AN4650 datasheet(30/102 Pages) STMICROELECTRONICS

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Reading output data

AN4650

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DocID027415 Rev 1

3.5

Understanding output data

The measured acceleration data are sent to the OUTX_H_XL, OUTX_L_XL, OUTY_H_XL,

OUTY_L_XL, OUTZ_H_XL, and OUTZ_L_XL registers. These registers contain,

respectively, the most significant part and the least significant part of the acceleration

signals acting on the X, Y, and Z axes.

The measured angular rate data are sent to the OUTX_H_G, OUTX_L_G, OUTY_H_G,

OUTY_L_G, OUTZ_H_G, and OUTZ_L_G registers. These registers contain, respectively,

the most significant part and the least significant part of the angular rate signals acting on

the X, Y, and Z axes.

The complete output data for the X, Y, Z channels is given by the concatenation

OUTX_H_XL(G) & OUTX_L_XL(G), OUTY_H_XL(G) & OUTY_L_XL(G) , OUTZ_H_XL(G)

& OUTZ_L_XL(G) and it is expressed as a two’s complement number.

Both acceleration data and angular rate data are represented as 16-bit numbers.

3.5.1

Big-little endian selection

The LSM6DS3 allows swapping the content of the lower and the upper part of the output

data registers (i.e. OUTX_H_XL(G) with OUTX_L_XL(G), and OUT_TEMP_H with

OUT_TEMP_L) in order to be compliant with both little-endian and big-endian data

representations.

“Little Endian” means that the low-order byte of the number is stored in memory at the

lowest address, and the high-order byte at the highest address. This mode corresponds to

the BLE bit of the CTRL3_C register set to 0 (default configuration).

On the contrary, “Big Endian” means that the high-order byte of the number is stored in

memory at the lowest address, and the low-order byte at the highest address. This mode

corresponds to the BLE bit of the CTRL3_C register set to 1.

3.5.2

Example of output data

Table 18 provides a few basic examples of the accelerometer data that is read in the data

registers when the device is subject to a given acceleration.

Table 19 provides a few basic examples of the gyroscope data that is read in the data

registers when the device is subject to a given angular rate.

The values listed in the following tables are given under the hypothesis of perfect device

calibration (i.e. no offset, no gain error,....) and practically show the effect of the BLE bit.

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