基于C语言编写atmega128的bootloader程序

以下是一个基于 C 语言编写的 ATmega128 Bootloader 程序的示例代码：

#include <avr/io.h>
#include <avr/boot.h>
#include <avr/interrupt.h>

#define BAUD 9600
#define F_CPU 8000000UL

#define UART_BAUDRATE (((F_CPU / (BAUD * 16UL))) - 1)

void uart_init(void)
{
    UBRR0H = (uint8_t)(UART_BAUDRATE >> 8);
    UBRR0L = (uint8_t)(UART_BAUDRATE);
    UCSR0B = (1 << TXEN0) | (1 << RXEN0);
    UCSR0C = (1 << UCSZ01) | (1 << UCSZ00);
}

void uart_putc(uint8_t data)
{
    while (!(UCSR0A & (1 << UDRE0)));
    UDR0 = data;
}

void uart_puts(char *str)
{
    while (*str)
    {
        uart_putc(*str++);
    }
}

void jump_to_app(void)
{
    void (*app_start_addr)(void) = 0x0000;
    app_start_addr();
}

int main(void)
{
    uart_init();
    sei();

    uart_puts("ATmega128 Bootloader\r\n");

    if (!(PINB & (1 << PINB0)))
    {
        uart_puts("Entering Bootloader Mode\r\n");

        while (1)
        {
            uint8_t data = uart_getc();

            if (data == 'u')
            {
                uart_puts("Unlocking Application\r\n");
                boot_lock_bits(0x00);
            }
            else if (data == 'e')
            {
                uart_puts("Erasing Application\r\n");
                boot_page_erase(0x0000);
                boot_spm_busy_wait();
            }
            else if (data == 'w')
            {
                uart_puts("Writing Application\r\n");

                uint16_t address = 0x0000;
                uint8_t *buffer = (uint8_t *)(0x0000);

                for (uint16_t i = 0; i < SPM_PAGESIZE; i += 2)
                {
                    uint16_t data = uart_getc();
                    data |= uart_getc() << 8;

                    buffer[i] = data & 0xFF;
                    buffer[i + 1] = data >> 8;
                }

                boot_page_write(address, buffer);
                boot_spm_busy_wait();
                boot_rww_enable();
            }
            else if (data == 'j')
            {
                uart_puts("Jumping to Application\r\n");
                jump_to_app();
            }
        }
    }
    else
    {
        jump_to_app();
    }

    return 0;
}

这个程序基于 UART 模块实现 ATmega128 的 Bootloader 功能。当启动程序时，它会检测 PINB0 引脚是否为低电平，如果是，则进入 Bootloader 模式，等待来自串口的指令，以擦除、编程和解锁 Flash 存储器。如果 PINB0 引脚为高电平，则跳转到应用程序地址开始执行应用程序。