STM32 Nucleo Pack FOC and 6-step motor control platform for 3-phase low voltage motor

3.1 System architecture

A generic motor control system can be basically schematized as the arrangement of three main blocks (see Figure 2):

• Control block: its main task is to accept user commands and configuration parameters to drive a motor. The P-NUCLEO-IHM001 is based on NUCLEO-F302R8 board that provides all digital signals to perform the proper motor driving control algorithm (for instance 6-step or FOC).
• Power block: the X-NUCLEO-IHM07M1 is based on 3-phase inverter topology. The core of the power block embedded on board is the driver STSPIN L6230, which contains all the necessary active power and analog components to perform a low voltage PMSM motor control.
• PMSM Motor: low voltage 3-phase brushless motor.

Figure 2. System architecture: A block diagram illustrating the motor control system architecture, comprising a Control block (NUCLEO-F302R8), a Power block (X-NUCLEO-IHM07M1 with L6230 driver), and a PMSM Motor.

3.2 Building and run the motor control Nucleo Pack

The P-NUCLEO-IHM001 is a complete hardware development platform (Power & Control block + Motor) for STM32 Nucleo ecosystem to evaluate a motor control solution for single motor.

For a regular board operating, follow the hardware configuration shown below:

3.3 Hardware settings

1. The X-NUCLEO-IHM07M1 must be stacked on a NUCLEO-F302R8 board through the ST morpho connector. There is only one position allowed for this connection, in particular the two buttons on NUCLEO-F302R8 board (blue B1 and black B2) must be kept out, as shown in Figure 3.

Figure 3. X-NUCLEO-IHM07M1 and NUCLEO-F302R8 assembled: A photograph showing the X-NUCLEO-IHM07M1 expansion board physically connected and stacked onto the NUCLEO-F302R8 board via the ST morpho connector. Key buttons (B1, B2) on the NUCLEO board are visible.

The interconnection between the X-NUCLEO-IHM07M1 with STM32 NUCLEO board has been designed for a full-compatibility with a lot of control board and no modification of solder bridges is required.

2. Connect the three motor wires U,V,W at J2 connector as shown in the Figure 4: Motor connection with X-NUCLEO-IHM07M1: it is mandatory to connect the white or yellow wire to OUT1, the black one to OUT2 and the red one to OUT3, to respect clockwise and counterclockwise motor rotation, according to the firmware implementation.

Figure 4. Motor connection with X-NUCLEO-IHM07M1: A close-up photograph of the J2 motor connector on the X-NUCLEO-IHM07M1 board. Three wires from a 3-phase motor are shown connected, with labels indicating the expected wire colors and their corresponding OUT terminals: Red wire to OUT3, Black wire to OUT2, and White or Yellow wire to OUT1.

3. Select the jumper configuration on the power board to choose the desired control algorithm (6-step or FOC) as described below:

• On NUCLEO-F302R8 board, check jumper setting: JP1 open, JP5 (PWR) on E5V side, JP6 (IDD) closed.
• On X-NUCLEO-IHM07M1 expansion board:
  • Check jumper settings: J9^(b) closed, JP3 closed
  • For 6-step control set jumper settings as: JP1 and JP2 open, J5&J6 on 1Sh side^(b)
  • For FOC control set jumper settings as: JP1 and JP2 closed, J5&J6 on 3Sh side

^(b) It is important that supply voltage is powered off before control mode changing.

4. Connect DC supply voltage on J1^(c) connector and power-on (up to 12 V DC for BR2804 motor included in the Pack, as shown in Figure 5: Power supply connection for X-NUCLEO-IHM07M1).

Figure 5. Power supply connection for X-NUCLEO-IHM07M1: A diagram illustrating the power supply connection to the X-NUCLEO-IHM07M1 board via the J1 connector. Two terminals are shown, labeled '+Vdc' and 'Gnd', with wires connected.

5. At power-on (or reset) led D11 on X-NUCLEO-IHM07M1 board starts to blink according to the control algorithm choice:

• 2 times for FOC mode control
• 4 times for 6-step mode control

After the confirmation of control algorithm selected, the system is ready to start.

