BlueberryE BreakoutBoard BME280

The BlueberryE BME280 is, as the name suggests, a breakout board for the Bosch BME280 humidity, pressure and temperature sensor. One unique feature is that it comes with a connector to the SeeedStudio Grove system. That way wiring etc becomes very simple and you do not need to fiddle around with breadboards etc. PLEASE NOTE the board is not 5V tolerant.

Key Info

sensor combisensor temperature pressure humididty

Interfaces

I2C SPI

In case you do not yet know the BME280. It measures in parallel humididty (± 3%) pressure (absolute accuracy ± 1hPa) and temperatur ( ± 1°C). As altitude depends on pressure you can use it to estimate altitudewith an accuracy of ±1 meter. You can connect the BME280 alternatively over SPI or I2C. Operating Voltage is between 1.2V und 3.6V, typically 1.8V to 3.3V. It is not 5V tolerant.

What makes it special?

Good question, see the enumeration and find your reason why you need it:

  • It is pretty small just 18x10mm.

  • It fits into Grove ecosystem for easy connection but also allows to be used with a breadboard.

  • The pin header comes unsoldered so you are free to connects cables etc.

  • It has no onboard levelshifter to 5V so be careful when connecting it.

  • At the end it is pretty cheap.

The BBE-BME280 supports all communication modes described in the Bosch Datasheet (I2C, SPI 3 and 4 pin). As the BME280 has just 4 pins beside Vcc, Gnd they are used for multiple functions.

Pinlayout and solder jumpers

The following pictures show the schematic of the BBE BME280 as well as the locations of the solder jumpers on the backside of the board.

BME280

Solder jumpers.

BME280

The 6 pins on the right side allow access either through I2C or SPI as documented in the datasheet. The BME280 chip has only 8pins, so several of them have more than one function, that is also the reason why the BBE BME280 has 5 solder jumpers.

JP2 in the schematic is the 6pin header, described above. If you look at the backside of the board GND is at the same side as the solder jumpers.

Factory settings of the solder jumpers can be seen from the table below (first line) called I2C default.

|                 | SJ1 | SJ2 | SJ3 | SJ4 | SJ5 |
|-----------------|-----|-----|-----|-----|-----|
|I2C (default)    |     |     |     |  A  |  B  |
|I2C              |  x  |     |  x  |  A  | A/B |
|4-wire SPI       |     |     |     |  B  |     |
|3-wire SPI       |     |     |     |  B  |     |  
|-----------------|-----|-----|-----|-----|-----|

The solder jumpers are explained in the next two sections in more detail.

Please Note Never close solder jumper SJ2 and at the same time set SJ5 to B, as in that case there would be a static current through R3 schematic.

I2C

I2C is the factory setting of the board. As SJ5 is connected to GND the default I2C adress is 0x76. You can change the address to 0x77 by cutting JP5 connection to B and instead connect it to A.

I2C needs pull-up resistors on the bus. Usually this resistors are already existing e.g. on the microcontroller board. If this is not the case in your particular situation you can enable pull-ups R2 and R4 by closing SJ1 and SJ3.

SPI

The BME280 supports both 3 and 4 Wire SPI. To move from I2C to SPI change SJ4 to B, that way the CS line is available on JP2. Open all other solder jumpers.

Grove Connector

Using the Grove connector you can connect the board through I2C as well as supply power and GND. All solder jumper settings as described under I2C apply.

Following lines show some code snippets related to BreakoutBoard BME280.

There are plenty of libraries on Github for the BME280 you can use them until we are done with our own software.

Please Note contrary to several other BME280 breakout boards this one uses I2C adress 0x76 instead of 0x77. Take care if you use libraries.

BBE BreakoutBoard BME280

Schematic BBE BME280