Looking to kickstart a battery-powered BLDC motor control design? Look no further.

The STEVAL-PTOOL1V is one of two industrial-grade development boards from STMicroelectronics designed for use in low-voltage, brushless power tools. Based on the STSPIN32F0B that can be used to control 3-phase motors and optimized for single-shunt current implementations, the board comes pre-configured for both sensorless and sensored field-oriented control (FOC), and can be configured for plug-and-play six-step sensorless control thanks to onboard back electromagnetic field (BEMF) sensing circuitry.

Zooming in, the onboard STSPIN32F0B motor controller is a system-in-package (SiP) based on the STM32F0 microcontroller, a 3-phase half-bridge gate driver, a shunt resistor, 3.3V and 12V regulators, and an op-amp for current sensing and power-stage protection. In fact, the integrated  resistor connects to the op-amp to provide a degree of signal conditioning circuit, and an on-chip comparator can be used to provide overcurrent detection features.

Zooming out, the STEVAL-PTOOL1V supports a motor voltage rating of 7V to 45V and is powered by 2S to 6S Li-ion battery packs. It features a standby power consumption of less than 1 µA, but is still capable of delivering up to 15 A of continuous current. The power stage features an STripFET F7 60V N-channel Power MOSFET.

With an onboard embedded heatsink and protection mechanisms that include thermal shutdown, reverse biasing of power stage outputs, undervoltage lockout, overcurrent protection, and programmable thresholds, the STEVAL-PTOOL1V board measures in at a compact 70 mm x 30 mm footprint ideal for handhelds and a range of battery-powered applications.

The STEVAL-PTOOL1V1 In Action

From a development standpoint, the STEVAL-PTOOL1V’s plug-and-play six-step sensorless control is afforded by an input connector that accepts Hall effect sensors and an encoder. Position feedback from the Hall effect sensor is then incorporated into the free STSW-PTOOL1V1 six-step firmware provided with the kit, which provides a sample implementation of how to drive a BLDC motor called “voltage mode” that uses a trapezoidal driving technique and speed loop with a constant PWM duty cycle.

The STSW-PTOOL1V1 uses a timer to generate PWM phases that provides a current reference and drives signals, and comes with a pre-set GPIO, PWM, and IRQ configuration. The firmware can manage parameters such as min/max speed and direction, as well as speed control if an optional potentiometer is implemented on the STEVAL-PTOOL1V

As far as sensing, the STEVAL-PTOOL1V  is equipped with a shunt resistor that is mounted on the reference board to sense the current that is flowing into the motor phases. An external trimmer connected to the J9 connector also allows prototypers to deliver an analog signal directly to the aforementioned firmware as a setpoint on the speed control loop.

Programming and debugging is achieved through the SWD interface and a direct firmware update (DFU) feature that is administered via UART. As part of the STM32Cube ecosystem, developers can use the STM32CubeIDE, Keil Microcontroller Development Kit (MDK-ARM-STR), and IAR Embedded Workbench for Arm as development environments.

Getting Started with the STEVAL-PTOOL1V1

When getting started with the reference design board from STMicroelectronics it is important to first make sure you’re utilizing a Windows PC with either Windows 7, 8, or 10. From a hardware standpoint, the ST-LINK debugger/programmer and the STSW-PTOOL1V1 firmware are also required.

As previously mentioned, the board requires a power supply output voltage rating between 7V and 45V and a three-phase brushless motor with the same current and voltage ratings as the power supply. Next, fire up one of the IDEs listed above and download the user’s manual.

Then:

1. Check the mounting options according to the desired operation mode (see Section 2.1 Operation mode and sensing topology selection)
2. Connect an external trigger switch to J8 (the board offers the option of connecting an external trimmer to J9 to vary the motor speed)
3. Connect the brushless motor phases to J4, J5, and J6
4. Download the pre-compiled code through the SWD interface
5. Supply the board through J1 (positive) and J2 (ground)
6. Start developing your application using the STSW-PTOOL1V1 firmware example package as starting point

The STEVAL-PTOOL1V reference board can be ordered directly through the STMicroelectronics’s website for $40.43 for volumes between 1 to 500 units. For more information, visit www.st.com or check out the references below.

References:

• STEVAL-PTOOL1V1 Product Description: https://www.st.com/en/evaluation-tools/steval-ptool1v1.html?ecmp=tt9470_gl_link_feb2019&rt=um&id=UM2770#overview
• STEVAL-PTOOL1V1 User Manual: https://www.st.com/resource/en/user_manual/dm00732176-getting-started-with-the-stevalptool1v1-compact-reference-design-for-low-voltage-brushless-power-tools-based-on-stspin32f0b-stmicroelectronics.pdf
• STEVAL-PTOOL1V1 Data Brief: https://www.st.com/resource/en/data_brief/steval-ptool1v1.pdf