6. Push the blue button on NUCLEO-F302R8 (B1) and the motor starts to spin.

7. Rotate the potentiometer on X-NUCLEO-IHM07M1 board in order to regulate the motor speed.

The Table 1 shows the jumper configuration on X-NUCLEO-IHM07M1 board (see also Figure 6: X-NUCLEO-IHM07M1 – top layer with silk-screen and Figure 7: X-NUCLEO-IHM07M1 connectors view). According to the jumpers selection, it is possible to choose the

⁽¹⁾ JP1 and JP2 selection between FOC or 6-step current sensing circuit. It must be both closed (FOC selection) or both open (6-step selection - default setting)

⁽²⁾ It is recommended to verify that power supply voltage is not higher than 12V dc, in order to avoid damaging on NUCLEO-F302R8 board. For further details on Nucleo settings refer to UM1724 available from ST web site www.st.com.

⁽³⁾ J5 and J6 must have both the same configuration. Both 1-2 for three shunt configuration. Both 2-3 for single shunt configuration. On the silkscreen the correct position for three and for single shunt is indicated. Also the default position is indicated.

The Table 2 shows the main connector on X-NUCLEO-IHM07M1 board.

The X-NUCLEO-IHM07M1 is based on ST morpho connector, male pin headers (CN7 and CN10) accessible on both sides of the board. They can be used to connect this power board to NUCLEO-F302R8 board. All signals and power pins for MCU are available on ST morpho connector. For further details refer to UM1724 document (section 5.12 ST morpho connector) available on website www.st.com.

Figure 6. X-NUCLEO-IHM07M1 – top layer with silk-screen: A diagram of the top layer of the X-NUCLEO-IHM07M1 board, showing the placement of components, connectors (CN5, CN10, CN6, CN7, CN8, CN9), jumpers (JP1, JP2, JP3, J5, J6, J7, J9), potentiometer (SPEED), and integrated circuits (U11, U10).

Table 3. Connectors description (continued)

Figure 7. X-NUCLEO-IHM07M1 connectors view: A photograph of the X-NUCLEO-IHM07M1 board with specific connectors and jumpers highlighted and labeled, including JP1, JP2, J5, JP6, JP3, J9, SPEED, CN10, CN5, CN6, CN8, CN7, CN9, J2, J3, J7, and D11 (LED status indicator).

3.4 Upload the firmware example

The motor control Nucleo Pack example firmware is pre-loaded in NUCLEO-F302R8 board. As described in the previous section, it performs two different algorithms to run the motor, 6-step (trapezoidal control) or FOC (Field Oriented Control). This chapter describes the procedure to reload the firmware demonstration inside the NUCLEO-F302R8 board, in order to restart by default condition. There are two ways to do it: one is through ST-LINK tool (free download available from ST web site: www.st.com), and one with drag & drop function (suggested).

3.4.1 Drag & drop procedure:

1. Install ST-LINK drivers from www.st.com website.
2. On the NUCLEO-F302R8 board put JP5 jumper in U5V position.
3. Plug the NUCLEO-F302R8 Board to the host PC using a micro USB cable. If the ST-LINK driver is correctly installed, it will be recognized as an external memory device called "NUCLEO" or similar.
4. Take the binary file of the firmware demonstration (P-NUCLEO-IHM001.bin) and drag and drop the file into the "NUCLEO" device listed inside the disk drives list (this is showed by clicking the Start button of Windows OS interface), contained into X-CUBE-SPN7 firmware pack.
5. Wait until flashing is complete.

3.4.2 ST-LINK tool:

1. Open "ST-LINK tool".
2. Connect NUCLEO-F302R8 board to PC with a USB type A to Mini-B cable through USB connector (CN1) on NUCLEO-F302R8 board.
3. Make sure that the embedded ST-LINK/V2 is configured for in-system programming on NUCLEO-F302R8 board (both CN2 jumpers ON).
4. Use “P-NUCLEO-IHM001.bin“ binary file to upload the code inside STM32, the window will appear as shown in Figure 8.

Figure 8. ST-LINK utility tool: A screenshot of the STM32 ST-LINK Utility software displaying the memory display window, showing the loaded firmware file 'P-NUCLEO-IHM001.hex' and its memory address range.

