当单片机接收到PC机发送的指定指令，通过串口，讲采集的温度发送到PC机，通过串口助手显示出来代码

好的，以下是一个示例代码，可以让你了解如何在单片机中实现这个功能。这个代码是基于STM32F103C8T6开发板，使用Keil MDK编写的。

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

#define USART_RX_BUF_SIZE   64
#define USART_TX_BUF_SIZE   64

uint8_t usart_rx_buf[USART_RX_BUF_SIZE];
uint8_t usart_tx_buf[USART_TX_BUF_SIZE];
uint8_t usart_rx_len = 0;

void USART1_Init(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    USART_InitTypeDef USART_InitStructure;
    NVIC_InitTypeDef NVIC_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_USART1, ENABLE);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
    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_10;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    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_Rx | USART_Mode_Tx;
    USART_Init(USART1, &USART_InitStructure);

    NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

    USART_Cmd(USART1, ENABLE);
    USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);
}

void USART1_IRQHandler(void)
{
    if (USART_GetITStatus(USART1, USART_IT_RXNE) != RESET)
    {
        uint8_t ch = USART_ReceiveData(USART1);
        if (usart_rx_len < USART_RX_BUF_SIZE)
        {
            usart_rx_buf[usart_rx_len++] = ch;
        }
        USART_ClearITPendingBit(USART1, USART_IT_RXNE);
    }
}

void USART1_SendString(char *str)
{
    while (*str)
    {
        USART_SendData(USART1, (uint8_t)*str++);
        while (USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET);
    }
}

void delay_ms(uint32_t ms)
{
    uint32_t i, j;
    for (i = 0; i < ms; i++)
    {
        for (j = 0; j < 8000; j++);
    }
}

void ADC1_Init(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    ADC_InitTypeDef ADC_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_ADC1, ENABLE);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    ADC_DeInit(ADC1);
    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_Cmd(ADC1, ENABLE);
}

uint16_t ADC1_Read(uint8_t ch)
{
    ADC_RegularChannelConfig(ADC1, ch, 1, ADC_SampleTime_55Cycles5);
    ADC_SoftwareStartConvCmd(ADC1, ENABLE);
    while (ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC) == RESET);
    return ADC_GetConversionValue(ADC1);
}

float Get_Temperature(void)
{
    uint16_t adc_val = ADC1_Read(0);
    float temp = (float)adc_val * 3.3 / 4096.0;
    temp = (temp - 0.5) * 100.0;
    return temp;
}

int main(void)
{
    USART1_Init();
    ADC1_Init();

    while (1)
    {
        if (usart_rx_len > 0)
        {
            usart_rx_buf[usart_rx_len] = '\0';
            if (strcmp((char *)usart_rx_buf, "GET_TEMP") == 0)
            {
                float temp = Get_Temperature();
                sprintf((char *)usart_tx_buf, "%.2f\r\n", temp);
                USART1_SendString((char *)usart_tx_buf);
            }
            usart_rx_len = 0;
        }
        delay_ms(100);
    }
}

这段代码的作用是：初始化串口和ADC模块，然后进入一个死循环，不断检测串口是否接收到了指定指令。如果接收到了指定指令，就采集温度值并将其发送给PC机。串口接收到的指令是以字符串的形式存储在usart_rx_buf数组中的，可以使用strcmp函数进行比较。发送温度值时，使用sprintf函数将浮点数转换成字符串，然后用USART1_SendString函数发送出去。

在PC机端，你需要使用串口助手等工具来接收并显示温度值。串口助手一般可以设置波特率、数据位、校验位等参数，需要和单片机端设置的一致。