AN4506 Просмотр технического описания (PDF) - STMicroelectronics

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AN4506

L3GD20H: 3-axis digital output gyroscope

STMicroelectronics 

AN4506

Reading angular rate data

3.5.3

Edge-sensitive trigger (LVLen = 0; EXTRen = 1; IMPen = 0)

Once enabled, the gyroscope output registers are updated with the next generated X, Y, Z

gyroscope data at the rising edge of the DEN input signal. If no rising edge occurs, the

gyroscope output registers are not updated.

When the ODR selected is 800 Hz, the maximum DEN sample frequency is

fDEN = 1/TDEN = 400 Hz.

Figure 6. Data synchronization: edge sensitive

3.6

3.6.1

3.6.2

Understanding angular rate data

The measured angular rate data are sent to the OUT_X_H, OUT_X_L, OUT_Y_H,

OUT_Y_L, OUT_Z_H, and OUT_Z_L 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 angular rate data for the X (Y, Z) channel is given by the concatenation

OUT_X_H & OUT_X_L (OUT_Y_H & OUT_Y_L, OUT_Z_H & OUT_Z_L) and it is

expressed as a 2’s complement number.

Data alignment

Angular rate data are represented as 16-bit numbers and are left-justified.

Big-little endian selection

The L3GD20H allows the content of the lower and the upper part of the angular rate

registers to be swapped (i.e. OUT_X_H with OUT_X_L), 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 the memory at the

lowest address, and the high-order byte at the highest address. (The little end comes first.)

This mode corresponds to bit BLE (in CTRL4 register) reset to 0 (default configuration).

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

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

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