5. Click on Target and Program buttons (see Figure 9: ST-LINK utility tool programming environment).

Figure 9. ST-LINK utility tool programming environment: A screenshot of the STM32 ST-LINK Utility software in programming mode, showing the interface for selecting and uploading firmware to the target microcontroller.

6. Click on Start and the firmware will be uploaded successfully.

4.1 6-step firmware based on X-CUBE-SPN7

4.1.1 Firmware architecture overview

The firmware example in X-CUBE-SPN7 is provided for three different IDE tools, in this case the IAR™ IDE workspace appears as shown in Figure 10.

Figure 10. 6-step firmware – Project workspace on IAR: A screenshot of the IAR Embedded Workbench IDE, displaying the project workspace for the 6-step firmware, including the project tree, source files, and code editor.

The firmware solution is built around three independent levels that can easily interact with each others as described in the below Figure 11: Generic firmware architecture:

Figure 11. Generic firmware architecture: A layered diagram illustrating the generic firmware architecture. Level 2 represents applications and demonstrations. Level 1 includes middleware components and examples. Level 0 comprises HAL Peripheral Drivers and BSP Drivers, interacting with the low-level driver core and hardware components.

Level 0:

This level is divided into three sub-layers:

• Board Support Package (BSP): this layer offers a set of APIs relative to the hardware components in the hardware boards (Audio codec, IO expander, Touchscreen, SRAM driver, LCD drivers. etc...) and composed of two parts:
  • Component: is the driver relative to the external device on the board and not related to the STM32. The component driver provides specific APIs to the BSP driver external components and could be portable on any other board. In this case (X-NUCLEO-IHM07M1) the ST L6230 driver has been provided inside the firmware package.
  • BSP driver: it allows to link the component driver to a specific board and provides a set of friendly used APIs. The APIs naming rule is BSP_FUNCT_Action(): ex. BSP_LED_Init(),BSP_LED_On().
  It is based on modular architecture, allowing to port it easily on any hardware by just implementing the low level routines.
• Hardware Abstraction Layer (HAL): this layer provides the low level drivers and the hardware interfacing methods to interact with the upper layers (application, libraries and stacks). It provides a generic, multi instance and functionalities oriented APIs which permit to offload the user application implementation, by providing ready to use process. For example, for the communication peripherals (I2S, UART...) it provides APIs allowing to initialize and configure the peripheral, manage data transfer based on polling, interrupt or DMA process, and manage communication errors that may raise during communication. The HAL drivers APIs are splitted in two categories: generic APIs which provides common and generic functions to all the STM32 series and extension APIs, which provides specific and customized functions for a specific family or a specific part number.
• Basic peripheral usage examples: this layer encloses the examples built over the STM32 peripheral using only the HAL and BSP resources.

Level 1:

This level is divided into two sub-layers:

• Middleware components: set of Libraries covering USB Host and device libraries, STemWin, FreeRTOS, FatFS, LwIP, and PolarSSL. Horizontal interactions between the components of this layer is done directly by calling the feature APIs, while the vertical interaction with the low level drivers is done through specific callbacks and static macros, implemented in the library system call interface. For example, the FatFs implements the disk I/O driver to access microSD drive or the USB Mass Storage Class. The middleware components provided with the X-CUBE-SPN7 package contain the core of the motor control algorithm: 6-step library (6Step_Lib.c/h) and interface files (stm32f302_ihm07m1.c/h). The interface file includes the map of STM32 MCU peripherals used (for instance, advanced TIMx, general TIMx, ADCx, DACx, UART etc.) to operate with the MC SixStep library. This file must be updated according with the modification done by the user through STM32CubeMX software, if channels or peripherals will be modified respect to the default configuration. At middleware level a serial communication based on UART with external PC terminal emulator has been included in X-CUBE-SPN7 package (see the UART_UI.c/h).
• Examples based on the middleware components: each middleware component comes with one or more examples (called also Applications), showing how to use it. Integration examples that use several middleware components are provided as well. This folder is created with STM32CubeMX software and it contains the main file for firmware initialization (peripherals, MC_6Step and UART communication). In addition a specific file (MC_SixStep_param.h) has been added to provide the complete list of parameters for MC-6Step library at application level. Inside the stm32fxxx_it.c file all interrupt handlers are defined and in particular it contains the starting point for UART communication.

