To read data from the BME280, we used the Adafruit Python BME280 library, which depends upon the Adafruit Python GPIO library. The BME280 is on address 0x77 of the I2C bus it seems that 0x77 is used by Adafruit and by Drotek for their breakout boards: We found also an unbranded/Chinese maker which uses the 0x76 address. Once connected and powered-up, the i2cdetect tool detects the following chips (the device at address 0圆8 marked as “UU” - in use by a driver - is the DS3231 RTC clock):Ġ0: -ġ0: -Ģ0: -ģ0: -Ĥ0: -ĥ0: -Ħ0: - UU. This one seems to accept only the 5.0 volt, we provided that voltage on the power pin. The provided documentation is not so clear there are breakouts with this chip which have an internal voltage regulator, so they can accept 3.3 V or 5.0 V. The sensor can be connected via the SPI or the I2C interface, we prefer the I2C one. We purchased an BME280 breakout made by Drotek on eBay for about 13 €. Remove the package fake-hwclock which store the current time at shutdown and restore it at bootstrap:ĭpkg -purge fake-hwclock BME280 Barometric Sensor Hwclock: The Hardware Clock registers contain values that are either invalid (e.g. In that case you will receive this error when reading the clock: WARNING: Beware of the sleep command above! It seems that kernel modules require some time to settle and to expose the RTC device properly! If you try to instantiate the device too early you will corrupt the clock registers. # Wait for the device to bring to life, then set system clock from RTC. sleep 3 echo ds1307 0圆8 > /sys /class /i2c-adapter /i2c- 1 /new_device # Instantiate a DS1307 Realtime Clock at address 0圆8 of the I2C bus. # = Real Time Clock = # Wait for kernel modules to settle (sleep 1 => FAIL, sleep 2 => OK). There is a method, somewhat deprecated, but which should works with every startup system: add the commands into /etc/rc.local: To instantiate the DS1307/DS3231 device (RTC) at address 0圆8 of the I2C bus, we need to execute a comand, choose the proper method upon your startup process (sysvinit, systemd, etc.).
It will add the following line in /boot/config.txt dtparam=i2c_arm=on
Use raspi-config, Advanced Options ⇒ I2C to enable automatic loading of I2C kernel modules. This will work on Raspbian based on Debian Jessie 8.
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