AN4650 datasheet(28/102 Pages) STMICROELECTRONICS

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Reading output data

AN4650

28/102

DocID027415 Rev 1

Reading output data

3.1

Startup sequence

Once the device is powered up, it automatically downloads the calibration coefficients from

the embedded flash to the internal registers. When the boot procedure is completed, i.e.

after approximately 20 milliseconds, the accelerometer and gyroscope automatically enter

Power-Down mode.

To turn on the accelerometer and gather acceleration data, it is necessary to select one of

the operating modes through the CTRL1_XL register and to enable at least one of the axes

through CTRL9_XL.

The following general-purpose sequence can be used to configure the accelerometer:

To turn on the gyroscope and gather angular rate data, it is necessary to select one of the

operating modes through the CTRL2_G register and to enable at least one of the axes

through CTRL10_C.

The following general-purpose sequence can be used to configure the gyroscope:

3.2

Using the status register

The device is provided with a STATUS_REG register which should be polled to check when

a new set of data is available. The XLDA bit is set to 1 when a new set of data is available at

accelerometer output; the GDA bit is set to 1 when a new set of data is available at

gyroscope output.

For the accelerometer (the gyroscope is similar), the reads should be performed as follows:

Write CTRL9_XL = 38h

// Acc X, Y, Z axes enabled

Write CTRL1_XL = 60h

// Acc = 416Hz (High-Performance mode)

Write INT1_CTRL = 01h

// Acc Data Ready interrupt on INT1

Write CTRL10_C = 38h

// Gyro X, Y, Z axes enabled

Write CTRL2_G = 60h

// Gyro = 416Hz (High-Performance mode)

Write INT1_CTRL = 02h

// Gyro Data Ready interrupt on INT1

Read STATUS

If XLDA = 0, then go to 1

Read OUTX_L_XL

Read OUTX_H_XL

Read OUTY_L_XL

Read OUTY_H_XL

Read OUTZ_L_XL

Read OUTZ_H_XL

Data processing

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