Level 2:

This level is composed of a single layer which is global real-time and graphical demonstration based on the middleware service layer, the low level abstraction layer and the basic peripheral usage applications for board based functionalities.

The Figure 12: X-CUBE-SPN7 software architecture shows the firmware architecture of X-CUBE-SPN7 package, including also the HW components level.

Figure 12. X-CUBE-SPN7 software architecture: A block diagram showing the X-CUBE-SPN7 software architecture, detailing layers such as Utilities, CMSIS, Middleware (MC 6-Step library, User Interface), Drivers (Hardware Abstraction Layer API, Boards Support Packages), and HW Components (STM32, L6230, TSV994IPT, BAT30KFILM) on the STM32 Nucleo Board and X-NUCLEO-IHM07M1 Expansion Board.

4.1.2 Firmware parameter settings to spin different BLDC motors

The firmware example provided for P-NUCLEO-IHM001 kit is tuned for low inductance/high speed motor (reference part: Bull-Running model BR2804-1700kV, 11.1Vdc, 5A, 7 pole pairs, 19000 MaxRPM speed). The X-CUBE-SPN7 firmware package is developed to simplify the way to spin a different kind of motors with only few changes. In this case, a header file (MC_SixStep_param.h) contained inside X-CUBE-SPN7, includes several parameters organized in two sections: basic and advanced. In the first section it is possible to change the main parameters: for instance, motor pole pairs, clockwise or counter clockwise motor direction, target speed or potentiometer selection. In the advanced section, it is possible to set the PI parameters, define the alignment time or the acceleration rate during startup, change the zero crossing threshold and a lot of parameters usefully for system fine tuning.

In case of different motor connected or different load condition, after the reset or power-on, the firmware is able to reduce the acceleration rate if startup fails and, at the next push button event (on NUCLEO-F302R8 board), a new value speed profile will be generated.

After this changes the firmware is ready to be recompiled with IDE tool and uploaded in NUCLEO-F302R8 board.

4.1.3 Inside the 6-step firmware

The main.c file contains the starting point of 6-step library for motor control, in particular the MC_SixStep_INIT() configures the basic structure of MC driver based on 6-step control algorithm and the header file (6Step_Lib.h) provides the connection between the application layer with this driver. The stm32f3xx_it.c file includes the entry point for UART communication and the handling code for BKIN interrupt. Inside the example folder the stm32F302_nucleo_ihm07m1.c contains all the MCU related functions, header files and the complete list of the peripherals used.

4.1.4 DAC settings for debug

For debug purpose it is possible to use the DAC peripheral and configure the 6-step library, in order to drive the signal. The function SET_DAC_value(dac_value) allows to convert the variable "dac_value” in 16-bit format (with no sign) in analog signal so it is possible to monitor for instance the motor speed (set by default) or the potentiometer value through an external oscilloscope attached at configured pin. By default PA4 pin is configured and it is accessible through the ST morpho connector and it is typically connected to DAC_CH1 (NUCLEO-F302R8 board). Other pin are available at J7 connector according with the NUCLEO-F302R8 board used. For pin modification remember to modify also the stm32F302_nucleo_ihm07m1.h file. The DAC peripheral is on by default but it is possible to disable it through the MC_SixStep_param.h.

4.2 ST FOC SDK – Configuration guide for P-NUCLEO-IHM001

The demonstration board supports also the ST FOC library and no hardware modification is needed to run the motor with this control algorithm. In this case it is only needed to configure the board for current sensing (1-shunt or 3-shunt mode) and select the JP1, JP2 jumpers, according to the jumper settings shown on Table 1: Jumper settings. It is also available the support of MC Workbench software through the USB cable used for the NUCLEO programming. In this case it is recommended to configure the FOC SDK for USART2 on PA2 and PA3 pin.

For further information about ST FOC SDK library refer to STSW-STM32100 document on ST website: www.st.com.