LPS27HHTW datasheet(11/55 Pages) STMICROELECTRONICS

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4.5

Interpreting pressure readings

The pressure data are stored in 3 registers: PRESS_OUT_H (2Ah), PRESS_OUT_L (29h), and PRESS_OUT_XL

(28h). The value is expressed as a 24-bit signed number (in 2’s complement).

To obtain the pressure in hPa, take the complete 24-bit word and then divide by the sensitivity 4096 LSB/

hPa. This same interpretation is applied to pressure readings when FIFO is enabled and the pressure

data are stored in 3 registers: FIFO_DATA_OUT_PRESS_XL (78h), FIFO_DATA_OUT_PRESS_L (79h), and

FIFO_DATA_OUT_PRESS_H (7Ah).

Figure 7. Pressure readings

PressureValue LSB =PRESS_OUT_H 2Aℎ &PRESS_OUT_L 29ℎ &PRESS_OUT_XL

28ℎ =3FF58Dℎ=4191629LSB signeddecimal

(1)

Pressure ℎPa =PressureValue LSB

Sensitivity = 4191629LSB

4096LSB/ℎPA=1023ℎPa

(2)

4.6

Interpreting temperature readings

The temperature data are stored in 2 registers: TEMP_OUT_H (2Ch) and TEMP_OUT_L (2Bh).

The value is expressed as 2’s complement. To obtain the temperature in °C, take the two’s complement

of the complete 16-bit word and then divide by the sensitivity 100 LSB/°C. This same interpretation is

applied to temperature readings when FIFO is enabled and the temperature data are stored in 2 registers:

FIFO_DATA_OUT_TEMP_H (7Ch) and FIFO_DATA_OUT_TEMP_L (7Bh).

Figure 8. Temperature readings

0 0 0 0 1 0 0 1

1 1 0 0 0 1 0 0

TEMP_OUT_H

TEMP_OUT_L

Temperature Value (LSB) = TEMP_OUT_H (2Ch) & TEMP_OUT_L (2Bh)

= 09C4 = 2500 LSB (decimal signed)

Temperature (°C) =

Temperature Value (LSB)

Sensitivity

2500 LSB

100 LSB/°C

= 25.00°C

LPS27HHTW

Interpreting pressure readings

DS13489 - Rev 1

page 11/55

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