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 /* 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     /* start bit */
 104     SERIAL_TXD_OFF();
 105     _delay_us(WAIT_US);
 106
 107 #ifdef SERIAL_BIT_ORDER_MSB
 108     uint8_t mask = 0x80;
 109 #else
 110     uint8_t mask = 0x01;
 111 #endif
 112     while (mask) {
 113         if (data&mask) { SERIAL_TXD_ON(); } else { SERIAL_TXD_OFF(); }
 114         _delay_us(WAIT_US);
 115
 116 #ifdef SERIAL_BIT_ORDER_MSB
 117         mask >>= 1;
 118 #else
 119         mask <<= 1;
 120 #endif
 121     }
 122
 123     /* stop bit */
 124     SERIAL_TXD_ON();
 125     _delay_us(WAIT_US);
 126 }
 127
 128 /* detect edge of start bit */
 129 ISR(SERIAL_RXD_VECT)
 130 {
 131     SERIAL_SOFT_DEBUG_TGL()
 132     SERIAL_RXD_INT_ENTER()
 133
 134     uint8_t data = 0;
 135
 136 #ifdef SERIAL_BIT_ORDER_MSB
 137     uint8_t mask = 0x80;
 138 #else
 139     uint8_t mask = 0x01;
 140 #endif
 141
 142 #ifdef SERIAL_PARITY_ODD
 143     uint8_t parity = 0;
 144 #elif defined(SERIAL_PARITY_EVEN)
 145     uint8_t parity = 1;
 146 #endif
 147
 148     /* to center of start bit */
 149     _delay_us(WAIT_US/2);
 150     SERIAL_SOFT_DEBUG_TGL()
 151     do {
 152         /* to center of next bit */
 153         _delay_us(WAIT_US);
 154
 155     SERIAL_SOFT_DEBUG_TGL()
 156         if (SERIAL_RXD_READ()) {
 157             data |= mask;
 158 #if defined(SERIAL_PARITY_EVEN) || defined(SERIAL_PARITY_ODD)
 159             parity ^= 1;
 160 #endif
 161         }
 162 #ifdef SERIAL_BIT_ORDER_MSB
 163         mask >>= 1;
 164 #else
 165         mask <<= 1;
 166 #endif
 167     } while (mask);
 168
 169 #if defined(SERIAL_PARITY_EVEN) || defined(SERIAL_PARITY_ODD)
 170     /* to center of parity bit */
 171     _delay_us(WAIT_US);
 172     if (SERIAL_RXD_READ()) { parity ^= 1; }
 173     SERIAL_SOFT_DEBUG_TGL()
 174 #endif
 175
 176     /* to center of stop bit */
 177     _delay_us(WAIT_US);
 178
 179     uint8_t next = (rbuf_head + 1) % RBUF_SIZE;
 180 #if defined(SERIAL_PARITY_EVEN) || defined(SERIAL_PARITY_ODD)
 181     if (parity && next != rbuf_tail) {
 182 #else
 183     if (next != rbuf_tail) {
 184 #endif
 185         rbuf[rbuf_head] = data;
 186         rbuf_head = next;
 187     }
 188
 189     SERIAL_RXD_INT_EXIT();
 190     SERIAL_SOFT_DEBUG_TGL()
 191 }