Universal timer

The tutorial demonstrates the general timer (TIM3, TIM4) encoder interface mode to obtain the motor speed and print the motor speed through the serial port.

The tutorial only introduces the standard library project code

Hardware connection

Since we have configured a special connection line, we only need to install it to the corresponding interface:

Control principle

Use the encoding interface mode of TIM3 and TIM4 of the general timer on the STM32F103RCT6 development board to count the encoder signal of the motor.

• General purpose timer

• 520 motor

Count value

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4: represents encoder frequency multiplication
According to the count value of one rotation, the speed of the car can be calculated. This tutorial does not involve speed conversion

• Encoder reading

Get the count value by directly reading the timer CNT register value.

The tutorial sets counting on TI1 and TI2, sets the encoder mode to 4 times frequency, and the input signal is not reversed;

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Whether the counter counts up or down depends on the AB phase signal

Pin definition

Software code

Since the default function of the pin is the normal IO pin function, we need to use the multiplexing function.

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Product supporting materials source code path: Attachment → Source code summary → 1.Base_Course → 8.General_Timer

Control function

The tutorial only briefly introduces the code, you can open the project source code to read the details.

Encoder_Init_TIM3

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void Encoder_Init_TIM3(void)
{
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    TIM_ICInitTypeDef TIM_ICInitStructure;
    GPIO_InitTypeDef GPIO_InitStructure;
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE); //Enable timer 3 clock
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE); //Enable PA port clock

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6|GPIO_Pin_7; //Port configuration
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING; //Floating input
    GPIO_Init(GPIOA, &GPIO_InitStructure); //Initialize GPIOA according to the set parameters

    TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
    TIM_TimeBaseStructure.TIM_Prescaler = 0; // Prescaler
    TIM_TimeBaseStructure.TIM_Period = ENCODER_TIM_PERIOD; //Set the counter auto-reload value
    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; //Select clock division: no division
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; /////TIM counts up
    TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
    TIM_EncoderInterfaceConfig(TIM3, TIM_EncoderMode_TI12, TIM_ICPolarity_Rising, TIM_ICPolarity_Rising);//Use encoder mode 3
    TIM_ICStructInit(&TIM_ICInitStructure);
    TIM_ICInitStructure.TIM_ICFilter = 10; //Filter 10
    TIM_ICInit(TIM3, &TIM_ICInitStructure);
    TIM_ClearFlag(TIM3, TIM_FLAG_Update);//Clear TIM update flag
    TIM_ITConfig(TIM3, TIM_IT_Update, ENABLE);
    //Reset counter
    TIM_SetCounter(TIM3,0);
    TIM_Cmd(TIM3, ENABLE);
}

Encoder_Init_TIM4

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void Encoder_Init_TIM4(void)
{
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    TIM_ICInitTypeDef TIM_ICInitStructure;
    GPIO_InitTypeDef GPIO_InitStructure;
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE); //Enable the clock of timer 4
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE); //Enable the clock of PB port

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6|GPIO_Pin_7; //Port configuration
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING; //Floating input
    GPIO_Init(GPIOB, &GPIO_InitStructure); //Initialize GPIOB according to the set parameters
    TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
    TIM_TimeBaseStructure.TIM_Prescaler = 0x0; // Prescaler
    TIM_TimeBaseStructure.TIM_Period = ENCODER_TIM_PERIOD; // Set counter auto-reload value
    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; // Select clock division: no division
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; /////TIM counts up
    TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);
    TIM_EncoderInterfaceConfig(TIM4, TIM_EncoderMode_TI12, TIM_ICPolarity_Rising, TIM_ICPolarity_Rising); // Use encoder mode 3
    TIM_ICStructInit(&TIM_ICInitStructure); TIM_ICInitStructure.TIM_ICFilter = 10; TIM_ICInit(TIM4, &TIM_ICInitStructure); 
    TIM_ClearFlag(TIM4, TIM_FLAG_Update);//Clear the TIM update flag TIM_ITConfig(TIM4, TIM_IT_Update, ENABLE); //Re set counter TIM_SetCounter(TIM4,0); TIM_Cmd(TIM4, ENABLE);
}

Read_Encoder

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int Read_Encoder(Motor_ID MYTIMX)
{
   int Encoder_TIM;    
   switch(MYTIMX)
     {
         case MOTOR_ID_ML:  Encoder_TIM= (short)TIM3 -> CNT;  TIM3 -> CNT=0;break;  
         case MOTOR_ID_MR:  Encoder_TIM= (short)TIM4 -> CNT;  TIM4 -> CNT=0;break;  
         default: Encoder_TIM=0;
     }
        return Encoder_TIM;
}

TIM3_IRQHandler

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void TIM3_IRQHandler(void)
{
    if(TIM3->SR&0X0001)// The overflow is interrupted
    {
    }
    TIM3->SR&=~(1<<0); // Clears the interrupt flag bit
}

TIM4_IRQHandler

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void TIM4_IRQHandler(void)
{
    if(TIM4->SR&0X0001)//Overflow interrupt
    {
    }
    TIM4->SR&=~(1<<0);//Clear interrupt flag
}

Experimental phenomenon

The General_Timer.hex file generated by the project compilation is located in the OBJ folder of the General_Timer project. Find the General_Timer.hex file corresponding to the project and use the FlyMcu software to download the program into the development board.

After the program is successfully downloaded: Use the serial port debugging assistant to see the encoder count information printed by the serial port.

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When using the serial port debugging assistant, you need to pay attention to the serial port settings. If the settings are wrong, the phenomenon may be inconsistent.