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50 lines
763 B
50 lines
763 B
10 years ago
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#include <avr/io.h>
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#include <avr/pgmspace.h>
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#include <avr/interrupt.h>
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#include "lib/meta.h"
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#include "lib/uart.h"
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//
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// This example receives asynchronously characters over UART
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// and prints them back encrypted with ROT13 cipher (the one used for
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// hints in GeoCaching)
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//
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// Echo, but with ROT13.
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ISR(USART_RX_vect)
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{
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char c = uart_rx();
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if (c == 13) {
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// print CRLF on enter
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uart_tx(10);
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uart_tx(13);
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return;
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}
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// do the ROT13
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if ((c >= 'a' && c <= 'm') || (c >= 'A' && c <= 'M')) {
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c += 13;
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} else
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if ((c >= 'n' && c <= 'z') || (c >= 'N' && c <= 'Z')) {
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c -= 13;
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}
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// Print the result
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uart_tx(c);
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}
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void main()
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{
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uart_init(9600);
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uart_isr_rx(1);
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sei();
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uart_puts_P(PSTR("ROT13 UART echo example\r\n"));
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while(1);
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}
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