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 #if 1
  52 #define WAIT_TICK     (1000000/SERIAL_BAUD)
  53 #define WAIT4(tick) _delay_us(tick)
  54 #else
  55 #define WAIT_TICK   ((16000000/SERIAL_BAUD)/4 - 5)
  56 static inline void  WAIT4(uint8_t tick)
  57 {
  58         __asm__ __volatile__ (
  59                 "1: dec %0" "\n\t"
  60                 "nop"       "\n\t"
  61                 "brne 1b"
  62                 :
  63                 : "r" (tick)
  64         );
  65 }
  66 #endif
  67
  68 void serial_init(void)
  69 {
  70     SERIAL_RXD_INIT();
  71     SERIAL_TXD_INIT();
  72 }
  73
  74 /* RX ring buffer */
  75 #define RBUF_SIZE   8
  76 static uint8_t rbuf[RBUF_SIZE];
  77 static uint8_t rbuf_head = 0;
  78 static uint8_t rbuf_tail = 0;
  79
  80
  81 uint8_t serial_recv(void)
  82 {
  83     uint8_t data = 0;
  84     if (rbuf_head == rbuf_tail) {
  85         return 0;
  86     }
  87
  88     data = rbuf[rbuf_tail];
  89     rbuf_tail = (rbuf_tail + 1) % RBUF_SIZE;
  90     return data;
  91 }
  92
  93 void serial_send(uint8_t data)
  94 {
  95     /* signal state: IDLE: ON, START: OFF, STOP: ON, DATA0: OFF, DATA1: ON */
  96     /* start bit */
  97     SERIAL_TXD_OFF();
  98     _delay_us(WAIT_US);
  99
 100 #ifdef SERIAL_BIT_ORDER_MSB
 101     uint8_t mask = 0x80;
 102 #else
 103     uint8_t mask = 0x01;
 104 #endif
 105     while (mask) {
 106         if (data&mask) { SERIAL_TXD_ON(); } else { SERIAL_TXD_OFF(); }
 107         _delay_us(WAIT_US);
 108
 109 #ifdef SERIAL_BIT_ORDER_MSB
 110         mask >>= 1;
 111 #else
 112         mask <<= 1;
 113 #endif
 114     }
 115
 116     /* stop bit */
 117     SERIAL_TXD_ON();
 118     _delay_us(WAIT_US);
 119 }
 120
 121 /* detect edge of start bit */
 122 ISR(SERIAL_RXD_VECT)
 123 {
 124 PORTD ^= 1<<7;
 125     SERIAL_RXD_INT_ENTER()
 126
 127     uint8_t data = 0;
 128
 129 #ifdef SERIAL_BIT_ORDER_MSB
 130     uint8_t mask = 0x80;
 131 #else
 132     uint8_t mask = 0x01;
 133 #endif
 134
 135 #ifdef SERIAL_PARITY_ODD
 136     uint8_t parity = 0;
 137 #else
 138     uint8_t parity = 1;
 139 #endif
 140
 141     /* to center of start bit */
 142     //_delay_us(WAIT_US/2);
 143     WAIT4(WAIT_TICK/2);
 144 PORTD ^= 1<<7;
 145     do {
 146         /* to center of next bit */
 147         //_delay_us(WAIT_US);
 148         WAIT4(WAIT_TICK);
 149
 150 PORTD ^= 1<<7;
 151         if (SERIAL_RXD_READ()) {
 152             data |= mask;
 153             parity ^= 1;
 154         }
 155 #ifdef SERIAL_BIT_ORDER_MSB
 156         mask >>= 1;
 157 #else
 158         mask <<= 1;
 159 #endif
 160     } while (mask);
 161
 162     /* to center of parity bit */
 163     //_delay_us(WAIT_US);
 164     WAIT4(WAIT_TICK);
 165     if (SERIAL_RXD_READ()) { parity ^= 1; }
 166 PORTD ^= 1<<7;
 167
 168     /* to center of stop bit */
 169     //_delay_us(WAIT_US);
 170     WAIT4(WAIT_TICK);
 171
 172     uint8_t next = (rbuf_head + 1) % RBUF_SIZE;
 173     //if (parity && next != rbuf_tail) {
 174     if (next != rbuf_tail) {
 175         rbuf[rbuf_head] = data;
 176         rbuf_head = next;
 177     }
 178
 179     SERIAL_RXD_INT_EXIT();
 180 PORTD ^= 1<<7;
 181 }