text: #include "uart.h"
  
  void write_reg_u8(uintptr_t addr, uint8_t value)
  {
      volatile uint8_t *loc_addr = (volatile uint8_t *)addr;
      *loc_addr = value;
  }
  
  uint8_t read_reg_u8(uintptr_t addr)
  {
      return *(volatile uint8_t *)addr;
  }
  
  int is_transmit_empty()
  {
      return read_reg_u8(UART_LINE_STATUS) & 0x20;
  }
  
  void write_serial(char a)
  {
      while (is_transmit_empty() == 0) {};
  
      write_reg_u8(UART_THR, a);
  }
  
  void init_uart(uint32_t freq, uint32_t baud)
  {
      uint32_t divisor = freq / (baud << 4);
  
      write_reg_u8(UART_INTERRUPT_ENABLE, 0x00); // Disable all interrupts
      write_reg_u8(UART_LINE_CONTROL, 0x80);     // Enable DLAB (set baud rate divisor)
      write_reg_u8(UART_DLAB_LSB, divisor);         // divisor (lo byte)
      write_reg_u8(UART_DLAB_MSB, (divisor >> 8) & 0xFF);  // divisor (hi byte)
      write_reg_u8(UART_LINE_CONTROL, 0x03);     // 8 bits, no parity, one stop bit
      write_reg_u8(UART_FIFO_CONTROL, 0xC7);     // Enable FIFO, clear them, with 14-byte threshold
      write_reg_u8(UART_MODEM_CONTROL, 0x20);    // Autoflow mode
  }
  
  void print_uart(const char *str)
  {
      const char *cur = &str[0];
      while (*cur != '\0')
      {
          write_serial((uint8_t)*cur);
          ++cur;
      }
  }
  
  uint8_t bin_to_hex_table[16] = {
      '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
  
  void bin_to_hex(uint8_t inp, uint8_t res[2])
  {
      res[1] = bin_to_hex_table[inp & 0xf];
      res[0] = bin_to_hex_table[(inp >> 4) & 0xf];
      return;
  }
  
  void print_uart_int(uint32_t addr)
  {
      int i;
      for (i = 3; i > -1; i--)
      {
          uint8_t cur = (addr >> (i * 8)) & 0xff;
          uint8_t hex[2];
          bin_to_hex(cur, hex);
          write_serial(hex[0]);
          write_serial(hex[1]);
      }
  }
  
  void print_uart_addr(uint64_t addr)
  {
      int i;
      for (i = 7; i > -1; i--)
      {
          uint8_t cur = (addr >> (i * 8)) & 0xff;
          uint8_t hex[2];
          bin_to_hex(cur, hex);
          write_serial(hex[0]);
          write_serial(hex[1]);
      }
  }
  
  void print_uart_byte(uint8_t byte)
  {
      uint8_t hex[2];
      bin_to_hex(byte, hex);
      write_serial(hex[0]);
      write_serial(hex[1]);
  }
  