protocol/serial_soft.c

   1 /*
   2 Copyright 2012 Jun WAKO <wakojun@gmail.com>
   3
   4 This software is licensed with a Modified BSD License.
   5 All of this is supposed to be Free Software, Open Source, DFSG-free,
   6 GPL-compatible, and OK to use in both free and proprietary applications.
   7 Additions and corrections to this file are welcome.
   8
   9
  10 Redistribution and use in source and binary forms, with or without
  11 modification, are permitted provided that the following conditions are met:
  12
  13 * Redistributions of source code must retain the above copyright
  14   notice, this list of conditions and the following disclaimer.
  15
  16 * Redistributions in binary form must reproduce the above copyright
  17   notice, this list of conditions and the following disclaimer in
  18   the documentation and/or other materials provided with the
  19   distribution.
  20
  21 * Neither the name of the copyright holders nor the names of
  22   contributors may be used to endorse or promote products derived
  23   from this software without specific prior written permission.
  24
  25 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  26 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  27 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  28 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  29 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  30 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  31 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  32 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  33 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  34 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  35 POSSIBILITY OF SUCH DAMAGE.
  36 */
  37
  38 #include <stdbool.h>
  39 #include <avr/io.h>
  40 #include <avr/interrupt.h>
  41 #include <util/delay.h>
  42 #include "serial.h"
  43
  44 /*
  45  *  Stupid Inefficient Busy-wait Software Serial
  46  *  is still useful for negative logic signal like Sun protocol not supported by hardware USART.
  47  */
  48
  49 #define WAIT_US     (1000000/SERIAL_BAUD)
  50
  51 void serial_init(void)
  52 {
  53     SERIAL_RXD_INIT();
  54     SERIAL_TXD_INIT();
  55 }
  56
  57 /* RX ring buffer */
  58 #define RBUF_SIZE   8
  59 static uint8_t rbuf[RBUF_SIZE];
  60 static uint8_t rbuf_head = 0;
  61 static uint8_t rbuf_tail = 0;
  62
  63
  64 uint8_t serial_recv(void)
  65 {
  66     uint8_t data = 0;
  67     if (rbuf_head == rbuf_tail) {
  68         return 0;
  69     }
  70
  71     data = rbuf[rbuf_tail];
  72     rbuf_tail = (rbuf_tail + 1) % RBUF_SIZE;
  73     return data;
  74 }
  75
  76 int16_t serial_recv2(void)
  77 {
  78     uint8_t data = 0;
  79     if (rbuf_head == rbuf_tail) {
  80         return -1;
  81     }
  82
  83     data = rbuf[rbuf_tail];
  84     rbuf_tail = (rbuf_tail + 1) % RBUF_SIZE;
  85     return data;
  86 }
  87
  88 void serial_send(uint8_t data)
  89 {
  90     /* signal state: IDLE: ON, START: OFF, STOP: ON, DATA0: OFF, DATA1: ON */
  91     /* start bit */
  92     SERIAL_TXD_OFF();
  93     _delay_us(WAIT_US);
  94
  95 #ifdef SERIAL_BIT_ORDER_MSB
  96     uint8_t mask = 0x80;
  97 #else
  98     uint8_t mask = 0x01;
  99 #endif
 100     while (mask) {
 101         if (data&mask) { SERIAL_TXD_ON(); } else { SERIAL_TXD_OFF(); }
 102         _delay_us(WAIT_US);
 103
 104 #ifdef SERIAL_BIT_ORDER_MSB
 105         mask >>= 1;
 106 #else
 107         mask <<= 1;
 108 #endif
 109     }
 110
 111     /* stop bit */
 112     SERIAL_TXD_ON();
 113     _delay_us(WAIT_US);
 114 }
 115
 116 /* detect edge of start bit */
 117 ISR(SERIAL_RXD_VECT)
 118 {
 119 PORTD ^= 1<<7;
 120     SERIAL_RXD_INT_ENTER()
 121
 122     uint8_t data = 0;
 123
 124 #ifdef SERIAL_BIT_ORDER_MSB
 125     uint8_t mask = 0x80;
 126 #else
 127     uint8_t mask = 0x01;
 128 #endif
 129
 130 #ifdef SERIAL_PARITY_ODD
 131     uint8_t parity = 0;
 132 #else
 133     uint8_t parity = 1;
 134 #endif
 135
 136     /* to center of start bit */
 137     _delay_us(WAIT_US/2);
 138 PORTD ^= 1<<7;
 139     do {
 140         /* to center of next bit */
 141         _delay_us(WAIT_US);
 142
 143 PORTD ^= 1<<7;
 144         if (SERIAL_RXD_READ()) {
 145             data |= mask;
 146             parity ^= 1;
 147         }
 148 #ifdef SERIAL_BIT_ORDER_MSB
 149         mask >>= 1;
 150 #else
 151         mask <<= 1;
 152 #endif
 153     } while (mask);
 154
 155     /* to center of parity bit */
 156     _delay_us(WAIT_US);
 157     if (SERIAL_RXD_READ()) { parity ^= 1; }
 158 PORTD ^= 1<<7;
 159
 160     /* to center of stop bit */
 161     _delay_us(WAIT_US);
 162
 163     uint8_t next = (rbuf_head + 1) % RBUF_SIZE;
 164     if (parity && next != rbuf_tail) {
 165         rbuf[rbuf_head] = data;
 166         rbuf_head = next;
 167     }
 168
 169     SERIAL_RXD_INT_EXIT();
 170 PORTD ^= 1<<7;
 171 }