基于密码的智能门锁项目编译错误求助（ATmega32）

错误信息 #

编译C文件：Test01.c
avr-gcc -c -mmcu=atmega32 -I. -gdwarf-2 -DF_CPU=8000000UL -Os -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums -Wall -Wstrict-prototypes -Wa,-adhlns=./Test01.lst  -std=gnu99 -MMD -MP -MF .dep/Test01.o.d Test01.c -o Test01.o
Test01.c: 在函数‘Getuserid’中：
Test01.c:166: 错误：使用了未定义的标签‘start’
make.exe: *** [Test01.o] 错误 1

问题背景 #

开发基于ATmega32微控制器的密码智能门锁项目，编译代码时触发上述错误。

原代码 #

#include <avr/io.h>
#include <avr/eeprom.h> //the EEPROM library
#include <util/delay.h>
#include <lcd.h>
#include <avr/interrupt.h>
#include <math.h>


//define KEYPAD IN C PORTS
#define KEYPAD_PORT PORTC
#define KEYPAD_DDR   DDRC
#define KEYPAD_PIN   PINC

unsigned int failedAttempts;



/////////////////////////////   EEPROM INITILIZE  AND CONFIGURATION   ///////////////////////////////////////////////////////////////

void EEPROM_write(unsigned int address, unsigned char data) {
    /* Wait for completion of previous write */
    while (EECR & (1 << EEWE));

    /* Set up address and Data Registers */
    EEAR = address;
    EEDR = data;

    /* Write logical one to EEMWE */
    EECR |= (1 << EEMWE);

    /* Start EEPROM write by setting EEWE */
    EECR |= (1 << EEWE);
}

char EEPROM_read(unsigned int address) {
    /* Wait for completion of previous write */
    while (EECR & (1 << EEWE));

    /* Set up address register */
    EEAR = address;

    /* Start EEPROM read by writing EERE */
    EECR |= (1 << EERE);

    /* Return data from Data Register */
    return EEDR;
}

unsigned int readEEPROM(int pos) {
    return ((EEPROM_read(pos + 1) * 100) + EEPROM_read(pos));
}

void writeEEPROM(unsigned int pos, unsigned int val) {
    unsigned int a = val % 100; // Last two digits of the password
    unsigned int b = val / 100; // First two digits of the password

    EEPROM_write(pos, a);
    EEPROM_write(pos + 1, b);
}

unsigned int validate_password(unsigned int entered_password) {
    unsigned int EEPROM_pos = 0;

    while (EEPROM_pos < 20) {
        if (readEEPROM(EEPROM_pos) == entered_password) {
            return 1;
        }

        EEPROM_pos += 2;
    }

    return 0;
}

//////////////////////////////   KEYPAD INTERFACING      /////////////////////////////////////////////////

unsigned int GetKeyPressed(void) {
    uint8_t r, c;
    KEYPAD_PORT |= 0x0F;

    for (c = 0; c < 4; c++) {
        KEYPAD_DDR &= ~(0xFF);

        KEYPAD_DDR |= (0x80 >> c);
        for (r = 0; r < 4; r++) {
            if (!(KEYPAD_PIN & (0x08 >> r))) {
                return (r * 3 + c);
            }
        }
    }

    return 0xFF; // Indicate No key pressed
}

unsigned int calcPass(unsigned int key, unsigned int position, unsigned int currentVal) {
    unsigned multi = 0;

    if (position == 0)
        multi = 1000;
    else if (position == 1)
        multi = 100;
    else if (position == 2)
        multi = 10;
    else if (position == 3)
        multi = 1;

    return currentVal + key * multi;
}

unsigned int Getpassword(void) {
    unsigned int key;
    unsigned int password = 0;
    unsigned int position = 0;

    LCDClear();

    while (position < 4) {
        while (GetKeyPressed() != 255) {
            key = GetKeyPressed();

            if (key < 10) {
                password = calcPass(key, position, password);
                LCDWriteStringXY(position, 0, "*");
                position++;
                _delay_ms(50);
            } else if (key == 10) {
                break;
            }
        }
    }

    return password;
}

unsigned int Getuserid(void) {
    volatile unsigned int userid = 0;
    volatile unsigned int position = 0;
    volatile unsigned int currentval = 0;
    volatile unsigned int multi;


    LCDClear();
    while (position < 2) {
        if (GetKeyPressed() < 10) {
            currentval = GetKeyPressed();
            if ((position == 0) && (currentval > 1)) {
                userid = currentval;
                LCDWriteIntXY(position, 0, currentval, 1);
                _delay_ms(50);
                break;
            }
            if (position == 0)
                multi = 10;
            else
                multi = 1;
            userid += multi * currentval;
            LCDWriteIntXY(position, 0, GetKeyPressed(), 1);
            position++;
        } else if (GetKeyPressed() == 10) {
            break;
        }
        _delay_ms(50);
    }
    volatile unsigned int rem = userid % 2;
    if ((userid > 18) || (rem == 1) || (userid >= EEPROM_read(20))) {
        goto start;
    }
    return userid;
}

void openDoor(void) {
    // Initially, the door is closed.
    PORTC = 1 << PC5; // Open the door
    LCDWriteStringXY(4, 0, "Welcome");
    _delay_ms(60000); // Open for 1 minute
    PORTC = 0;
}

void closeDoor(void) {
    PORTC = 1 << PC4;
    LCDClear();
    LCDWriteStringXY(0, 0, "Door closed");
    _delay_ms(200);
    PORTC = 0;
}

int main(void) {
    DDRC = 255;

    if (EEPROM_read(21) != 5) {
        // Runs only once
        EEPROM_write(20, 2);
        writeEEPROM(0x00, 1234); // Temporary user
        EEPROM_write(21, 5);
    }

