UM0324 datasheet(22/105 Pages) STMICROELECTRONICS

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Getting started with the library

UM0324

22/105

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#define TIMER0_HANDLES_TACHO

To be uncommented if tachogenerator-based speed measurement is performed by

TIMER0.

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#define TIMER1_HANDLES_TACHO

To be uncommented if tachogenerator-based speed measurement is performed by

TIMER1.

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#define TIMER2_HANDLES_TACHO

To be uncommented if tachogenerator-based speed measurement is performed by

TIMER2. (Default; required if using STR750-MCKIT, in conjunction with Input Capture 1

choice - see below).

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#define TACHO_INPUT_TI1

To be uncommented if sensor output signal is wired to TimerX Input Capture 1. (Default

- in conjunction with TIMER2 choice; required if using STR750-MCKIT).

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#define TACHO_INPUT_TI2

To be uncommented if sensor output signal is wired to TimerX Input Capture 2.

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#define MAX_SPEED_FDBK

This parameter defines the frequency above which speed feedback is not realistic in

the application: this allows to discriminate glitches for example. The unit is 0.1Hz. By

default, it is set to 6400 (640.0Hz), which corresponds to approximately 20000 RPM for

a two pole pair motor.

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#define MAX_SPEED

This parameter is the value returned by the function TAC_GetRotorFreqInHz if

measured speed is greater than MAX_SPEED_FDBK. The default value is 640Hz, but

it can be 0 or FFFF depending on how this value is managed by the upper layer

software.

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#define MAX_PSEUDO_SPEED

This parameter is the value returned by the function TAC_GetRotorFreq if measured

speed is greater than MAX_SPEED_FDBK. The unit is rad/pwm period

π rad = 0xFFFF). See Section 4.7.4: Converting Hertz into pseudo frequency on

page 83 for more details.

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#define MIN_SPEED_FDBK

This parameter is the frequency below which speed feedback is not realistic in the

application: this allows to discriminate too low frequency. This value is set to 1 Hz by

default, and depends on sensor and signal conditioning stage characteristics. Typically,

the tacho signal is too weak at very low speed to trigger input capture on the MCU.

Note:

The MC_tacho_prm.h file includes two formulas that allow to compute the minimum sensed

speed when speed is increasing (during start-up) or decreasing (during motor stop).

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#define MAX_RATIO

Maximum possible TIMER clock prescaler ratio:

–

This defines the lowest speed that can be measured (when counter = 0xFFFF).

–

It also prevents the clock prescaler from decreasing excessively when the motor is

stopped. (This prescaler is automatically adjusted during each and every capture

interrupt to optimize the timing resolution).

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#define MAX_OVERFLOWS

This is the maximum number of consecutive timer overflows taken into account. It is set

by default to 10: if the timer overflows more than 10 times (meaning that the tacho

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