K230 Vision Line Tracking

This tutorial is a comprehensive experiment combining multiple peripherals. You can understand individual peripherals before conducting this experiment.

1. Software-Hardware Requirements

• KEIL5

• MSPM0G3507 Robot Development Board

  K230 Module: External

• Type-C Data Cable or DAP-Link

  For program download or simulation to the development board

2. Brief Principle

2.1 Hardware Schematic Diagram

2.2 Physical Connection Diagram

Wiring Pins

Motor Wiring (Note: The wiring in the diagram below is for position reference only. We provide dual-head PH2.0 6Pin all-black cables with anti-mistake design, so you don't need to worry about wiring issues)

K230 Wiring (Note: The wiring in the diagram below is for position reference only. We provide K230 dual-head PH2.0 4Pin all-black cables with anti-mistake design, so you don't need to worry about wiring issues)

2.3 Control Principle

• Program Flow Chart

Control Principle:

PID Control

PID control is a commonly used closed-loop control algorithm that continuously adjusts the controller output to minimize the error between the system's actual output and expected output.

Communication Protocol:

When k230 recognizes the color track, it will send a data frame via serial port with the following format

Microcontroller part:

Receive data sent by k230 via serial port and process each byte of data. Extract valid data from the data frame content and store it in an array. Then perform PID processing on the array data, and the microcontroller drives the motors based on the processed data to move along the track.

3. Code Analysis

Main Function Analysis

Function: Pto_Loop

Partial Function Analysis

• main.c

​x
ColorMode color_mode = 1;  //1:巡线、2:跟踪  1: Patrol, 2: Tracking
​
int main(void)
{
    
    bsp_init();//需要的外设初始化 / Required peripheral initialization  
    Control_RGB_ALL(OFF);//关闭RGB / Turn off RGB
    delay_ms(100);                                                                                                OLED_ShowString(0,0,"pid_output:",8,1);//显示pid输出用于控制左右 / Display pid output for controlling left and right
    OLED_ShowString(0,20,"pid_output1:",8,1);//显示pid输出用于控制前后 / Display pid output for controlling forward and backward
    OLED_Refresh();
                
            
    while (1) 
    {   
            Pto_Loop();
            OLED_ShowSNum(75,0, pid_output, 3, 8, 1);
            OLED_ShowSNum(75,20,pid_output1,3,8,1);
            OLED_Refresh();
                
    }
}
​

color_mode：Use 1 when running vision line tracking case, use 2 when running color tracking case

BSP_init：Hardware initialization

pto__Loop：Continuously processes received K230 messages.

• yb_protocol.c

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/**
 * @Brief: 数据分析 Data analysis
 * @Note: 
 * @Parm: 传入接受到的一个数据帧和长度    Pass in a received data frame and length
 * @Retval: 
 */
void Pto_Data_Parse(uint8_t *data_buf, uint8_t num)
{
    uint8_t pto_head = data_buf[0];
    uint8_t pto_tail = data_buf[num-1];
    
    //校验头尾  Check head and tail
    if (!(pto_head == PTO_HEAD && pto_tail == PTO_TAIL))
    {
​
        return;
    }
    
    uint8_t data_index = 1;
    uint8_t field_index[PTO_BUF_LEN_MAX] = {0};
    int i = 0;
    int values[PTO_BUF_LEN_MAX] = {0};
    char msgs[][PTO_BUF_LEN_MAX] = {0};
    
    //分割字段  Split fields  
    for (i = 1; i < num-1; i++)
    {
        if (data_buf[i] == ',')
        {
            data_buf[i] = 0;
            field_index[data_index] = i;
            data_index++;
        }
    }
    
    //解析长度与功能ID  Parse length and function ID  
    for (i = 0; i < 2; i++)
    {
        values[i] = Pto_Char_To_Int((char*)data_buf+field_index[i]+1);
    }
    
    uint8_t pto_len = values[0];
    uint8_t pto_id = values[1];
​
    ParseCommonFields(pto_id,data_buf,pto_len,field_index,data_index,values,msgs);
​
}
​
​

Parse the received protocol-compliant data to obtain the function ID number and data information in the data, and execute the corresponding function processing function. This project uses a metadata parsing method. The core idea is to separate the protocol format description (field position, type, etc.) from the parsing logic, define the protocol format through data structures (such as struct arrays), and the parsing function automatically processes data according to these descriptions.

Different types of data contained in the protocol can also be parsed. If you want to understand the implementation details, you can study it yourself. No excessive explanation will be provided. This function has been adapted to all K230 communication protocols in our store. You don't need to fully understand it to use it normally.

