1 files changed, 170 insertions, 0 deletions

diff --git a/drivers/avr/uart.c b/drivers/avr/uart.c
new file mode 100644
index 000000000..e866a9e4f
--- /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;
+    }
+}