AN2388 datasheet(32/54 Pages) STMICROELECTRONICS

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Software design

AN2388

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Software design

4.1

Introduction

This section describes the software design of the AC induction vector control drive

application. In particular, the software organization is outlined as well as the utilization of

different variables and the handling of the DSP-based micro functions used in this

application in order to speed-up the execution time. A short explanation on numerical

considerations is also provided inherent within fixed-point calculation.

4.2

Software organization

The software is organized in two different modules: the initialization module and the run

module. The first is performed only once at the beginning. The second module consists of a

“Waiting Loop” of Interrupt event. The interrupt (PWM ISR) is served every PWM Timer

underflow. The complete FOC algorithm is computed within the PWM ISR and thus runs at

the same frequency as the chopping frequency chosen to drive the power devices.

An overview of the software is given in the flow chart below:

Figure 29.

Main organization flow chart

The micro peripheral PWM Unit is used to generate the necessary pulsed signal to the

power electronics board. It is programmed to generate symmetrical PWM signals at a

frequency of 16kHz (@64MHz, 15.6ns of resolution).

The following figure illustrates the time diagram for the initialization and the operating.

Start

µC Initialization

(Peripherals)

Software

Initialization

Waiting

Loop

PWM ISR

Loop

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