SENSORS_BOARD_2; x++){
    myMux.setPort(x);

    sensors_event_t humidity, temp;
    aht.getEvent(&humidity, &temp);
   
    Serial.print(",");
    Serial.print(temp.temperature);
    Serial.print(",");
    Serial.print(humidity.relative_humidity);

    delay(50);

 
  }

 
  Serial.println();
  delay(480);
}

any help would be appreciated.

Thanks

2

I’d guess that the pull-up resistance is adding up to too much/too little…not sure if the adafruit sensors have pull-ups, you might have to add a few/remove a few