Tailor-made solution with A4941 and STM32F091RC for exceptional BLDC motor control
Unleash the force of brushless
Published Feb 26, 2024
Click board™
Brushless 5 Click
Dev Board
Nucleo-64 with STM32F091RC MCU
Compiler
NECTO Studio
MCU
STM32F091RC
Experience smoother and quieter operation with our brushless motor control system, enhancing user comfort and reducing noise in various applications
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Hardware Overview
How does it work?
Brushless 5 Click is based on the A4941, a three-phase sensorless fan driver from Allegro MicroSystems. This IC features a proprietary sensorless BEMF zero-crossing sensing technique, which provides a speed reading via the FG output pin, routed to the INT pin of the mikroBUS™. The BEMF zero-crossing is the point where the voltage of the undriven motor winding (BEMF is short for Back Electromotive Force) crosses the motor center tap (neutral point) voltage. Neutral point voltage can be approximated using an internally generated reference voltage when the used motor does not provide one. BEMF zero-crossing occurs when a pole of the rotor is aligned with a pole of the stator and is used as a positional reference for the commutation controller section of the A4941. When the zero-crossing occurs, an internal signal is set to a HIGH state, while the beginning of the next phase commutation sets this signal to a LOW state. The signal is latched between the states so that commutation transients do not affect it. This provides a robust and accurate position-sensing system. The internal sequencer is used to commutate the phases based on the position feedback. During the startup period, the internal
oscillator provides the phase commutation instead until a valid BEMF positional signal sequence is detected. The current through the coils is maximum at this stage since the PWM signal with a 100% duty cycle is applied during a startup sequence. The Lock Detect feature prevents the motor from locking up or falling out of synchronization while protecting the coils and the IC from overheating. If a valid FG signal is not detected for 2 seconds, the outputs are turned off for 5 seconds. After this time-out, another restart is attempted. An internal peak overcurrent protection is set to about 1A. If the motor drains more than 1A, especially during the startup, the overcurrent protection will be activated, turning off the output stage for about 25µs. This can prevent the startup of some types of motors, so the longest startup delay of 200ms is chosen for this Click board™. The PWM pin is routed to the same pin of the mikroBUS™ and can be used to control the current through the coils. When the HIGH logic level is applied to the PWM input pin, the current from the power supply flows through the coils. No current is running through the coils when the LOW logic level is applied to the PWM
input pin. Applying a PWM signal with a frequency of 15 kHz to 30 kHz will result in a coil current corresponding to the applied PWM's duty cycle. The minimum pulse width is fixed at 6 μs, allowing the minimum speed to be maintained, even when applying PWM signals with a very low duty cycle. Applying a LOW logic level to the PWM pin for more than 500µs will put the device in low power consumption (standby) mode. The power supply for the motor coils is connected via the external two-pole terminal. VBAT+ input is connected to the positive voltage, while the GND input is connected to the power supply's ground. The voltage of the external power supply should stay between 5V and 16V. The most common use is with 12V motors. The BLDC motor coils should be connected to the four-pole output screw terminal. Respective motor phases are connected to the A, B, and C terminal outputs, while the central point of the BLDC motor can be connected to the output labeled as N. IF the used BLDC motor does not have the central (neutral) point output, the neutral point needed for the BEMF sensing will be generated internally.
Features overview
Development board
Nucleo-64 with STM32F091RC MCU offers a cost-effective and adaptable platform for developers to explore new ideas and prototype their designs. This board harnesses the versatility of the STM32 microcontroller, enabling users to select the optimal balance of performance and power consumption for their projects. It accommodates the STM32 microcontroller in the LQFP64 package and includes essential components such as a user LED, which doubles as an ARDUINO® signal, alongside user and reset push-buttons, and a 32.768kHz crystal oscillator for precise timing operations. Designed with expansion and flexibility in mind, the Nucleo-64 board features an ARDUINO® Uno V3 expansion connector and ST morpho extension pin
headers, granting complete access to the STM32's I/Os for comprehensive project integration. Power supply options are adaptable, supporting ST-LINK USB VBUS or external power sources, ensuring adaptability in various development environments. The board also has an on-board ST-LINK debugger/programmer with USB re-enumeration capability, simplifying the programming and debugging process. Moreover, the board is designed to simplify advanced development with its external SMPS for efficient Vcore logic supply, support for USB Device full speed or USB SNK/UFP full speed, and built-in cryptographic features, enhancing both the power efficiency and security of projects. Additional connectivity is
provided through dedicated connectors for external SMPS experimentation, a USB connector for the ST-LINK, and a MIPI® debug connector, expanding the possibilities for hardware interfacing and experimentation. Developers will find extensive support through comprehensive free software libraries and examples, courtesy of the STM32Cube MCU Package. This, combined with compatibility with a wide array of Integrated Development Environments (IDEs), including IAR Embedded Workbench®, MDK-ARM, and STM32CubeIDE, ensures a smooth and efficient development experience, allowing users to fully leverage the capabilities of the Nucleo-64 board in their projects.
Microcontroller Overview
MCU Card / MCU
Architecture
ARM Cortex-M0
MCU Memory (KB)
256
Silicon Vendor
STMicroelectronics
Pin count
64
RAM (Bytes)
32768
You complete me!
