cubecell and IIC sensors powered by Vext issue

Testing on IIC sensor such as BME280/BMP280 and DH1750, and controlled by Vext, it seems there is a problem on IIC bus when power back the Vext.

The dirty solution is to add Wire.begin(); and Wire.end();

so my structure is like this:(power related in red, IIC in green, sensors in blue)

pinMode(Vext, OUTPUT);

digitalWrite(Vext, LOW);

delay(200);

Wire.begin();

if (!bme280.init()) {

Serial.println("bme280 error!");

}

delay(100);

temperature = bme280.getTemperature();

pressure = bme280.getPressure() / 100;

humidity = bme280.getHumidity();

if(lightMeter.begin()){

Serial.println(F("BH1750 inited"));

}

delay(100);// critical to get reading, but the first reading is always 0

float lux = lightMeter.readLightLevel(true);

Serial.print("Light: ");

Serial.print(lux);

Serial.println(" lx");

Wire.end();

digitalWrite(Vext, HIGH);// turn off the Vext

It still get me a strange behave on DH1750, no matter what delay I added(tested 5sec), the first reading after reset is always 0

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