Software

AN4450

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DocID025978 Rev 1

6

Software

A detailed register list is reported in the LPS25H datasheet. In This section we collect useful

information on how to handle possible exceptions on the communication bus and how to

properly use the information coming from the device.

6.1

Hints

1.

would be to send 9 stop bits (which will flush the bus). This is usually done by SW using

SDA is high prior to generating a START bit.

2.

The serial bus power consumption can be reduced by reducing the data traffic:

–

Using built-in HW averaging instead of SW averaging

–

Reduce the polling rate when waiting for the one-shot measurement completion

(Section 4.3)

–

The INT1 pin can be used as event to minimize serial bus polling

6.2

One-shot mode conversion time estimation

Typical conversion time



ex: Tavg = 64; Pavg = 512; Typ. conversation time

ODT=25 Hz)



ex: Tavg = 32; Pavg = 128; Typ. conversation time



The formula is accurate within +/- 3% at room temperature

6.3

Reference SW to get started with LPS25H

There are some examples of C source files that provide the baseline in initializing,

configuring and performing measurements with the pressure sensor.

6.4

Pressure to altitude conversion

The simplest and widely used barometer (altitude) formula used in most watches comes

from the US Standard Atmosphere, for example the 1976 edition.

Example of the source code is shown below:

void From_Pressure_mb_To_Altitude_US_Std_Atmosphere_1976_ft(double*

Pressure_mb, double* Altitude_ft) {

//=(1-(Pressure/1013.25)^0.190284)*145366.45

*Altitude_ft = (1-pow(*Pressure_mb/1013.25,0.190284))*145366.45;

}

void From_ft_To_m(double* ft, double* m) {