ensure transmission is completed
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8de6b2c199
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74819c86a2
26
lib/uart.c
26
lib/uart.c
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@ -30,31 +30,33 @@ FILE uart_io = FDEV_SETUP_STREAM((int (*)(char, struct __file *)) uart_putchar,
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/* configure serial port */
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/* configure serial port */
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void uart_init(void)
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void uart_init(void)
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{
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{
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UBRR0H = UBRRH_VALUE;
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UBRR0H = UBRRH_VALUE; // set baurate (calculated from BAUD)
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UBRR0L = UBRRL_VALUE;
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UBRR0L = UBRRL_VALUE; // set baurate (calculated from BAUD)
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#if USE_2X
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#if USE_2X
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UCSR0A |= (1<<U2X0);
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UCSR0A |= (1<<U2X0); // use double speed (set depending on BAUD)
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#else
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#else
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UCSR0A &= ~(1<<U2X0);
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UCSR0A &= ~(1<<U2X0); // do not use double speed (set depending on BAUD)
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#endif
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#endif
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UCSR0C = (1<<UCSZ01)|(1<<UCSZ00); /* 8N1 bit data */
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UCSR0C = (1<<UCSZ01)|(1<<UCSZ00); // 8N1 bit data
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UCSR0B = (1<<RXEN0)|(1<<TXEN0); /* enable RX and TX */
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UCSR0B = (1<<RXEN0)|(1<<TXEN0); // enable RX and TX
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UCSR0B |= (1<<RXCIE0); /* enable RX complete interrupt */
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UCSR0B |= (1<<RXCIE0); // enable RX complete interrupt
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}
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}
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/* put character on UART stream */
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/* put character on UART stream */
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void uart_putchar(char c, FILE *stream)
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void uart_putchar(char c, FILE *stream)
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{
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{
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if (c == '\n') {
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if (c == '\n') { // add carrier return before line feed. this is recommended for most UART terminals
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uart_putchar('\r', stream); /* add carrier return before line feed. this is recommended for most UART terminals */
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uart_putchar('\r', stream);
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}
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}
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loop_until_bit_is_set(UCSR0A, UDRE0);
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while (!(UCSR0A&(1<<UDRE0))); // wait for transmit register to empty
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UDR0 = c;
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UDR0 = c; // put data in transmit register
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while (!(UCSR0A&(1<<TXC0))); // wait for transmission to complete (else sleep mode can break it)
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UCSR0A |= (1<<TXC0); // clear transmit flag
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}
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}
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/* get character from UART stream (blocking) */
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/* get character from UART stream (blocking) */
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char uart_getchar(FILE *stream)
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char uart_getchar(FILE *stream)
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{
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{
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loop_until_bit_is_set(UCSR0A, RXC0); /* wait until data exists */
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while (!(UCSR0A&(1<<RXC0))); // wait until data exists
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return UDR0;
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return UDR0;
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}
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}
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@ -26,7 +26,7 @@ FILE uart_io;
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/* configure serial port */
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/* configure serial port */
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void uart_init(void);
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void uart_init(void);
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/* put character on UART stream */
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/* put character on UART stream (blocking) */
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void uart_putchar(char c, FILE *stream);
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void uart_putchar(char c, FILE *stream);
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/* get character from UART stream (blocking) */
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/* get character from UART stream (blocking) */
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char uart_getchar(FILE *stream);
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char uart_getchar(FILE *stream);
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