请给出用stm32c8t6驱动mq135初始化代码并采集PPM打印到串口，开始时使用校准模式进行校准，检测环境中的基准气体浓度，然后将其设置为参考值。确保在没有有害气体时PPM保持在400左右。

好的，以下是用stm32c8t6驱动mq135初始化代码并采集PPM打印到串口，包含校准模式的实现：

#include "stm32f1xx_hal.h"
#include <stdio.h>

#define ADC_RESOLUTION 4096.0f
#define VREF 3.3f

// MQ135相关参数，需要根据实际情况进行调整
#define RL_VALUE 20.0f
#define RO_CLEAN_AIR_FACTOR 9.83f

ADC_HandleTypeDef hadc1;
UART_HandleTypeDef huart2;

void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_USART2_UART_Init(void);
static void MX_ADC1_Init(void);

float getResistance(uint16_t raw_adc);
float getCorrectedResistance(float resistance);
float getPPM(float corrected_resistance);

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_USART2_UART_Init();
  MX_ADC1_Init();
  
  HAL_ADC_Start(&hadc1);

  // 开始校准模式
  float ro = 0;
  for (int i = 0; i < 10; i++) {
    HAL_ADC_PollForConversion(&hadc1, 100);
    uint16_t raw_adc = HAL_ADC_GetValue(&hadc1);
    float resistance = getResistance(raw_adc);
    ro += resistance / RO_CLEAN_AIR_FACTOR;
  }
  ro = ro / 10.0f;

  while (1)
  {
    HAL_ADC_PollForConversion(&hadc1, 100);
    uint16_t raw_adc = HAL_ADC_GetValue(&hadc1);

    float resistance = getResistance(raw_adc);
    float corrected_resistance = getCorrectedResistance(resistance);
    float ppm = getPPM(corrected_resistance, ro);

    // 打印PPM值到串口
    char msg[50];
    sprintf(msg, "MQ135 PPM: %.2f\r\n", ppm);
    HAL_UART_Transmit(&huart2, (uint8_t*)msg, strlen(msg), HAL_MAX_DELAY);
    
    HAL_Delay(1000);
  }
}

// 计算电阻值
float getResistance(uint16_t raw_adc)
{
  float voltage = (float)raw_adc * VREF / ADC_RESOLUTION;
  return RL_VALUE * (VREF - voltage) / voltage;
}

// 校正电阻值
float getCorrectedResistance(float resistance)
{
  return resistance / RO_CLEAN_AIR_FACTOR;
}

// 计算PPM值
float getPPM(float corrected_resistance, float ro)
{
  return pow(10, ((log10(corrected_resistance / ro) - 1.0272f) / -0.662f));
}

// 初始化GPIO
static void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
  __HAL_RCC_GPIOA_CLK_ENABLE();

  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_1, GPIO_PIN_RESET);

  GPIO_InitStruct.Pin = GPIO_PIN_1;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
}

// 初始化UART
static void MX_USART2_UART_Init(void)
{
  __HAL_RCC_USART2_CLK_ENABLE();

  huart2.Instance = USART2;
  huart2.Init.BaudRate = 115200;
  huart2.Init.WordLength = UART_WORDLENGTH_8B;
  huart2.Init.StopBits = UART_STOPBITS_1;
  huart2.Init.Parity = UART_PARITY_NONE;
  huart2.Init.Mode = UART_MODE_TX_RX;
  huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart2.Init.OverSampling = UART_OVERSAMPLING_16;
  if (HAL_UART_Init(&huart2) != HAL_OK)
  {
    Error_Handler();
  }
}

// 初始化ADC
static void MX_ADC1_Init(void)
{
  ADC_ChannelConfTypeDef sConfig = {0};

  __HAL_RCC_ADC1_CLK_ENABLE();

  hadc1.Instance = ADC1;
  hadc1.Init.ScanConvMode = DISABLE;
  hadc1.Init.ContinuousConvMode = ENABLE;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.NbrOfConversion = 1;
  if (HAL_ADC_Init(&hadc1) != HAL_OK)
  {
    Error_Handler();
  }

  sConfig.Channel = ADC_CHANNEL_0;
  sConfig.Rank = ADC_REGULAR_RANK_1;
  sConfig.SamplingTime = ADC_SAMPLETIME_239CYCLES_5;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    Error_Handler();
  }
}

void Error_Handler(void)
{
  __disable_irq();
  while (1)
  {
  }
}

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

  /** Configure the main internal regulator output voltage
  */
  __HAL_RCC_PWR_CLK_ENABLE();
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);
  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  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();
  }
  /** Initializes the CPU, AHB and APB buses clocks
  */
  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();
  }
}

需要注意的是，MQ135的基准气体浓度需要根据实际情况进行调整，因为不同的环境中基准气体浓度可能会有所不同。此外，需要根据自己的硬件连接情况进行相应的引脚配置。