atmega128uart.txt

用于ATmega128的软件UART范例程序

#include <mega128.h>

#define RXB8 1
#define TXB8 0
#define UPE 2
#define OVR 3
#define FE 4
#define UDRE 5
#define RXC 7

#define FRAMING_ERROR (1<<FE)
#define PARITY_ERROR (1<<UPE)
#define DATA_OVERRUN (1<<OVR)
#define DATA_REGISTER_EMPTY (1<<UDRE)
#define RX_COMPLETE (1<<RXC)

// USART0 Receiver buffer
#define RX_BUFFER_SIZE0 8
char rx_buffer0[RX_BUFFER_SIZE0];
unsigned char rx_wr_index0,rx_rd_index0,rx_counter0;
// This flag is set on USART0 Receiver buffer overflow
bit rx_buffer_overflow0;

// USART0 Receiver interrupt service routine
#pragma savereg-
interrupt [USART0_RXC] void uart0_rx_isr(void)
{
char status,data;
#asm
         push r26
            push r27
            push r30
            push r31
            in   r26,sreg
            push r26
#endasm
status=UCSR0A;
data=UDR0;
if ((status & (FRAMING_ERROR | PARITY_ERROR | DATA_OVERRUN))==0)
   {
       rx_buffer0[rx_wr_index0]=data;
       if (++rx_wr_index0 == RX_BUFFER_SIZE0) rx_wr_index0=0;
       if (++rx_counter0 == RX_BUFFER_SIZE0)
          {
              rx_counter0=0;
              rx_buffer_overflow0=1;
          };
   };
#asm
       pop  r26
       out  sreg,r26
       pop  r31
       pop  r30
       pop  r27
       pop  r26
#endasm
}
#pragma savereg+

#ifndef _DEBUG_TERMINAL_IO_
// Get a character from the USART0 Receiver buffer
#define _ALTERNATE_GETCHAR_
#pragma used+
char getchar(void)
{
  char data;
  while (rx_counter0==0);
  data=rx_buffer0[rx_rd_index0];
  if (++rx_rd_index0 == RX_BUFFER_SIZE0) rx_rd_index0=0;
  #asm("cli")
    --rx_counter0;
  #asm("sei")
  return data;
}
#pragma used-
#endif

// USART0 Transmitter buffer
#define TX_BUFFER_SIZE0 8
char tx_buffer0[TX_BUFFER_SIZE0];
unsigned char tx_wr_index0,tx_rd_index0,tx_counter0;

// USART0 Transmitter interrupt service routine
#pragma savereg-
interrupt [USART0_TXC] void uart0_tx_isr(void)
{
  #asm
      push r26
      push r27
      push r30
      push r31
      in   r26,sreg
      push r26
  #edasm
  if (tx_counter0)
  {
         --tx_counter0;
       UDR0=tx_buffer0[tx_rd_index0];
       if (++tx_rd_index0 == TX_BUFFER_SIZE0) tx_rd_index0=0;
   };
  #asm
      pop  r26
      out  sreg,r26
      pop  r31
      pop  r30
      pop  r27
      pop  r26
  #endasm
}
#pragma savereg+

#ifndef _DEBUG_TERMINAL_IO_
// Write a character to the USART0 Transmitter buffer
#define _ALTERNATE_PUTCHAR_
#pragma used+
void putchar(char c)
{
  while (tx_counter0 == TX_BUFFER_SIZE0);
  #asm("cli")
   if (tx_counter0 || ((UCSR0A & DATA_REGISTER_EMPTY)==0))
   {
       tx_buffer0[tx_wr_index0]=c;
       if (++tx_wr_index0 == TX_BUFFER_SIZE0) tx_wr_index0=0;
       ++tx_counter0;
   }
   else
       UDR0=c;
  #asm("sei")
}
#pragma used-
#endif

// Standard Input/Output functions
#include <stdio.h>

// Declare your global variables here

void main(void)
{

// USART0 initialization
// Communication Parameters: 8 Data, 1 Stop, No Parity
// USART0 Receiver: On
// USART0 Transmitter: On
// USART0 Mode: Asynchronous
// USART0 Baud rate: 9600
UCSR0A=0x00;
UCSR0B=0xD8;
UCSR0C=0x06;
UBRR0H=0x00;
UBRR0L=0x67;

// Global enable interrupts
#asm("sei")

while (1)
      {
          // Place your code here

      };
}