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Diffstat (limited to 'common/uart.c')
| -rw-r--r-- | common/uart.c | 129 |
1 files changed, 129 insertions, 0 deletions
diff --git a/common/uart.c b/common/uart.c new file mode 100644 index 000000000..c17649b08 --- /dev/null +++ b/common/uart.c @@ -0,0 +1,129 @@ +// TODO: Teensy support(ATMega32u4/AT90USB128) +// Fixed for Arduino Duemilanove ATmega168p by Jun Wako +/* UART Example for Teensy USB Development Board + * http://www.pjrc.com/teensy/ + * Copyright (c) 2009 PJRC.COM, LLC + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + */ + +// Version 1.0: Initial Release +// Version 1.1: Add support for Teensy 2.0, minor optimizations + + +#include <avr/io.h> +#include <avr/interrupt.h> + +#include "uart.h" + +// These buffers may be any size from 2 to 256 bytes. +#define RX_BUFFER_SIZE 64 +#define TX_BUFFER_SIZE 40 + +static volatile uint8_t tx_buffer[TX_BUFFER_SIZE]; +static volatile uint8_t tx_buffer_head; +static volatile uint8_t tx_buffer_tail; +static volatile uint8_t rx_buffer[RX_BUFFER_SIZE]; +static volatile uint8_t rx_buffer_head; +static volatile uint8_t rx_buffer_tail; + +// Initialize the UART +void uart_init(uint32_t baud) +{ + cli(); + UBRR0 = (F_CPU / 4 / baud - 1) / 2; + UCSR0A = (1<<U2X0); + UCSR0B = (1<<RXEN0) | (1<<TXEN0) | (1<<RXCIE0); + UCSR0C = (1<<UCSZ01) | (1<<UCSZ00); + tx_buffer_head = tx_buffer_tail = 0; + rx_buffer_head = rx_buffer_tail = 0; + sei(); +} + +// Transmit a byte +void uart_putchar(uint8_t c) +{ + uint8_t i; + + i = tx_buffer_head + 1; + if (i >= TX_BUFFER_SIZE) i = 0; + while (tx_buffer_tail == i) ; // wait until space in buffer + //cli(); + tx_buffer[i] = c; + tx_buffer_head = i; + UCSR0B = (1<<RXEN0) | (1<<TXEN0) | (1<<RXCIE0) | (1<<UDRIE0); + //sei(); +} + +// Receive a byte +uint8_t uart_getchar(void) +{ + uint8_t c, i; + + while (rx_buffer_head == rx_buffer_tail) ; // wait for character + i = rx_buffer_tail + 1; + if (i >= RX_BUFFER_SIZE) i = 0; + c = rx_buffer[i]; + rx_buffer_tail = i; + return c; +} + +// Return the number of bytes waiting in the receive buffer. +// Call this before uart_getchar() to check if it will need +// to wait for a byte to arrive. +uint8_t uart_available(void) +{ + uint8_t head, tail; + + head = rx_buffer_head; + tail = rx_buffer_tail; + if (head >= tail) return head - tail; + return RX_BUFFER_SIZE + head - tail; +} + +// Transmit Interrupt +ISR(USART_UDRE_vect) +{ + uint8_t i; + + if (tx_buffer_head == tx_buffer_tail) { + // buffer is empty, disable transmit interrupt + UCSR0B = (1<<RXEN0) | (1<<TXEN0) | (1<<RXCIE0); + } else { + i = tx_buffer_tail + 1; + if (i >= TX_BUFFER_SIZE) i = 0; + UDR0 = tx_buffer[i]; + tx_buffer_tail = i; + } +} + +// Receive Interrupt +ISR(USART_RX_vect) +{ + uint8_t c, i; + + c = UDR0; + i = rx_buffer_head + 1; + if (i >= RX_BUFFER_SIZE) i = 0; + if (i != rx_buffer_tail) { + rx_buffer[i] = c; + rx_buffer_head = i; + } +} + |