usart.c

AVR单片机实现SPI通信完整源码,可直接拿过来用了

// Compiler : IAR EWAVR
// Target : M8
// Crystal: 8Mhz

//USART section
uchar   uart_ping_data[4]   =    {0x00,0x00,0x00,0x00};                       //the ping data buffer
__flash uchar   uart_pong_data[4] = {0x00,0xFF,0x00,0xFF};                    //the pong data buffer
uchar  *P_uart_data;
// UART0 initialize
// MIDI communication, the desired Baud Rate is 31.25k
// desired baud rate: 38.4k
// actual: baud rate: 28.8k (2.1%)
// char size: 8 bit
// parity: Disabled
void uart0_init(void)
{
  UCSRB = 0x00;                            //disable while setting baud rate
  UCSRA = 0x00;                            //U2X is 0, normal speed.
  UCSRC = 0xA6;                            //UCSRC anc UBRRH shares the same I/O location ,select with BIT.8(URSEL),even parity
  UBRRL = 0x0C;                            //set baud rate lo
  UBRRH = 0x00;                            //set baud rate hi
  UCSRB = 0x98;                            //receive interrupt enable ,transmit interrupt not enable
}
#pragma vector = USART_RXC_vect             //USART receive interrupt
__interrupt void USART_RXD_isr(void)
{
  uchar temp_ucsra;
  temp_ucsra = UCSRA;                       //read the flag of UCSRA
  if((temp_ucsra & 0x04) == 0x00)           //even parity pass
  {
      *P_uart_data = UDR;                   //read the receive data
      P_uart_data++;
  }
  if(P_uart_data == uart_ping_data + 4)
      P_uart_data = uart_ping_data;
}
#pragma vector = USART_TXC_vect             //USART transmit interrupt
__interrupt void USART_TXD_isr(void)
{
   //UDR = 0x66;
}
void usart_transmit(uchar *data)
{
    uchar i;
    for(i = 0; i < 33; i++)
    {
      UDR = *(data + i);
      while(!( UCSRA & (1 << UDRE)))
          ;
      UCSRA |= 0x20;
    }
}