    LCDInit(0); // Initialize LCD module, no cursor blinking

    LCDClear(); // Clear the screen

    while (GetKeyPressed() == 255) {
        LCDWriteStringXY(0, 0, "Please enter");
        LCDWriteStringXY(4, 1, "the Password");
    }

    while (1) {
        unsigned int password = Getpassword();

        if (validate_password(password) == 1) {
            LCDClear();
            openDoor();
            failedAttempts = 0; // Number of attempts
            unsigned int m = 600; // Wait for 1 minute to add a new user
            for (unsigned int i = 0; i < m; i++) {
                if (GetKeyPressed() == 12) { // To add a new user, press # key
                    if (EEPROM_read(20) < 20) {
                        LCDWriteStringXY(2, 0, "Add a new user");
                        _delay_ms(100);
                        unsigned int newpassword = Getpassword();
                        // Save a new user in EEPROM
                        writeEEPROM(EEPROM_read(20), newpassword);
                        LCDClear();
                        LCDWriteStringXY(2, 0, "User ID:");
                        LCDWriteIntXY(2, 1, EEPROM_read(20), 2);
                        EEPROM_write(20, EEPROM_read(20) + 2);
                        i = 0;
                        _delay_ms(100);
                    } else {
                        LCDWriteStringXY(2, 0, "Max no of");
                        LCDWriteStringXY(6, 1, "users entered.");
                        _delay_ms(100);
                    }
                } else if (GetKeyPressed() == 11) { // Reset the passwords, press 0 key
                    LCDWriteStringXY(2, 0, "Add user id");
                    _delay_ms(100);
                    unsigned int newuser = Getuserid();
                    _delay_ms(100);
                    LCDWriteStringXY(0, 0, "Add new password");
                    _delay_ms(100);
                    unsigned int newpassword = Getpassword();
                    _delay_ms(100);
                    writeEEPROM(newuser, newpassword);
                    LCDClear();
                    LCDWriteStringXY(0, 0, "Password Changed!");
                    _delay_ms(100);
                    i = 0;
                }
                LCDClear();
                _delay_ms(1);
            }
            closeDoor();
        } else {
            LCDClear();
            LCDWriteStringXY(1, 0, "Password Error!");
            failedAttempts++;

            if (failedAttempts > 3) {
                LCDClear();
                LCDWriteStringXY(0, 0, "Try Again Later!");
                _delay_ms(180000);
            }
            _delay_ms(200);
        }
    }
}

错误原因 #

在Getuserid函数中使用了goto start;语句，但函数内未定义start标签，导致编译器报错。

修复方案 #

方案1：补全start标签（快速解决编译问题） #

在Getuserid函数的用户ID输入逻辑开头添加start:标签，让goto可以跳转到函数开头重新输入：

unsigned int Getuserid(void) {
    volatile unsigned int userid = 0;
    volatile unsigned int position = 0;
    volatile unsigned int currentval = 0;
    volatile unsigned int multi;

start: // 新增标签，匹配goto语句
    LCDClear();
    while (position < 2) {
        // 原有输入逻辑代码
    }
    volatile unsigned int rem = userid % 2;
    if ((userid > 18) || (rem == 1) || (userid >= EEPROM_read(20))) {
        goto start; // 现在标签存在，编译通过
    }
    return userid;
}

方案2：用循环替代goto（推荐，代码结构更清晰） #

将用户ID输入逻辑改为循环结构，直到输入合法的ID，避免使用goto：

unsigned int Getuserid(void) {
    volatile unsigned int userid = 0;
    volatile unsigned int position = 0;
    volatile unsigned int currentval = 0;
    volatile unsigned int multi;

    while(1) { // 循环直到输入合法ID
        userid = 0;
        position = 0;
        LCDClear();
        while (position < 2) {
            if (GetKeyPressed() < 10) {
                currentval = GetKeyPressed();
                if ((position == 0) && (currentval > 1)) {
                    userid = currentval;
                    LCDWriteIntXY(position, 0, currentval, 1);
                    _delay_ms(50);
                    break;
                }
                if (position == 0)
                    multi = 10;
                else
                    multi = 1;
                userid += multi * currentval;
                LCDWriteIntXY(position, 0, GetKeyPressed(), 1);
                position++;
            } else if (GetKeyPressed() == 10) {
                break;
            }
            _delay_ms(50);
        }
        volatile unsigned int rem = userid % 2;
        if ((userid > 18) || (rem == 1) || (userid >= EEPROM_read(20))) {
            // 提示无效ID，等待后重新输入
            LCDClear();
            LCDWriteStringXY(0,0,"Invalid ID!");
            _delay_ms(1000);
            continue;
        } else {
            // 输入合法，返回用户ID
            return userid;
        }
    }
}

说明 #

• 方案1直接补全标签，快速解决编译错误，适合临时调试；
• 方案2采用结构化循环，代码可读性和可维护性更强，符合嵌入式编程的最佳实践。

内容的提问来源于stack exchange，提问作者Tharani Jayawardena