tmk_core/common/uart.c

   1 // TODO: Teensy support(ATMega32u4/AT90USB128)
   2 // Fixed for Arduino Duemilanove ATmega168p by Jun Wako
   3 /* UART Example for Teensy USB Development Board
   4  * http://www.pjrc.com/teensy/
   5  * Copyright (c) 2009 PJRC.COM, LLC
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  20  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  23  * THE SOFTWARE.
  24  */
  25
  26 // Version 1.0: Initial Release
  27 // Version 1.1: Add support for Teensy 2.0, minor optimizations
  28
  29
  30 #include <avr/io.h>
  31 #include <avr/interrupt.h>
  32
  33 #include "uart.h"
  34
  35 // These buffers may be any size from 2 to 256 bytes.
  36 #define RX_BUFFER_SIZE 64
  37 #define TX_BUFFER_SIZE 40
  38
  39 static volatile uint8_t tx_buffer[TX_BUFFER_SIZE];
  40 static volatile uint8_t tx_buffer_head;
  41 static volatile uint8_t tx_buffer_tail;
  42 static volatile uint8_t rx_buffer[RX_BUFFER_SIZE];
  43 static volatile uint8_t rx_buffer_head;
  44 static volatile uint8_t rx_buffer_tail;
  45
  46 // Initialize the UART
  47 void uart_init(uint32_t baud)
  48 {
  49         cli();
  50         UBRR0 = (F_CPU / 4 / baud - 1) / 2;
  51         UCSR0A = (1<<U2X0);
  52         UCSR0B = (1<<RXEN0) | (1<<TXEN0) | (1<<RXCIE0);
  53         UCSR0C = (1<<UCSZ01) | (1<<UCSZ00);
  54         tx_buffer_head = tx_buffer_tail = 0;
  55         rx_buffer_head = rx_buffer_tail = 0;
  56         sei();
  57 }
  58
  59 // Transmit a byte
  60 void uart_putchar(uint8_t c)
  61 {
  62         uint8_t i;
  63
  64         i = tx_buffer_head + 1;
  65         if (i >= TX_BUFFER_SIZE) i = 0;
  66         while (tx_buffer_tail == i) ; // wait until space in buffer
  67         //cli();
  68         tx_buffer[i] = c;
  69         tx_buffer_head = i;
  70         UCSR0B = (1<<RXEN0) | (1<<TXEN0) | (1<<RXCIE0) | (1<<UDRIE0);
  71         //sei();
  72 }
  73
  74 // Receive a byte
  75 uint8_t uart_getchar(void)
  76 {
  77         uint8_t c, i;
  78
  79         while (rx_buffer_head == rx_buffer_tail) ; // wait for character
  80         i = rx_buffer_tail + 1;
  81         if (i >= RX_BUFFER_SIZE) i = 0;
  82         c = rx_buffer[i];
  83         rx_buffer_tail = i;
  84         return c;
  85 }
  86
  87 // Return the number of bytes waiting in the receive buffer.
  88 // Call this before uart_getchar() to check if it will need
  89 // to wait for a byte to arrive.
  90 uint8_t uart_available(void)
  91 {
  92         uint8_t head, tail;
  93
  94         head = rx_buffer_head;
  95         tail = rx_buffer_tail;
  96         if (head >= tail) return head - tail;
  97         return RX_BUFFER_SIZE + head - tail;
  98 }
  99
 100 // Transmit Interrupt
 101 ISR(USART_UDRE_vect)
 102 {
 103         uint8_t i;
 104
 105         if (tx_buffer_head == tx_buffer_tail) {
 106                 // buffer is empty, disable transmit interrupt
 107                 UCSR0B = (1<<RXEN0) | (1<<TXEN0) | (1<<RXCIE0);
 108         } else {
 109                 i = tx_buffer_tail + 1;
 110                 if (i >= TX_BUFFER_SIZE) i = 0;
 111                 UDR0 = tx_buffer[i];
 112                 tx_buffer_tail = i;
 113         }
 114 }
 115
 116 // Receive Interrupt
 117 ISR(USART_RX_vect)
 118 {
 119         uint8_t c, i;
 120
 121         c = UDR0;
 122         i = rx_buffer_head + 1;
 123         if (i >= RX_BUFFER_SIZE) i = 0;
 124         if (i != rx_buffer_tail) {
 125                 rx_buffer[i] = c;
 126                 rx_buffer_head = i;
 127         }
 128 }
 129