Data Sheet
Final Datasheet
BME280 Environmental sensor
Page 30
BST-BME280-DS001-10 | Revision 1.1 | May 2015 Bosch Sensortec
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Note: Specifications within this document are subject to change without notice.
6. Digital interfaces
The BME280 supports the I²C and SPI digital interfaces; it acts as a slave for both protocols.
The I²C interface supports the Standard, Fast and High Speed modes. The SPI interface
011) in 4-
wire and 3-wire configuration.
The following transactions are supported:
Single byte write
multiple byte write (using pairs of register addresses and register data)
single byte read
multiple byte read (using a single register address which is auto-incremented)
6.1 Interface selection
Interface selection is done automatically based on CSB (chip select) status. If CSB is connected
to V
DDIO
, the I²C interface is active. If CSB is pulled down, the SPI interface is activated. After
CSB has been pulled down once (regardless of whether any clock cycle occurred), the I²C
interface is disabled until the next power-on-reset. This is done in order to avoid inadvertently
decoding SPI traffic to another slave as I²C data. Since the device startup is deferred until both
V
DD
and V
DDIO
are established, there is no risk of incorrect protocol detection because of the
power-up sequence used. However, if I²C is to be used and CSB is not directly connected to
V
DDIO
but is instead connected to a programmable pin, it must be ensured that this pin already
outputs the V
DDIO
level during power-on-reset of the device. If this is not the case, the device will
be locked in SPI mode and not respond to I²C commands.
6.2 I²C Interface
The I²C slave interface is compatible with Philips I²C Specification version 2.1. For detailed
timings, please review Table 33. All modes (standard, fast, high speed) are supported. SDA and
SCL are not pure open-drain. Both pads contain ESD protection diodes to VDDIO and GND. As
the devices does not perform clock stretching, the SCL structure is a high-Z input without drain
capability.
Figure 8: SDI/SCK ESD drawing