diff options
Diffstat (limited to 'platforms/avr/drivers/uart.c')
| -rw-r--r-- | platforms/avr/drivers/uart.c | 170 | 
1 files changed, 170 insertions, 0 deletions
| diff --git a/platforms/avr/drivers/uart.c b/platforms/avr/drivers/uart.c new file mode 100644 index 0000000000..c6abcb6fe0 --- /dev/null +++ b/platforms/avr/drivers/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_AT90USB162__) || 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; +    } +} | 
