Hello,

I try to build a battery powered temperature sensor but I only found one sensor who works with low power under 2 volt. This is the bmp280 from bosch. But in i2c mode he need a power from 0,6mA so my battery life are only 2 month. Now the library from adafruit runs the sensor in normal mode and so I insert two new functions in the library:

void Adafruit_BMP280::sleep() {
write8(BMP280_REGISTER_CONTROL, 0x3C);
}

void Adafruit_BMP280::wakeup() {
write8(BMP280_REGISTER_CONTROL, 0x3F);
}

The first one write 00 to the first bits in the data register - the sleep mode.
The wakeup function rewrite the first bits with 11 - the normal mode.

void loop() {
...
...

Temp = bmp.readTemperature();
Press = bmp.readPressure() / 100.0;
Altit = bmp.readAltitude(1013.25);

bmp.sleep();

sleep(30000);

bmp.wakeup();
}

Now the sketch needs only 0,2µA in the sleep mode - it is much more better than 0,6mA.

Best regards

Elmar