• bsp_PID_motor.c

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// PID单独计算一条通道  / PID calculation for a single channel
float PID_Calc_One_Motor(uint8_t motor_id, float now_speed)
{
    if (motor_id >= MAX_MOTOR)
        return 0;
​
        return PID_Location_Calc(&pid_motor[motor_id], now_speed);
        
        
}
​
void Set_PID_Motor(float set_l ,float set_r,float turn_out)
{
        
        
        l_pid_out = PID_Calc_One_Motor(0, set_l);
        r_pid_out = PID_Calc_One_Motor(1, set_r);
​
        PWM_Control_Car(l_pid_out+turn_out , r_pid_out-turn_out );
​
}
​
// 位置式PID计算方式 / Positional PID calculation method
​
float PID_Location_Calc(PID_t *pid, float actual_val)
{
    /*计算目标值与实际值的误差*/ /*Calculate error between target value and actual value*/
​
    pid->err = pid->target_val - actual_val;
​
    /* 限定闭环死区 */ /* Limit closed-loop dead zone */
​
    if ((pid->err >= -40) && (pid->err <= 40))
    {
        pid->err = 0;
        pid->integral = 0;
    }
​
    /* 积分分离，偏差较大时去掉积分作用 */ /* Integral separation, remove integral effect when deviation is large */
​
    if (pid->err > -1500 && pid->err < 1500)
    {
        pid->integral += pid->err; // error accumulation 误差累积 / Error accumulation
​
        /* Limit the integration range to prevent integration saturation 限定积分范围，防止积分饱和 */
        if (pid->integral > 4000)
            pid->integral = 4000;
        else if (pid->integral < -4000)
            pid->integral = -4000;
    }
​
    /*PID算法实现*/ /*PID algorithm implementation*/ 
    pid->output_val = pid->Kp * pid->err +
                      pid->Ki * pid->integral +
                      pid->Kd * (pid->err - pid->err_last);
        
​
    /*误差传递*/ /*Error transmission*/ 
    pid->err_last = pid->err;
​
    /*返回当前实际值*/ /*Return current actual value*/ 
    return pid->output_val;
}
​

Set_PID_Motor：Set target values for 2 motors and steering loop output value.

PID_Calc_One_Motor：Calculate position loop PID value for one channel and return the calculated value.

PID_Location_Calc：Position loop PID calculation formula and complete position loop structure.

• bsp_K230_control.c

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void Visual_Line_Track(int x,int w)
{
    PID_TypeDef k230_pid;
    PID_param_init(&k230_pid);
​
    set_p_i_d(&k230_pid, k230_p, k230_i, k230_d);
    
    if(!Wait_Flag)
    {
        delay_ms(1000);delay_ms(1000);delay_ms(1000);//delay 3s / Delay 3 seconds
        Wait_Flag = 1;
        return;
    }
    
    int16_t err = 300 - (x + w/2);//获取x轴上的差值  / Get difference value on x-axis
​
    if(err<5 && err>-5)err=0;
    
    pid_output = PID_Calculate(&k230_pid,err);//计算差值的PID  / Calculate PID of difference value  
​
    
    Set_PID_Motor(100 ,100,pid_output);
}
​
​

Visual_Line_Track：After receiving data from K230, press the reset button, then wait for three seconds, then start calculating the line tracking PID value, and finally control the car.

4. Experimental Operation

1. Wire according to the hardware wiring instructions in the tutorial.
2. Open the project used by MSPM0G3507. First, check the beginning part of the main.c file and modify color_mode to 2. This enables tracking mode. After correct modification, compile and burn the program. Finally, reset or power on again.
3. Place Visual_line_tracking.py in the root directory of K230's SD card and rename it to main.py, then reset or power on again.

If you are not clear about how to burn programs into K230, please first check the K230 Vision Module tutorial's [Quick Start] chapter.

4. Place the car in the line tracking map, adjust the K230 module bracket to a suitable angle, and connect the power.
5. When K230 initialization is successful, it will start recognizing the set color. Then press the car reset button, wait for three seconds, and the car will start line tracking.

Note:

Visual_line_tracking.py provides recognition of four preset colors: red, green, blue, and black. If the recognition effect is not good, you can check the K230 color recognition tutorial to learn how to replace LAB thresholds with thresholds suitable for your environment.

Here you can modify to the color you want to track:

If you are not satisfied with the line tracking effect, you can modify the PID values in the bsp_PID_motor.c file of the APP project.

5. Experimental Phenomena

Turn on the power switch, wait for system initialization to complete, the screen will display the camera image and will frame the color you want to track. After waiting for three seconds, the car will start driving along the line.