You could also try powering the sensor modules with 5V to their Vin pins. The 3.3V pin on a Nano is very weak and can only supply a small current. It could be that these modules need a larger current. But continue to power the multiplexer with 3.3V from the Nano.
Did any of your modules arrive with the PCB header pins not soldered on? If so, did you solder them, and make a neat job? Simply pushing the PCB header pins through the module's holes is very unlikely to work, and dry solder joints, shorts etc could be another reason.
I made changes to your original code. I put a row of '*' before the changes I made. I did not remove the code for the multiplexer but you should do that.
One sensor is on the hardware I2C pins and the other is on digital pins 5 and 6.
I don't have the sensors so I can't test the code.
#include <Wire.h>
#include "DFRobot_ENS160.h"
#include "Adafruit_AHTX0.h"
//************************************************
SoftI2C SoftWire = SoftI2C(5, 6); //SDA, SCL
// Create ENS160 and AHT21 instances for two channels
DFRobot_ENS160_I2C ens160_1(&Wire, 0x53);
//************************************************
DFRobot_ENS160_I2C ens160_2(&SoftWire, 0x53);
Adafruit_AHTX0 aht_1;
Adafruit_AHTX0 aht_2;
// Multiplexer address
#define TCA_ADDR 0x70
// Function to select a multiplexer channel (0–7)
void tcaSelect(uint8_t channel) {
if (channel > 7) return;
Wire.beginTransmission(TCA_ADDR);
Wire.write(1 << channel);
Wire.endTransmission();
}
void setup() {
Serial.begin(115200);
Wire.begin();
Serial.println("Initializing sensors via TCA9548A...");
// --- Channel 0: Sensor Module 1 ---
tcaSelect(0);
if (!aht_1.begin()) {
Serial.println("AHT21 #1 not found! Check wiring on channel 0.");
while (1) delay(10);
}
while (ens160_1.begin() != NO_ERR) {
Serial.println("Waiting for ENS160 #1...");
delay(3000);
}
ens160_1.setPWRMode(ENS160_STANDARD_MODE);
// --- Channel 1: Sensor Module 2 ---
tcaSelect(1);
//************************************************
if (!aht_2.begin(&SoftWire, 1, 0x38)) {
Serial.println("AHT21 #2 not found! Check wiring on channel 1.");
while (1) delay(10);
}
while (ens160_2.begin() != NO_ERR) {
Serial.println("Waiting for ENS160 #2...");
delay(3000);
}
ens160_2.setPWRMode(ENS160_STANDARD_MODE);
Serial.println("Both sensor sets ready. Warming up...");
delay(60000); // 60-second warm-up
}
void loop() {
sensors_event_t humidity1, temp1, humidity2, temp2;
// --- Channel 0: Module 1 ---
tcaSelect(0);
aht_1.getEvent(&humidity1, &temp1);
ens160_1.setTempAndHum(temp1.temperature, humidity1.relative_humidity);
Serial.println("=== Sensor Module 1 (TCA Ch. 0) ===");
printSensorData(ens160_1, temp1.temperature, humidity1.relative_humidity);
// --- Channel 1: Module 2 ---
tcaSelect(1);
aht_2.getEvent(&humidity2, &temp2);
ens160_2.setTempAndHum(temp2.temperature, humidity2.relative_humidity);
Serial.println("=== Sensor Module 2 (TCA Ch. 1) ===");
printSensorData(ens160_2, temp2.temperature, humidity2.relative_humidity);
Serial.println("==================================");
delay(5000);
}
// Helper function to print one module's data
void printSensorData(DFRobot_ENS160_I2C &ens, float temp, float hum) {
uint8_t status = ens.getENS160Status();
if (status == 0 || status == 1 || status == 2) {
Serial.print("eCO2: "); Serial.print(ens.getECO2()); Serial.println(" ppm");
Serial.print("TVOC: "); Serial.print(ens.getTVOC()); Serial.println(" ppb");
Serial.print("AQI: "); Serial.println(ens.getAQI());
}
Serial.print("Temp: "); Serial.print(temp); Serial.println(" °C");
Serial.print("Hum: "); Serial.print(hum); Serial.println(" %");
Serial.println("---");
}
/*
Connection Description
Uno/Nano SDA (A4) → TCA9548A SDA Shared data line
Uno/Nano SCL (A5) → TCA9548A SCL Shared clock line
TCA9548A VCC → 5V (or 3.3V), GND → GND Power
Channel 0 (SDA0/SCL0) → ENS160 #1 + AHT21 #1 First module
Channel 1 (SDA1/SCL1) → ENS160 #2 + AHT21 #2 Second module
Both ENS160 and AHT21 on each channel use the same addresses (0x53 and 0x38), but the TCA9548A isolates them.
*/
