帮我设计一个stm32f103标准库程序使其可以接收来自python串口通信的字符，并根据接受的字符控制两个级联MAX7219led点阵显示上箭头下箭头左箭头右箭头四种不同的表情，在未接收到时显示问号的表情，我需要完整的代码

好的，下面是我为您编写的代码：

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

#define MAX7219_REG_NOOP        0x00
#define MAX7219_REG_DIGIT0      0x01
#define MAX7219_REG_DIGIT1      0x02
#define MAX7219_REG_DIGIT2      0x03
#define MAX7219_REG_DIGIT3      0x04
#define MAX7219_REG_DIGIT4      0x05
#define MAX7219_REG_DIGIT5      0x06
#define MAX7219_REG_DIGIT6      0x07
#define MAX7219_REG_DIGIT7      0x08
#define MAX7219_REG_DECODEMODE  0x09
#define MAX7219_REG_INTENSITY   0x0A
#define MAX7219_REG_SCANLIMIT   0x0B
#define MAX7219_REG_SHUTDOWN    0x0C
#define MAX7219_REG_DISPLAYTEST 0x0F

#define LED_NOOP        0x00
#define LED_CLEAR_ALL   0x01
#define LED_UP          0x02
#define LED_DOWN        0x03
#define LED_LEFT        0x04
#define LED_RIGHT       0x05
#define LED_QUESTION    0x06

void USART1_Init(void);
void USART_SendString(USART_TypeDef* USARTx, char* s);
void MAX7219_Send(uint8_t address, uint8_t data);
void MAX7219_Init(void);
void LED_Show(uint8_t led_type);

int main(void)
{
    USART1_Init();
    MAX7219_Init();
    char c;
    while (1)
    {
        if (USART_GetFlagStatus(USART1, USART_FLAG_RXNE) != RESET)
        {
            c = USART_ReceiveData(USART1);
            switch (c)
            {
                case 'U':
                case 'u':
                    LED_Show(LED_UP);
                    break;
                case 'D':
                case 'd':
                    LED_Show(LED_DOWN);
                    break;
                case 'L':
                case 'l':
                    LED_Show(LED_LEFT);
                    break;
                case 'R':
                case 'r':
                    LED_Show(LED_RIGHT);
                    break;
                default:
                    LED_Show(LED_QUESTION);
                    break;
            }
        }
    }
}

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

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_USART1, ENABLE);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    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);

    USART_Cmd(USART1, ENABLE);
}

void USART_SendString(USART_TypeDef* USARTx, char* s)
{
    while (*s)
    {
        while (USART_GetFlagStatus(USARTx, USART_FLAG_TXE) == RESET);
        USART_SendData(USARTx, *s++);
    }
}

void MAX7219_Send(uint8_t address, uint8_t data)
{
    GPIO_ResetBits(GPIOB, GPIO_Pin_12);
    for (int i = 0; i < 8; i++)
    {
        GPIO_WriteBit(GPIOB, GPIO_Pin_13, (BitAction)((address >> (7 - i)) & 0x01));
        GPIO_WriteBit(GPIOB, GPIO_Pin_15, (BitAction)((data >> (7 - i)) & 0x01));
        GPIO_SetBits(GPIOB, GPIO_Pin_14);
        GPIO_ResetBits(GPIOB, GPIO_Pin_14);
    }
    GPIO_SetBits(GPIOB, GPIO_Pin_12);
}

void MAX7219_Init(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_Init(GPIOB, &GPIO_InitStructure);

    MAX7219_Send(MAX7219_REG_SCANLIMIT, 0x07);
    MAX7219_Send(MAX7219_REG_DECODEMODE, 0x00);
    MAX7219_Send(MAX7219_REG_DISPLAYTEST, 0x00);
    MAX7219_Send(MAX7219_REG_SHUTDOWN, 0x01);
    MAX7219_Send(MAX7219_REG_INTENSITY, 0x0F);
    MAX7219_Send(MAX7219_REG_CLEAR_ALL, 0x00);
}

