General description

UM1477

14/22

Doc ID 022373 Rev 1

4.4

Motor position feedback

The MCU must provide the signals to direct the motor rotation and it then requires a means

of determining the rotor's orientation/position (relative to the stator coils).

Some designs use Hall effect sensors or a rotary encoder to directly measure the rotor's

position. Others measure the back EMF in the undriven phase to gather the rotor position,

eliminating the need for separate Hall effect sensors; this method is called sensorless

control.

This board is able to manage both Hall effect sensor feedback and back EMF zero-crossing

feedback.

Sensored drive

The first method uses position sensors, usually Hall sensors, to measure the rotor position.

Sensorless drive

The other method is based on the BEMF. It analyzes the zero crossing of the floating phase

BEMF signal to establish the commutation point. The match between the BEMF signal of

the floating phase, with respect to the motor neutral point (or star point), is used to generate

the commutation between two consecutive steps in order to achieve rotor synchronization.

More information about the rotor position detection techniques implemented in the STM8

motor control firmware can be found in the UM0708 user manual.

4.5

STM8S105K4 microcontroller

The STM8S105xx access line 8-bit microcontrollers offer from 16 to 32 Kbytes Flash

program memory, plus integrated true data EEPROM. They are referred to as medium-

density devices in the STM8S microcontroller family reference manual (RM0016).

All devices of the STM8S105xx access line provide the following benefits:

●

Reduced system cost

–

Integrated true data EEPROM for up to 300 k write/erase cycles

–

High system integration level with internal clock oscillators, watchdog and

brownout reset.

●

Performance and robustness

–

16 MHz CPU clock frequency

–

Robust I/O, independent watchdogs with separate clock source

–

Clock security system.

●

Short development cycles

–

Application scalability across a common family product architecture with

compatible pinout, memory map and modular peripherals

–

Full documentation and a wide choice of development tools.

●

Product longevity

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Advanced core and peripherals made in a state-of-the-art technology

–

A family of products for applications with a 2.95 to 5.5 V operating supply.

Please refer to the STM8S105xx datasheet for an overview of the complete range of

peripherals proposed in this family.