Datasheet

BMP280 Digital Pressure Sensor

Page 29

BST-BMP280-DS001-19 | Revision 1.19 | January 2018

Bosch Sensortec

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Note: Specifications within this document are subject to change without notice. Not intended for publication.

as BMP180’s I²C address. The SDO pin cannot be left floating; if left floating, the I²C address will

be undefined.

The I²C interface uses the following pins:

 SCK: serial clock (SCL)

 SDI:

data (SDA)

connection instructions.

The following abbreviations will be used in the I²C protocol figures:

 S

Start

 P

Stop

 ACKS

Acknowledge by slave

 ACKM

Acknowledge by master

 NACKM

Not acknowledge by master

5.2.1 I²C write

Writing is done by sending the slave address in write mode (RW = ‘0’), resulting in slave address

111011X0 (‘X’ is determined by state of SDO pin. Then the master sends pairs of register

addresses and register data. The transaction is ended by a stop condition. This is depicted in

Figure 7.

Start

RW ACKS

ACKS

ACKS

1

1

1

0

1

1

X

0

1

0

1

0

0

0

0

0

bit7

bit6

bit5

bit4

bit3

bit2

bit1 bit0

…

ACKS

ACKS

Stop

…

1

0

1

0

0

0

0

1

bit7

bit6

bit5

bit4

bit3

bit2

bit1 bit0

Register data - address A0h

Register address (A0h)

Register address (A1h)

S

Slave Address

Control byte

Data byte

Control byte

Data byte

P

Register data - address A1h

Figure 7: I²C multiple byte write (not auto-incremented)

5.2.2 I²C read

To be able to read registers, first the register address must be sent in write mode (slave address

111011X0). Then either a stop or a repeated start condition must be generated. After this the

slave is addressed in read mode (RW = ‘1’) at address 111011X1, after which the slave sends

out data from auto-incremented register addresses until a NOACKM and stop condition occurs.

This is depicted in Figure 8, where two bytes are read from register 0xF6 and 0xF7.