对stm32f103c8t6单片机，要求Timer1产生250Hz的定时器中断，在中断服务函数内，ADC单次采样三个通道的信号，并通过usart2发送三路ADC采样数值，此外还需要满足：在相邻的两次中断分别让两个GPIO交替产生1ms正脉冲信号

好的，根据您的要求，我提供一个参考代码实现，需要您在代码中设置好ADC采样的通道和USART发送的引脚等参数。代码如下：

#include "stm32f10x.h"
#include <stdio.h>

#define TIM_PERIOD      64000   // 定时器周期，对应250Hz的定时器中断频率

void TIM1_UP_IRQHandler(void)
{
    static uint8_t gpio_state = 0;

    if (TIM_GetITStatus(TIM1, TIM_IT_Update) != RESET) 
    {
        TIM_ClearITPendingBit(TIM1, TIM_IT_Update);

        // 交替产生1ms正脉冲信号
        if (gpio_state == 0)
        {
            GPIO_SetBits(GPIOA, GPIO_Pin_0);
            GPIO_ResetBits(GPIOA, GPIO_Pin_1);
            gpio_state = 1;
        }
        else
        {
            GPIO_ResetBits(GPIOA, GPIO_Pin_0);
            GPIO_SetBits(GPIOA, GPIO_Pin_1);
            gpio_state = 0;
        }

        // ADC采样
        ADC_SoftwareStartConvCmd(ADC1, ENABLE);
        while(!ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC));
        uint16_t adc_value1 = ADC_GetConversionValue(ADC1);

        ADC_SoftwareStartConvCmd(ADC2, ENABLE);
        while(!ADC_GetFlagStatus(ADC2, ADC_FLAG_EOC));
        uint16_t adc_value2 = ADC_GetConversionValue(ADC2);

        ADC_SoftwareStartConvCmd(ADC3, ENABLE);
        while(!ADC_GetFlagStatus(ADC3, ADC_FLAG_EOC));
        uint16_t adc_value3 = ADC_GetConversionValue(ADC3);

        // USART发送ADC采样值
        char buffer[50];
        sprintf(buffer, "ADC1: %d, ADC2: %d, ADC3: %d\n", adc_value1, adc_value2, adc_value3);
        int len = strlen(buffer);
        for (int i = 0; i < len; i++)
        {
            USART_SendData(USART2, buffer[i]);
            while (USART_GetFlagStatus(USART2, USART_FLAG_TXE) == RESET);
        }
    }
}

void TIM1_Configuration(void)
{
    TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
    NVIC_InitTypeDef        NVIC_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);
    TIM_TimeBaseStructure.TIM_Period = TIM_PERIOD - 1;
    TIM_TimeBaseStructure.TIM_Prescaler = 71;
    TIM_TimeBaseStructure.TIM_ClockDivision = 0;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);

    TIM_ITConfig(TIM1, TIM_IT_Update, ENABLE);
    TIM_Cmd(TIM1, ENABLE);

    NVIC_InitStructure.NVIC_IRQChannel = TIM1_UP_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
}

void ADC_Configuration(void)
{
    ADC_InitTypeDef         ADC_InitStructure;
    GPIO_InitTypeDef        GPIO_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1 | RCC_APB2Periph_ADC2 | RCC_APB2Periph_ADC3, ENABLE);

    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_2;
    GPIO_Init(GPIOC, &GPIO_InitStructure);

    ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;
    ADC_InitStructure.ADC_ScanConvMode = DISABLE;
    ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
    ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_None;
    ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
    ADC_InitStructure.ADC_NbrOfChannel = 1;
    ADC_Init(ADC1, &ADC_InitStructure);
    ADC_Init(ADC2, &ADC_InitStructure);
    ADC_Init(ADC3, &ADC_InitStructure);

    ADC_RegularChannelConfig(ADC1, ADC_Channel_10, 1, ADC_SampleTime_239Cycles5);
    ADC_RegularChannelConfig(ADC2, ADC_Channel_11, 1, ADC_SampleTime_239Cycles5);
    ADC_RegularChannelConfig(ADC3, ADC_Channel_12, 1, ADC_SampleTime_239Cycles5);

    ADC_Cmd(ADC1, ENABLE);
    ADC_Cmd(ADC2, ENABLE);
    ADC_Cmd(ADC3, ENABLE);
}

void USART_Configuration(void)
{
    GPIO_InitTypeDef        GPIO_InitStructure;
    USART_InitTypeDef       USART_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_AFIO, ENABLE);
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    USART_InitStructure.USART_BaudRate = 115200;
    USART_InitStructure.USART_WordLength = USART_WordLength_8b;
    USART_InitStructure.USART_StopBits = USART_StopBits_1;
    USART_InitStructure.USART_Parity = USART_Parity_No;
    USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
    USART_InitStructure.USART_Mode = USART_Mode_Tx;
    USART_Init(USART2, &USART_InitStructure);

    USART_Cmd(USART2, ENABLE);
}

int main(void)
{
    TIM1_Configuration();
    ADC_Configuration();
    USART_Configuration();

    GPIO_InitTypeDef        GPIO_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    while(1);
}

注意，代码仅作为参考，需要您根据具体的硬件连接和参数设置进行修改。