BMP085

Data sheet

Bosch Sensortec

Rev. 1.2

Page 17

15 October 2009

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as copying and passing on to third parties. BOSCH and the symbol are registered trademarks of Robert Bosch GmbH, Germany.

Specifications are subject to change without notice.

Timing diagram for starting pressure measurement

ACKS

S

ACKS

Module address

write 0xEE

Register address

0xF4

Control register

data 0xF4

SCL

SDA

ACKS

P

4.4 Start temperature and pressure measurement

The timing diagrams to start the measurement of the temperature value UT and pressure value

UP are shown below. After start condition the master sends the device address write, the

register address and the control register data. The BMP085 sends an acknowledgement

(ACKS) every 8 data bits when data is received. The master sends a stop condition after the

last ACKS.

Abbreviations:

S

Start

P

Stop

ACKS

Acknowledge by Slave

ACKM

Acknowledge by Master

NACKM

Not Acknowledge by Master

Control registers values for different internal oversampling_setting (osrs):

Instead of waiting for the maximum conversion time, the output pin EOC (end of conversion)

can be used to check if the conversion is finished (logic 1) or still running (logic 0). After the

conversion is finished BMP085 switches automatically in standby mode.

Measurement

Control register value

(register address 0xF4)

Max. conversion time

[ms]

Temperature

0x2E

4.5

Pressure

(osrs = 0)

0x34

4.5

Pressure

(osrs = 1)

0x74

7.5

Pressure

(osrs = 2)

0xB4

13.5

Pressure

(osrs = 3)

0xF4

25.5