130 lines
3.5 KiB
C
130 lines
3.5 KiB
C
// TODO: Teensy support(ATMega32u4/AT90USB128)
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// Fixed for Arduino Duemilanove ATmega168p by Jun Wako
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/* UART Example for Teensy USB Development Board
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* http://www.pjrc.com/teensy/
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* Copyright (c) 2009 PJRC.COM, LLC
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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// Version 1.0: Initial Release
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// Version 1.1: Add support for Teensy 2.0, minor optimizations
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include "uart.h"
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// These buffers may be any size from 2 to 256 bytes.
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#define RX_BUFFER_SIZE 64
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#define TX_BUFFER_SIZE 40
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static volatile uint8_t tx_buffer[TX_BUFFER_SIZE];
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static volatile uint8_t tx_buffer_head;
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static volatile uint8_t tx_buffer_tail;
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static volatile uint8_t rx_buffer[RX_BUFFER_SIZE];
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static volatile uint8_t rx_buffer_head;
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static volatile uint8_t rx_buffer_tail;
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// Initialize the UART
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void uart_init(uint32_t baud)
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{
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cli();
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UBRR0 = (F_CPU / 4 / baud - 1) / 2;
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UCSR0A = (1<<U2X0);
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UCSR0B = (1<<RXEN0) | (1<<TXEN0) | (1<<RXCIE0);
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UCSR0C = (1<<UCSZ01) | (1<<UCSZ00);
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tx_buffer_head = tx_buffer_tail = 0;
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rx_buffer_head = rx_buffer_tail = 0;
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sei();
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}
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// Transmit a byte
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void uart_putchar(uint8_t c)
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{
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uint8_t i;
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i = tx_buffer_head + 1;
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if (i >= TX_BUFFER_SIZE) i = 0;
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while (tx_buffer_tail == i) ; // wait until space in buffer
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//cli();
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tx_buffer[i] = c;
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tx_buffer_head = i;
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UCSR0B = (1<<RXEN0) | (1<<TXEN0) | (1<<RXCIE0) | (1<<UDRIE0);
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//sei();
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}
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// Receive a byte
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uint8_t uart_getchar(void)
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{
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uint8_t c, i;
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while (rx_buffer_head == rx_buffer_tail) ; // wait for character
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i = rx_buffer_tail + 1;
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if (i >= RX_BUFFER_SIZE) i = 0;
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c = rx_buffer[i];
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rx_buffer_tail = i;
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return c;
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}
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// Return the number of bytes waiting in the receive buffer.
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// Call this before uart_getchar() to check if it will need
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// to wait for a byte to arrive.
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uint8_t uart_available(void)
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{
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uint8_t head, tail;
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head = rx_buffer_head;
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tail = rx_buffer_tail;
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if (head >= tail) return head - tail;
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return RX_BUFFER_SIZE + head - tail;
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}
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// Transmit Interrupt
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ISR(USART_UDRE_vect)
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{
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uint8_t i;
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if (tx_buffer_head == tx_buffer_tail) {
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// buffer is empty, disable transmit interrupt
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UCSR0B = (1<<RXEN0) | (1<<TXEN0) | (1<<RXCIE0);
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} else {
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i = tx_buffer_tail + 1;
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if (i >= TX_BUFFER_SIZE) i = 0;
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UDR0 = tx_buffer[i];
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tx_buffer_tail = i;
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}
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}
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// Receive Interrupt
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ISR(USART_RX_vect)
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{
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uint8_t c, i;
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c = UDR0;
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i = rx_buffer_head + 1;
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if (i >= RX_BUFFER_SIZE) i = 0;
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if (i != rx_buffer_tail) {
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rx_buffer[i] = c;
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rx_buffer_head = i;
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}
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}
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