void LED_Show(uint8_t led_type)
{
    switch (led_type)
    {
        case LED_CLEAR_ALL:
            MAX7219_Send(MAX7219_REG_DIGIT0, 0);
            MAX7219_Send(MAX7219_REG_DIGIT1, 0);
            MAX7219_Send(MAX7219_REG_DIGIT2, 0);
            MAX7219_Send(MAX7219_REG_DIGIT3, 0);
            MAX7219_Send(MAX7219_REG_DIGIT4, 0);
            MAX7219_Send(MAX7219_REG_DIGIT5, 0);
            MAX7219_Send(MAX7219_REG_DIGIT6, 0);
            MAX7219_Send(MAX7219_REG_DIGIT7, 0);
            break;
        case LED_UP:
            MAX7219_Send(MAX7219_REG_DIGIT0, 0x18);
            MAX7219_Send(MAX7219_REG_DIGIT1, 0x3C);
            MAX7219_Send(MAX7219_REG_DIGIT2, 0x7E);
            MAX7219_Send(MAX7219_REG_DIGIT3, 0xFF);
            MAX7219_Send(MAX7219_REG_DIGIT4, 0xFF);
            MAX7219_Send(MAX7219_REG_DIGIT5, 0x7E);
            MAX7219_Send(MAX7219_REG_DIGIT6, 0x3C);
            MAX7219_Send(MAX7219_REG_DIGIT7, 0x18);
            break;
        case LED_DOWN:
            MAX7219_Send(MAX7219_REG_DIGIT0, 0x18);
            MAX7219_Send(MAX7219_REG_DIGIT1, 0x3C);
            MAX7219_Send(MAX7219_REG_DIGIT2, 0x7E);
            MAX7219_Send(MAX7219_REG_DIGIT3, 0xFF);
            MAX7219_Send(MAX7219_REG_DIGIT4, 0xFF);
            MAX7219_Send(MAX7219_REG_DIGIT5, 0x7E);
            MAX7219_Send(MAX7219_REG_DIGIT6, 0x3C);
            MAX7219_Send(MAX7219_REG_DIGIT7, 0x18);
            break;
        case LED_LEFT:
            MAX7219_Send(MAX7219_REG_DIGIT0, 0x18);
            MAX7219_Send(MAX7219_REG_DIGIT1, 0x3C);
            MAX7219_Send(MAX7219_REG_DIGIT2, 0x7E);
            MAX7219_Send(MAX7219_REG_DIGIT3, 0xFF);
            MAX7219_Send(MAX7219_REG_DIGIT4, 0x7E);
            MAX7219_Send(MAX7219_REG_DIGIT5, 0x3C);
            MAX7219_Send(MAX7219_REG_DIGIT6, 0x18);
            MAX7219_Send(MAX7219_REG_DIGIT7, 0x00);
            break;
        case LED_RIGHT:
            MAX7219_Send(MAX7219_REG_DIGIT0, 0x00);
            MAX7219_Send(MAX7219_REG_DIGIT1, 0x18);
            MAX7219_Send(MAX7219_REG_DIGIT2, 0x3C);
            MAX7219_Send(MAX7219_REG_DIGIT3, 0x7E);
            MAX7219_Send(MAX7219_REG_DIGIT4, 0xFF);
            MAX7219_Send(MAX7219_REG_DIGIT5, 0x7E);
            MAX7219_Send(MAX7219_REG_DIGIT6, 0x3C);
            MAX7219_Send(MAX7219_REG_DIGIT7, 0x18);
            break;
        case LED_QUESTION:
            MAX7219_Send(MAX7219_REG_DIGIT0, 0x3C);
            MAX7219_Send(MAX7219_REG_DIGIT1, 0x42);
            MAX7219_Send(MAX7219_REG_DIGIT2, 0x40);
            MAX7219_Send(MAX7219_REG_DIGIT3, 0x3C);
            MAX7219_Send(MAX7219_REG_DIGIT4, 0x04);
            MAX7219_Send(MAX7219_REG_DIGIT5, 0x08);
            MAX7219_Send(MAX7219_REG_DIGIT6, 0x10);
            MAX7219_Send(MAX7219_REG_DIGIT7, 0x1F);
            break;
        default:
            break;
    }
}

这份代码实现了串口接收并根据接收到的字符控制MAX7219点阵LED显示不同的图案。其中，USART1_Init()函数初始化了USART1串口通信，MAX7219_Init()函数初始化了MAX7219点阵LED显示模块，LED_Show()函数根据输入的参数控制LED显示不同的图案。

在这份代码中，我们假设您将MAX7219点阵LED模块的VCC、GND、DIN、CS、CLK引脚分别连接到了STM32F103的5V、GND、PA7、PB12、PB13上。另外，我们也假设您将串口通信的TX、RX引脚分别连接到了STM32F103的PA9、PA10上。

希望这份代码对您有所帮助！