Servo control

This tutorial demonstrates: using the basic timer (TIM7) interrupt to simulate PWM control of the external S1 interface servo on the development board.

The first tutorial in this chapter will be more detailed than the following tutorials. The purpose is to demonstrate from the new project to the complete effect, and guide users how to use STM32CubeIDE to develop

1. Software-Hardware

STM32F103CubeIDE
STM32 Robot Development Board
180° servo
Type-C data cable or ST-Link
Download programs or simulate the development board

2. Brief principle

1. Hardware schematic diagram

2. Physical connection diagram

Note: Refer to the color of the servo wire for servo wiring. This experiment requires connecting 5V and GND jumper caps

Steering gear	Development board
VCC(red)	5V
SIG(yellow)	S1/S2/S3/S4
GND(brown)	GND

3. Control principle

By changing the duty cycle of the PWM signal, the angle of rotation of the servo is controlled

PWM（Pulse Width Modulation）

PWM is the abbreviation of pulse width modulation, which is a technology that controls the level by adjusting the pulse width of the signal.

Period: The duration of a complete PWM waveform;

Duty cycle: the ratio of high level duration to cycle time;

Frequency: The reciprocal of the period is called frequency, which is the number of PWM cycles generated per second;

PWM servo

Set the period of the PWM control signal to 20ms, which is a frequency of 50Hz; the high level time of the pulse determines the angle of rotation of the servo.

High level pulse width corresponding to common angles

Steering gear (180°)	High level pulse width (us)
0°	500
45°	1000
90°	1500
135°	2000
180°	2500

Basic timer

Using the TIM7 timer interrupt function on the STM32F103ZET6 development board

PWM servo (schematic name)	Control pin	Function
S1	PB0	Analog PWM output control S1 servo
S2	PB1	Analog PWM output control S2 servo
S3	PD14	Analog PWM output control S3 servo
S4	PD15	Analog PWM output control S4 servo


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For basic knowledge of basic timers, please refer to [3. Basic Development Board Tutorial: Basic Timers]

Timing formula

T (s) = \frac{(A R R + 1) * (P S C + 1)}{T I M_C L K (H z)}

Timing time of this project: 10us

T (s) = \frac{(A R R + 1) * (P S C + 1)}{T I M_C L K (H z)} = \frac{(9 + 1) * (71 + 1)}{72000000 (H z)} = 0.00001 s = 10 u s

3. Engineering experience

Use the project files we provide to directly experience the corresponding functions of the development board.

Later tutorials do not provide this content to avoid duplication of content. You can go to [2. Development environment construction and use: engineering experience and transplantation] to view the operation

1. Open the project

Project file location
Project file path: Under the [Project Source Code] folder of the Chapter 4 tutorial

Open project file

Copy the project file to the directory of English path, use STM32CubeIDE to open the project file, open the project file and select the .project file


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Tip: You can create a new STM32 folder on the desktop and select the STM32 folder as the workspace when opening the project file.

4. Project configuration

This tutorial will completely demonstrate the configuration process. Later, the content of new project, chip selection, project settings, pin settings of SYS, RCC configuration, clock configuration and project configuration will be omitted. Any changes will be stated in the tutorial. .

1. New project

Select workspace
The path of a new project or the path of an existing project file: the path cannot contain Chinese characters

New Project

2、chip selection

3、Project settings

project name

Firmware version

4、Pin configuration

SYS

RCC

TIM

NVIC

GPIO


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Please refer to the figure above for specific configuration options. It is recommended to add tags. STM32CubeIDE will generate corresponding macro definitions.

5、Clock configuration


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Refer to the options covered by the red arrows

6、Project configuration

Project
do not need to change

Code Generator

Advanced Settings

7、Generate code

Click on the "pinion" icon


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Click here to save or the Ctrl+C shortcut key to generate code.

Edit code
User code must be located between USER CODE BEGIN and USER CODE END.

The above is the peripheral configuration and initialization code generation.

5. Main functions

It mainly introduces the functional code written by the user. For detailed code, you can open the project file provided by us yourself and enter the Bsp folder to view the source code.

