diff options
Diffstat (limited to 'drivers/avr/uart.c')
| -rw-r--r-- | drivers/avr/uart.c | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/drivers/avr/uart.c b/drivers/avr/uart.c new file mode 100644 index 0000000000..e866a9e4f8 --- /dev/null +++ b/drivers/avr/uart.c @@ -0,0 +1,170 @@ +/* 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" + +#if defined(__AVR_ATmega16U2__) || defined(__AVR_ATmega32U2__) || defined(__AVR_ATmega16U4__) || defined(__AVR_ATmega32U4__) || defined(__AVR_AT90USB646__) || defined(__AVR_AT90USB647__) || defined(__AVR_AT90USB1286__) || defined(__AVR_AT90USB1287__) +# define UDRn UDR1 +# define UBRRnL UBRR1L +# define UCSRnA UCSR1A +# define UCSRnB UCSR1B +# define UCSRnC UCSR1C +# define U2Xn U2X1 +# define RXENn RXEN1 +# define TXENn TXEN1 +# define RXCIEn RXCIE1 +# define UCSZn1 UCSZ11 +# define UCSZn0 UCSZ10 +# define UDRIEn UDRIE1 +# define USARTn_UDRE_vect USART1_UDRE_vect +# define USARTn_RX_vect USART1_RX_vect +#elif defined(__AVR_ATmega32A__) +# define UDRn UDR +# define UBRRnL UBRRL +# define UCSRnA UCSRA +# define UCSRnB UCSRB +# define UCSRnC UCSRC +# define U2Xn U2X +# define RXENn RXEN +# define TXENn TXEN +# define RXCIEn RXCIE +# define UCSZn1 UCSZ1 +# define UCSZn0 UCSZ0 +# define UDRIEn UDRIE +# define USARTn_UDRE_vect USART_UDRE_vect +# define USARTn_RX_vect USART_RX_vect +#elif defined(__AVR_ATmega328__) || defined(__AVR_ATmega328P__) +# define UDRn UDR0 +# define UBRRnL UBRR0L +# define UCSRnA UCSR0A +# define UCSRnB UCSR0B +# define UCSRnC UCSR0C +# define U2Xn U2X0 +# define RXENn RXEN0 +# define TXENn TXEN0 +# define RXCIEn RXCIE0 +# define UCSZn1 UCSZ01 +# define UCSZn0 UCSZ00 +# define UDRIEn UDRIE0 +# define USARTn_UDRE_vect USART_UDRE_vect +# define USARTn_RX_vect USART_RX_vect +#endif + +// These buffers may be any size from 2 to 256 bytes. +#define RX_BUFFER_SIZE 64 +#define TX_BUFFER_SIZE 256 + +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(); + UBRRnL = (F_CPU / 4 / baud - 1) / 2; + UCSRnA = (1 << U2Xn); + UCSRnB = (1 << RXENn) | (1 << TXENn) | (1 << RXCIEn); + UCSRnC = (1 << UCSZn1) | (1 << UCSZn0); + 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; + // return immediately to avoid deadlock when interrupt is disabled(called from ISR) + if (tx_buffer_tail == i && (SREG & (1 << SREG_I)) == 0) return; + while (tx_buffer_tail == i) + ; // wait until space in buffer + // cli(); + tx_buffer[i] = c; + tx_buffer_head = i; + UCSRnB = (1 << RXENn) | (1 << TXENn) | (1 << RXCIEn) | (1 << UDRIEn); + // 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 whether the number of bytes waiting in the receive buffer is nonzero. +// Call this before uart_getchar() to check if it will need +// to wait for a byte to arrive. +bool uart_available(void) { + uint8_t head, tail; + + head = rx_buffer_head; + tail = rx_buffer_tail; + if (head >= tail) return (head - tail) > 0; + return (RX_BUFFER_SIZE + head - tail) > 0; +} + +// Transmit Interrupt +ISR(USARTn_UDRE_vect) { + uint8_t i; + + if (tx_buffer_head == tx_buffer_tail) { + // buffer is empty, disable transmit interrupt + UCSRnB = (1 << RXENn) | (1 << TXENn) | (1 << RXCIEn); + } else { + i = tx_buffer_tail + 1; + if (i >= TX_BUFFER_SIZE) i = 0; + UDRn = tx_buffer[i]; + tx_buffer_tail = i; + } +} + +// Receive Interrupt +ISR(USARTn_RX_vect) { + uint8_t c, i; + + c = UDRn; + 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; + } +} |