Read SHT30 and SHT40 from ENVIII-HAT and ENVIV-UNIT at the same time

Ivanks

Is it possible to change the I2C address?

I'm really interested to use a M5StickC Plus2 with an Unit and Hat sensor without any other hardware to read temperature

Both sensors SHT30 and SHT40 uses the same address by default (0x44).

I saw in the datasheet of the components that we can change de I2C address dynamically, but I've tried without any success.

Also in the sht4x library has two address options

#define SHT40_I2C_ADDR_44 0x44
#define SHT40_I2C_ADDR_45 0x45

Is there a way to do that?

felmue

Hello @Ivanks

you are corrrect, SHT30 has an ADDR pin which allows to change the I2C address:

The address of the sensor can be changed dynamically during operation by switching the level on the ADDR pin.

However in the ENVIII hat the ADDR pin is connected to GND. See schematic here. This means In order to change the I2C address you'd need to modify your ENVIII on a hardware level.

In contrast, according to its datasheet, SHT40 doesn't have an ADDR pin - the I2C address is predefined and reflected in the part number (A -> 0x44, B -> 0x45)

Products Details
SHT40-AD1B base RH&T accur., 0x44 I2C addr.
SHT40-BD1B base RH&T accur., 0x45 I2C addr.

Thanks
Felix

robski

would using pahub be helpfull? to "hide" unit address behind hub address?

Ivanks

Nice, thank you guys for the considerations.

For now the solution that I've found is to establish a connection once per sensor and end communication.

I'm not sure if is a good practice with I2C communication, but is working for a simple using.
Of course it has a little more delay in the measurements.

  if (!sht3x.begin(&Wire1, SHT3X_I2C_ADDR, 0, 26, 400000U)) {
    Serial.println("Couldn't find SHT3X");
    while (1) delay(1);
  }
  if (sht3x.update()) {
    Serial.print("SHT30 - Temperatura: ");
    Serial.print(sht3x.cTemp);
    Serial.print(" - Umidade: ");
    Serial.println(sht3x.humidity);

    //DISPLAY
    StickCP2.Display.fillRect(110, 30, 100, 30, BLACK);
    StickCP2.Display.setCursor(5, 30);
    StickCP2.Display.setTextColor(BLUE);
    StickCP2.Display.printf("SHT30: %.1f", sht3x.cTemp);
  }

  Wire.end();
  delay(1000);

  if (!sht4x.begin(&Wire, SHT40_I2C_ADDR_44, 32, 33, 400000U)) {
    Serial.println("Couldn't find SHT4X");
    while (1) delay(1);
  }

  sht4x.setPrecision(SHT4X_HIGH_PRECISION);
  sht4x.setHeater(SHT4X_NO_HEATER);

  if (sht4x.update()) {
    Serial.print("SHT40 - Temperatura: ");
    Serial.print(sht4x.cTemp);
    Serial.print(" - Umidade: ");
    Serial.println(sht4x.humidity);

    //DISPLAY
    StickCP2.Display.fillRect(110, 60, 100, 30, BLACK);
    StickCP2.Display.setCursor(5, 60);
    StickCP2.Display.setTextColor(YELLOW);
    StickCP2.Display.printf("SHT40: %.1f", sht4x.cTemp);
  }
  Wire.end();
  delay(1000);

felmue

Hello @Ivanks

I think that is a perfectly valid solution. Thanks for sharing.

Thanks
Felix