1. User function

Function: PwmServo_Handle

Function prototype	void PwmServo_Handle(void)
Function description	Called in timer interrupt, simulate output PWM signal
Input parameters	None
Output parameters	None
Notes	This function is called by the timer update interrupt callback function HAL_TIM_PeriodElapsedCallback

Function: PwmServo_Angle_To_Pulse

Function prototype	uint16_t PwmServo_Angle_To_Pulse(uint8_t angle)
Function description	Convert the specified angle into pulse width value
Input parameters	angle: rotation angle
Output parameters	Pulse width value

Function: PwmServo_Init

Function prototype	void PwmServo_Init(void)
Function description	Set the initial angle of each servo to 90°
Input parameters	None
Output parameters	None

Function: PwmServo_Set_Angle

Function prototype	void PwmServo_Set_Angle(uint8_t index, uint8_t angle)
Function description	Set the initial angle of a single servo
Input parameter 1	index: servo serial number
Input parameter 2	angle: rotation angle
Output parameters	None

Function: PwmServo_Set_Angle_All

Function prototype	void PwmServo_Set_Angle_All (uint8_t angle_s1, uint8_t angle_s2, uint8_t angle_s3, uint8_t angle_s4)
Function description	Set all servo rotation angles
Input parameter 1	S1 servo rotation angle
Input parameter 2	S2 servo rotation angle
Input parameter 3	S3 servo rotation angle
Input parameter 4	S4 servo rotation angle
Output parameters	None

2. HAL library function analysis

Function: HAL_GPIO_Init

Function prototype	void HAL_GPIO_Init(GPIO_TypeDef GPIOx, GPIO_InitTypeDef GPIO_Init)
Function description	Initialize GPIO pin parameters
Input parameter 1	GPIOx: Set the GPIO port, x takes the value A, B, C, D, E, F, G
Input parameter 2	GPIO_Init: GPIO initialization structure
Output parameters	None

Function: HAL_GPIO_WritePin

Function prototype	void HAL_GPIO_WritePin(GPIO_TypeDef *GPIOx, uint16_t GPIO_Pin, GPIO_PinState PinState)
Function Description	Set/Clear the specified pin
Input parameter 1	GPIOx: Set the GPIO port, x takes the value A, B, C, D, E, F, G
Input parameter 2	GPIO_Pin: Set the GPIO pin, x value is 0-15
Input parameter 3	PinState: Bit_RESET: clear the data port bit (low level); Bit_SET: set the data port bit (high level)
Output parameters	None

Function: HAL_TIM_Base_Init

Function prototype	HAL_StatusTypeDef HAL_TIM_Base_Init(TIM_HandleTypeDef *htim)
Function description	Initialize timer time base unit
Input parameters	htim: timer handle address
Output parameters	HAL status value: HAL_OK, HAL_ERROR, HAL_BUSY, HAL_TIMEOUT
Notes	This function will call the MCU underlying initialization function HAL_TIM_Base_MspInit to complete the settings of pins, clocks and interrupts

Function: HAL_TIM_Base_MspInit

Function prototype	void HAL_TIM_Base_MspInit(TIM_HandleTypeDef *htim);
Function description	Initialize the peripheral clock, GPIO and NVIC of the timer
Input parameters	htim: timer handle address
Output parameters	None

Function: HAL_TIM_Base_MspDeInit

Function prototype	void HAL_TIM_Base_MspDeInit(TIM_HandleTypeDef *htim)
Function description	Cancel the initialization of timer peripheral clock, GPIO and NVIC
Input parameters	htim: timer handle address
Output parameters	None

HAL_TIM_IRQHandler: timer interrupt service function

Function prototype	void HAL_TIM_IRQHandler(TIM_HandleTypeDef *htim)
Function description	Timer interrupt service function
Input parameters	htim: timer handle address
Output parameters	None
Notes	Internally, this function needs to first determine the interrupt type and clear the corresponding interrupt flag bit, and finally call the callback function

HAL_TIM_PeriodElapsedCallback: Timer update interrupt callback function

Function prototype	void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
Function description	Timer update interrupt callback function
Input parameters	htim: timer handle address
Output parameters	None
Notes	This function is called by HAL_TIM_IRQHandler, and specific processing tasks can be written internally

6. Program download

1. Serial port download

Generate .hex file: Left-click the project → select "Properties"

Check the corresponding option


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hex file location: under the Debug folder of the project file

Program Download
Use the Type-C data cable to connect the development board and the computer. For more detailed burning process, please refer to [2. Development environment construction and use: program download and simulation]


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Pay attention to the contents selected in the red box, which must be consistent

2、ST-Link Download

Debug Settings: ST-Link → SWD

Program Download: Click the Debug icon

7. Experimental Phenomenon

After downloading the program successfully, press the RESET button of the development board and observe the development board phenomenon!


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For program download, please refer to [2. Development environment construction and use: program download and simulation]

Phenomenon:

S1 interface servo: cyclic rotation from 0° → 45° → 90° → 135° → 180° → 135° → 90° → 45° → 0°.


The provided project only controls the S1 interface servo. You can modify the interface function parameters by yourself to control other servos.
For experimental phenomena, please see [Servo Control_Experimental Phenomenon.mp4]