bmp280 datasheet

Bosch
Sensortec | BMP280 Data sheet
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48
Modifications reserved | Data subject to change without notice
Document number: BST-BMP280-DS001-23 Revision_1.23_11202
0
GND
V
DDIO
output driver (only for SDI)
SDI /SCL
high-z level shifter
GND
Figure 6: SDI/SCK ESD drawing
The 7-bit device address is 111011x. The 6 MSB bits are fixed. The last bit is changeable by SDO
value and can be changed during operation. Connecting SDO to GND results in slave address
1110110 (0x76); connection it to V
DDIO
results in slave address 1110111 (0x77), which is the same 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)
• SDO: Slave address LSB (GND = ‘0’, V
DDIO
= ‘1’)
CSB must be connected to V
DDIO
to select I²C interface. SDI is bi-directional with open drain to GND: it
must be externally connected to V
DDIO
via a pull up resistor. Refer to chapter 6 for 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)