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     (1000000L/SERIAL_BAUD)
  50
  51 /* debug for signal timing, see debug pin with oscilloscope */
  52 #ifdef SERIAL_SOFT_DEBUG
  53     #define SERIAL_SOFT_DEBUG_INIT()    (DDRD |= 1<<7)
  54     #define SERIAL_SOFT_DEBUG_TGL()     (PORTD ^= 1<<7)
  55 #else
  56     #define SERIAL_SOFT_DEBUG_INIT()
  57     #define SERIAL_SOFT_DEBUG_TGL()
  58 #endif
  59
  60
  61 void serial_init(void)
  62 {
  63     SERIAL_SOFT_DEBUG_INIT();
  64
  65     SERIAL_RXD_INIT();
  66     SERIAL_TXD_INIT();
  67 }
  68
  69 /* RX ring buffer */
  70 #define RBUF_SIZE   8
  71 static uint8_t rbuf[RBUF_SIZE];
  72 static uint8_t rbuf_head = 0;
  73 static uint8_t rbuf_tail = 0;
  74
  75
  76 uint8_t serial_recv(void)
  77 {
  78     uint8_t data = 0;
  79     if (rbuf_head == rbuf_tail) {
  80         return 0;
  81     }
  82
  83     data = rbuf[rbuf_tail];
  84     rbuf_tail = (rbuf_tail + 1) % RBUF_SIZE;
  85     return data;
  86 }
  87
  88 int16_t serial_recv2(void)
  89 {
  90     uint8_t data = 0;
  91     if (rbuf_head == rbuf_tail) {
  92         return -1;
  93     }
  94
  95     data = rbuf[rbuf_tail];
  96     rbuf_tail = (rbuf_tail + 1) % RBUF_SIZE;
  97     return data;
  98 }
  99
 100 void serial_send(uint8_t data)
 101 {
 102     /* signal state: IDLE: ON, START: OFF, STOP: ON, DATA0: OFF, DATA1: ON */
 103
 104 #ifdef SERIAL_BIT_ORDER_MSB
 105     uint8_t mask = 0x80;
 106 #else
 107     uint8_t mask = 0x01;
 108 #endif
 109
 110 #ifdef SERIAL_PARITY_ODD
 111     uint8_t parity = 1;
 112 #elif defined(SERIAL_PARITY_EVEN)
 113     uint8_t parity = 0;
 114 #endif
 115
 116     /* start bit */
 117     SERIAL_TXD_OFF();
 118     _delay_us(WAIT_US-2);
 119
 120     while (mask) {
 121         if (data&mask) {
 122             SERIAL_TXD_ON();
 123 #if defined(SERIAL_PARITY_EVEN) || defined(SERIAL_PARITY_ODD)
 124             parity ^= 1;
 125 #endif
 126         } else {
 127             SERIAL_TXD_OFF();
 128         }
 129         _delay_us(WAIT_US-2);
 130
 131 #ifdef SERIAL_BIT_ORDER_MSB
 132         mask >>= 1;
 133 #else
 134         mask <<= 1;
 135 #endif
 136     }
 137
 138 #if defined(SERIAL_PARITY_EVEN) || defined(SERIAL_PARITY_ODD)
 139     /* to center of parity bit */
 140     if (parity) {
 141         SERIAL_TXD_ON();
 142     } else {
 143         SERIAL_TXD_OFF();
 144     }
 145     _delay_us(WAIT_US-2);
 146 #endif
 147
 148     /* stop bit */
 149     SERIAL_TXD_ON();
 150     _delay_us(WAIT_US-2);
 151 }
 152
 153 /* detect edge of start bit */
 154 ISR(SERIAL_RXD_VECT)
 155 {
 156     SERIAL_SOFT_DEBUG_TGL()
 157     SERIAL_RXD_INT_ENTER()
 158
 159     uint8_t data = 0;
 160
 161 #ifdef SERIAL_BIT_ORDER_MSB
 162     uint8_t mask = 0x80;
 163 #else
 164     uint8_t mask = 0x01;
 165 #endif
 166
 167 #ifdef SERIAL_PARITY_ODD
 168     uint8_t parity = 0;
 169 #elif defined(SERIAL_PARITY_EVEN)
 170     uint8_t parity = 1;
 171 #endif
 172
 173     /* to center of start bit */
 174     _delay_us(WAIT_US/2);
 175     SERIAL_SOFT_DEBUG_TGL()
 176     do {
 177         /* to center of next bit */
 178         _delay_us(WAIT_US);
 179
 180     SERIAL_SOFT_DEBUG_TGL()
 181         if (SERIAL_RXD_READ()) {
 182             data |= mask;
 183 #if defined(SERIAL_PARITY_EVEN) || defined(SERIAL_PARITY_ODD)
 184             parity ^= 1;
 185 #endif
 186         }
 187 #ifdef SERIAL_BIT_ORDER_MSB
 188         mask >>= 1;
 189 #else
 190         mask <<= 1;
 191 #endif
 192     } while (mask);
 193
 194 #if defined(SERIAL_PARITY_EVEN) || defined(SERIAL_PARITY_ODD)
 195     /* to center of parity bit */
 196     _delay_us(WAIT_US);
 197     if (SERIAL_RXD_READ()) { parity ^= 1; }
 198     SERIAL_SOFT_DEBUG_TGL()
 199 #endif
 200
 201     /* to center of stop bit */
 202     _delay_us(WAIT_US);
 203
 204     uint8_t next = (rbuf_head + 1) % RBUF_SIZE;
 205 #if defined(SERIAL_PARITY_EVEN) || defined(SERIAL_PARITY_ODD)
 206     if (parity && next != rbuf_tail) {
 207 #else
 208     if (next != rbuf_tail) {
 209 #endif
 210         rbuf[rbuf_head] = data;
 211         rbuf_head = next;
 212     }
 213
 214     SERIAL_RXD_INT_EXIT();
 215     SERIAL_SOFT_DEBUG_TGL()
 216 }