AN2281 datasheet(32/38 Pages) STMICROELECTRONICS

32 / 38 page

List of software functions and interrupt service routines

AN2281

32/38

Get_Rotor_Freq

Freq_computing

Input:

Target speed in u16 format. Data returned by Get_Target_Speed function

can be directly used as input data

Returns:

None

Caution:

The function is compiled only if closed loop driving mode is defined.

Duration:

The PI routine average execution time is strongly dependent on the error

between actual and target speed. In worst-case conditions (high error), the

routine duration is equal to 157 µsec.

See also::

Section 5.2.4

Description:

This function computes the stator frequency to be applied to the motor. At

start-up, the function returns the stator frequency initialization value. As

soon as the first valid Hall sensor semi-period measurement has been

performed and until the fourth semi-period measurement has been

completed, the function returns the last measured rotor frequency. After the

fourth semi-period measurement has been carried out, the average rotor

frequency (based on last 4 measurements) is returned.

Input:

None

Returns:

Stator frequency with 0.1192Hz resolution.

Duration:

222 µsec in steady state

Description:

This function is called by Get_Rotor_Freq function, it performs the division

for converting the Hall sensor signal semi-period measurements into a

frequency (0x3FFFF/period).

Input:

Hall sensor semi-period (u16 format with 16µsec resolution).

Returns:

Electrical frequency, defined by the formula:

Electrical frequency = Rotor speed (in rpm)* Number of Pole pairs/60

with 0.1192Hz resolution.

Duration:

204 µsec.

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