基于stm32单片机的简易计算器4*4矩阵键盘，只进行两个小于10的数进行运算，可用的GPIO有PE7到PE14,结果显示在串口调试助手，用言编写

好的，这个问题我可以回答。以下是基于 STM32 单片机的简易计算器 4*4 矩阵键盘的代码：

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

#define ROW_NUM 4
#define COL_NUM 4
#define BUF_SIZE 16

GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;

char buf[BUF_SIZE];
int idx = 0;

// 矩阵键盘的按键值
char keys[ROW_NUM][COL_NUM] = {
    {'1', '2', '3', '+'},
    {'4', '5', '6', '-'},
    {'7', '8', '9', '*'},
    {'C', '0', '=', '/'}
};

// 初始化GPIO口
void GPIO_Config(void)
{
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOE, ENABLE);
    
    // 初始化行
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7 | GPIO_Pin_8 | GPIO_Pin_9 | GPIO_Pin_10;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPD;
    GPIO_Init(GPIOE, &GPIO_InitStructure);
    
    // 初始化列
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11 | GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOE, &GPIO_InitStructure);
}

// 初始化串口
void USART_Config(void)
{
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
    
    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(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_ITConfig(USART1, USART_IT_TXE, ENABLE);
    USART_Cmd(USART1, ENABLE);
}

// 发送数据到串口
void USART_SendString(char *str)
{
    while (*str) {
        USART_SendData(USART1, *str++);
        while (USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET);
    }
}

// 获取按键值
char GetKeyValue(void)
{
    int i, j;
    char ch = '\0';
    
    for (i = 0; i < COL_NUM; i++) {
        GPIO_ResetBits(GPIOE, GPIO_Pin_11 << i);
        for (j = 0; j < ROW_NUM; j++) {
            if (GPIO_ReadInputDataBit(GPIOE, GPIO_Pin_7 << j) == RESET) {
                ch = keys[j][i];
                while (GPIO_ReadInputDataBit(GPIOE, GPIO_Pin_7 << j) == RESET);
            }
        }
        GPIO_SetBits(GPIOE, GPIO_Pin_11 << i);
    }
    
    return ch;
}

// 处理按键值
void HandleKeyValue(char ch)
{
    if (ch == 'C') {
        idx = 0;
        buf[idx] = '\0';
    } else if (ch == '=') {
        int num1 = buf[0] - '0';
        int num2 = buf[2] - '0';
        char op = buf[1];
        int result = 0;
        
        switch (op) {
            case '+':
                result = num1 + num2;
                break;
            case '-':
                result = num1 - num2;
                break;
            case '*':
                result = num1 * num2;
                break;
            case '/':
                result = num1 / num2;
                break;
        }
        
        sprintf(buf, "%d", result);
        idx = 0;
    } else if (ch == '+' || ch == '-' || ch == '*' || ch == '/') {
        buf[++idx] = ch;
        buf[++idx] = ' ';
    } else if (ch >= '0' && ch <= '9') {
        buf[idx] = ch;
        if (idx == 0 || idx == 2) {
            buf[++idx] = ' ';
        } else {
            idx++;
        }
    }
}

int main(void)
{
    GPIO_Config();
    USART_Config();
    
    while (1) {
        char ch = GetKeyValue();
        if (ch != '\0') {
            HandleKeyValue(ch);
            USART_SendString(buf);
        }
    }
}

void USART1_IRQHandler(void)
{
    if (USART_GetITStatus(USART1, USART_IT_TXE) != RESET) {
        USART_ClearITPendingBit(USART1, USART_IT_TXE);
    }
}

这个代码实现了基于 STM32 单片机的简易计算器 4*4 矩阵键盘，只进行两个小于10的数进行运算，可用的 GPIO 有 PE7 到 PE14，结果显示在串口调试助手。