Accessories
Click Shield for Nucleo-64 comes equipped with two proprietary mikroBUS™ sockets, allowing all the Click board™ devices to be interfaced with the STM32 Nucleo-64 board with no effort. This way, Mikroe allows its users to add any functionality from our ever-growing range of Click boards™, such as WiFi, GSM, GPS, Bluetooth, ZigBee, environmental sensors, LEDs, speech recognition, motor control, movement sensors, and many more. More than 1537 Click boards™, which can be stacked and integrated, are at your disposal. The STM32 Nucleo-64 boards are based on the microcontrollers in 64-pin packages, a 32-bit MCU with an ARM Cortex M4 processor operating at 84MHz, 512Kb Flash, and 96KB SRAM, divided into two regions where the top section represents the ST-Link/V2 debugger and programmer while the bottom section of the board is an actual development board. These boards are controlled and powered conveniently through a USB connection to program and efficiently debug the Nucleo-64 board out of the box, with an additional USB cable connected to the USB mini port on the board. Most of the STM32 microcontroller pins are brought to the IO pins on the left and right edge of the board, which are then connected to two existing mikroBUS™ sockets. This Click Shield also has several switches that perform functions such as selecting the logic levels of analog signals on mikroBUS™ sockets and selecting logic voltage levels of the mikroBUS™ sockets themselves. Besides, the user is offered the possibility of using any Click board™ with the help of existing bidirectional level-shifting voltage translators, regardless of whether the Click board™ operates at a 3.3V or 5V logic voltage level. Once you connect the STM32 Nucleo-64 board with our Click Shield for Nucleo-64, you can access hundreds of Click boards™, working with 3.3V or 5V logic voltage levels.
Brushless DC (BLDC) Motor with a Hall sensor represents a high-performance motor from the 42BLF motor series. This motor, wired in a star configuration, boasts a Hall Effect angle of 120°, ensuring precise and reliable performance. With a compact motor length of 47mm and a lightweight design tipping the scales at just 0.29kg, this BLDC motor is engineered to meet your needs. Operating flawlessly at a voltage rating of 24VDC and a speed range of 4000 ± 10% RPM, this motor offers consistent and dependable power. It excels in a normal operational temperature range from -20 to +50°C, maintaining efficiency with a rated current of 1.9A. Also, this product seamlessly integrates with all Brushless Click boards™ and those that require BLDC motors with Hall sensors.
Used MCU Pins
mikroBUS™ mapper
Take a closer look
Schematic
Step by step
Project assembly
Start by selecting your development board and Click board™. Begin with the Nucleo-64 with STM32F091RC MCU as your development board.
Track your results in real time
Application Output via Debug Mode
1. Once the code example is loaded, pressing the "DEBUG" button initiates the build process, programs it on the created setup, and enters Debug mode.
2. After the programming is completed, a header with buttons for various actions within the IDE becomes visible. Clicking the green "PLAY" button starts reading the results achieved with the Click board™. The achieved results are displayed in the Application Output tab.
Software Support
Library Description
This library contains API for Brushless 5 Click driver.
Key functions:
brushless5_set_duty_cycle- Generic sets PWM duty cyclebrushless5_pwm_stop- Stop PWM modulebrushless5_pwm_start- Start PWM module
Open Source
Code example
This example can be found in NECTO Studio. Feel free to download the code, or you can copy the code below.
/*!
* @file
* @brief Brushless5 Click example
*
* # Description
* This library contains an API for the Brushless5 Click driver.
* This example showcases how to initialize and use the Brushless 5 click.
* The click has a brushless 5 motor driver which controls the work
* of the motor through the BLDC terminal.
* In order for this example to work a motor and a power supply are needed.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initializes the GPIO driver and configures the PWM peripheral for
* controlling the speed of the motor.
*
* ## Application Task
* This is an example that demonstrates the use of a Brushless 5 Click board.
* Brushless 5 Click communicates with the register via the PWM interface.
* Increases and decreasing the speed of the motor demonstrate speed control.
* Results are being sent to the Usart Terminal where you can track their changes.
*
* @author Nikola Peric
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "brushless5.h"
// ------------------------------------------------------------------ VARIABLES
static brushless5_t brushless5;
static log_t logger;
// ------------------------------------------------------ APPLICATION FUNCTIONS
void application_init ( void )
{
log_cfg_t log_cfg;
brushless5_cfg_t cfg;
/**
* Logger initialization.
* Default baud rate: 115200
* Default log level: LOG_LEVEL_DEBUG
* @note If USB_UART_RX and USB_UART_TX
* are defined as HAL_PIN_NC, you will
* need to define them manually for log to work.
* See @b LOG_MAP_USB_UART macro definition for detailed explanation.
*/
LOG_MAP_USB_UART( log_cfg );
log_init( &logger, &log_cfg );
log_info( &logger, "---- Application Init ----" );
Delay_ms( 100 );
// Click initialization.
brushless5_cfg_setup( &cfg );
BRUSHLESS5_MAP_MIKROBUS( cfg, MIKROBUS_1 );
brushless5_init( &brushless5, &cfg );
Delay_ms( 100 );
brushless5_set_duty_cycle ( &brushless5, 0.0 );
brushless5_pwm_start( &brushless5 );
log_info( &logger, "---- Application Task ----" );
Delay_ms( 1000 );
}
void application_task ( void )
{
static int8_t duty_cnt = 1;
static int8_t duty_inc = 1;
float duty = duty_cnt / 10.0;
brushless5_set_duty_cycle ( &brushless5, duty );
log_printf( &logger, "Duty: %d%%\r\n", ( uint16_t )( duty_cnt * 10 ) );
Delay_ms( 500 );
if ( 10 == duty_cnt )
{
duty_inc = -1;
log_printf( &logger, " Slowing down... \r\n" );
}
else if ( 0 == duty_cnt )
{
duty_inc = 1;
log_printf( &logger, " Increasing the motor speed... \r\n" );
}
duty_cnt += duty_inc;
Delay_ms( 500 );
}
void main ( void )
{
application_init( );
for ( ; ; )
{
application_task( );
}
}
// ------------------------------------------------------------------------ END
