stm32hal库显示字符的例子，例如

如何在OLED屏幕上显示字符？

您好，下面是一个示例代码，使用STM32HAL库在OLED屏幕上显示字符。

首先，需要定义一些参数来设置OLED屏幕的尺寸和I2C通信接口：

#define OLED_WIDTH 128
#define OLED_HEIGHT 32

#define SSD1306_I2C_ADDR 0x3C

I2C_HandleTypeDef hi2c1;

然后，需要调用以下函数初始化I2C接口：

void MX_I2C1_Init(void)
{
  hi2c1.Instance = I2C1;
  hi2c1.Init.ClockSpeed = 400000;
  hi2c1.Init.DutyCycle = I2C_DUTYCYCLE_2;
  hi2c1.Init.OwnAddress1 = 0;
  hi2c1.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
  hi2c1.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
  hi2c1.Init.OwnAddress2 = 0;
  hi2c1.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
  hi2c1.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;
  if (HAL_I2C_Init(&hi2c1) != HAL_OK)
  {
    Error_Handler();
  }
}

接着，需要调用以下函数初始化OLED屏幕：

void ssd1306_init()
{
  uint8_t init_cmds[] = {
      0xAE, //display off
      0xD5, //display divide ratio/osc. freq. mode
      0x80, //divide ratio=1, osc. freq.=0
      0xA8, //multiplex mode
      OLED_HEIGHT - 1, //multiplex ratio
      0xD3, //display offset
      0x0, //offset=0
      0x40, //start line
      0x8D, //charge pump
      0x14, //enable charge pump
      0x20, //memory addressing mode
      0x00, //horizontal addressing mode
      0x21, //column address
      0x00, //start column
      OLED_WIDTH - 1, //end column
      0x22, //page address
      0x00, //start page
      OLED_HEIGHT / 8 - 1, //end page
      0xA4, //display on, no A5 inversion
      0x40, //set display start line
      0xAF, //display on
  };

  HAL_I2C_Mem_Write(&hi2c1, SSD1306_I2C_ADDR, 0x00, 1, init_cmds, sizeof(init_cmds));
}

最后，可以调用以下代码在OLED屏幕上显示字符：

void ssd1306_display_char(uint8_t x, uint8_t y, char c)
{
  assert(x < OLED_WIDTH);
  assert(y < OLED_HEIGHT);

  const uint8_t* glyph = font_table[(c - 32) * 8];
  uint8_t page = y / 8;
  uint8_t pixel_row = y % 8;

  uint8_t data[8];

  for (int i = 0; i < 8; i++) {
    uint8_t row_data = glyph[i];
    if (pixel_row != 0) {
      row_data <<= pixel_row;
      row_data |= glyph[i+1] >> (8 - pixel_row);
    }
    data[i] = row_data;
  }

  uint8_t cmd[] = {
      0x00 | (x & 0x0F), //set lower column address
      0x10 | ((x >> 4) & 0x0F), //set higher column address
      0xB0 | page, //set page address
  };

  HAL_I2C_Mem_Write(&hi2c1, SSD1306_I2C_ADDR, 0x00, 1, cmd, sizeof(cmd));
  HAL_I2C_Mem_Write(&hi2c1, SSD1306_I2C_ADDR, 0x40, 1, data, sizeof(data));
}

其中，font_table是一个包含字符字形数据的表格，可以通过转换TrueType字体文件生成。该例子中使用的是7x8像素大小的ASCII字体。

希望这能回答您的问题，如果还有疑问，请随时问我。