mirror of
https://github.com/paparazzi/paparazzi.git
synced 2026-06-07 00:53:41 +08:00
Antoine Drouin
82 lines
1.7 KiB
C
82 lines
1.7 KiB
C
#include <avr/signal.h>
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#include <avr/interrupt.h>
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#include <avr/io.h>
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#include "uart.h"
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uint8_t uart_nb_ovrrun = 0;
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#define TX_BUF_SIZE 100
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static volatile uint8_t tx_head = TX_BUF_SIZE - 1;
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static volatile uint8_t tx_tail = TX_BUF_SIZE - 1;
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static uint8_t tx_buf[ TX_BUF_SIZE ];
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/*
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* UART Baud rate generation settings:
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*
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* With 16.0 MHz clock,UBRR=25 => 38400 baud
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* With 8.0 Mhz clock, UBRR=12 => 38400 baud
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*
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* With 4.0 MHz UBRR=12 + ub2X=1 -> 38400 baud
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*/
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void uart_init( void ) {
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/* Baudrate is 38.4k */
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UBRRH = 0;
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UBRRL = 12;
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/* double speed */
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UCSRA = _BV(U2X);
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/* Enable transmitter */
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UCSRB = _BV(TXEN);
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/* Set frame format: 8data, 1stop bit */
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UCSRC = _BV(URSEL) | _BV(UCSZ1) | _BV(UCSZ0);
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}
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static inline void load_next_byte( void ) {
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uint8_t tmp_tail;
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/* load a new byte */
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tmp_tail = tx_tail + 1;
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if( tmp_tail >= TX_BUF_SIZE )
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tmp_tail = 0;
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tx_tail = tmp_tail;
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UDR = tx_buf[tx_tail];
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}
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void uart_putc( unsigned char c ) {
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uint8_t tmp_head;
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tmp_head = tx_head + 1;
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if( tmp_head >= TX_BUF_SIZE )
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tmp_head = 0;
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/* if buffer is full do nothing */
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if( tmp_head == tx_tail ) {
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uart_nb_ovrrun++;
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return;
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}
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/* copy data to buffer */
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tx_buf[ tmp_head ] = c;
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/* update head */
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tx_head = tmp_head;
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/* if we were not allready transmitting */
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if (bit_is_clear(UCSRB, TXCIE)) {
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/* load a byte */
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load_next_byte();
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/* enable interrupt */
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sbi(UCSRB, TXCIE);
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}
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}
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SIGNAL( SIG_UART_TRANS ) {
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/* if we have nothing left to transmit */
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if( tx_head == tx_tail )
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/* disable data register empty interrupt */
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cbi(UCSRB, TXCIE);
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else
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load_next_byte();
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}
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