summaryrefslogtreecommitdiffstats
path: root/drivers/avr/uart.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/avr/uart.c')
-rw-r--r--drivers/avr/uart.c170
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..c6abcb6fe0
--- /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_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;
+ }
+}