帮我写一个单片机代码 stm32 链接 mqtt

好的，首先你需要确保你的STM32开发板已经连接上了网络，然后你需要使用MQTT协议来与服务器进行通信。这里提供一份基于STM32Cube HAL库的MQTT客户端代码，你可以根据自己的需求进行修改：

#include "main.h"
#include "stm32f1xx_hal.h"
#include "MQTTClient.h"

#define MQTT_SERVER "mqtt.server.com"
#define MQTT_PORT 1883
#define MQTT_CLIENTID "STM32Device"

char mqtt_topic[50];
char mqtt_message[50];

Network network;
MQTTClient client;
MQTTPacket_connectData connectData = MQTTPacket_connectData_initializer;

void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_USART1_UART_Init(void);

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_USART1_UART_Init();

  // 初始化MQTT网络
  NetworkInit(&network);
  NetworkConnect(&network, MQTT_SERVER, MQTT_PORT);

  // 初始化MQTT客户端
  MQTTClientInit(&client, &network, 30000, NULL, 0, NULL, 0);

  // 设置MQTT连接信息
  connectData.MQTTVersion = 4;
  connectData.clientID.cstring = MQTT_CLIENTID;
  connectData.keepAliveInterval = 60;
  connectData.cleansession = 1;

  // 连接MQTT服务器
  MQTTConnect(&client, &connectData);

  // 发布消息到MQTT服务器
  sprintf(mqtt_topic, "/stm32/device/%s/status", MQTT_CLIENTID);
  sprintf(mqtt_message, "Hello MQTT from STM32!");
  MQTTPublish(&client, mqtt_topic, strlen(mqtt_message), mqtt_message, 0, 0);

  while (1)
  {
    // 处理MQTT消息
    MQTTMessage message;
    int result = MQTTYield(&client, 1000);
    if (result != SUCCESS)
    {
      printf("MQTT error: %d\n", result);
    }
  }
}

void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_SYSCLK |
                                RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
  {
    Error_Handler();
  }
}

static void MX_USART1_UART_Init(void)
{
  huart1.Instance = USART1;
  huart1.Init.BaudRate = 115200;
  huart1.Init.WordLength = UART_WORDLENGTH_8B;
  huart1.Init.StopBits = UART_STOPBITS_1;
  huart1.Init.Parity = UART_PARITY_NONE;
  huart1.Init.Mode = UART_MODE_TX_RX;
  huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart1.Init.OverSampling = UART_OVERSAMPLING_16;
  if (HAL_UART_Init(&huart1) != HAL_OK)
  {
    Error_Handler();
  }
}

static void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};

  __HAL_RCC_GPIOC_CLK_ENABLE();

  HAL_GPIO_WritePin(GPIOC, GPIO_PIN_13, GPIO_PIN_RESET);

  GPIO_InitStruct.Pin = GPIO_PIN_13;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
}

其中，MQTT_SERVER和MQTT_PORT分别是MQTT服务器的地址和端口，MQTT_CLIENTID是你的设备ID。在示例代码中，我们向服务器发布了一条消息，然后通过MQTTYield()函数处理服务器返回的消息。

当然，在实际应用中，你需要根据自己的需求修改代码，比如订阅主题、处理消息等。希望这份代码能对你有所帮助！