protocol/ps2_busywait.c

   1 /*
   2 Copyright 2010,2011,2012,2013 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 <util/delay.h>
  40 #include "ps2.h"
  41 #include "debug.h"
  42
  43
  44 /*
  45  * PS/2 protocol busywait version
  46  */
  47
  48 #define WAIT(stat, us, err) do { \
  49     if (!wait_##stat(us)) { \
  50         ps2_error = err; \
  51         goto ERROR; \
  52     } \
  53 } while (0)
  54
  55 uint8_t ps2_error = PS2_ERR_NONE;
  56
  57
  58 void ps2_host_init(void)
  59 {
  60     // POR(150-2000ms) plus BAT(300-500ms) may take 2.5sec([3]p.20)
  61     _delay_ms(2500);
  62
  63     inhibit();
  64 }
  65
  66 uint8_t ps2_host_send(uint8_t data)
  67 {
  68     uint8_t res = 0;
  69     bool parity = true;
  70     ps2_error = PS2_ERR_NONE;
  71     /* terminate a transmission if we have */
  72     inhibit();
  73     _delay_us(200); // at least 100us
  74
  75     /* start bit [1] */
  76     data_lo();
  77     clock_hi();
  78     WAIT(clock_lo, 20000, 10);   // may take 15ms at most until device starts clocking
  79     /* data [2-9] */
  80     for (uint8_t i = 0; i < 8; i++) {
  81         _delay_us(15);
  82         if (data&(1<<i)) {
  83             parity = !parity;
  84             data_hi();
  85         } else {
  86             data_lo();
  87         }
  88         WAIT(clock_hi, 50, 2);
  89         WAIT(clock_lo, 50, 3);
  90     }
  91     /* parity [10] */
  92     _delay_us(15);
  93     if (parity) { data_hi(); } else { data_lo(); }
  94     WAIT(clock_hi, 50, 4);
  95     WAIT(clock_lo, 50, 5);
  96     /* stop bit [11] */
  97     _delay_us(15);
  98     data_hi();
  99     /* ack [12] */
 100     WAIT(data_lo, 50, 6);
 101     WAIT(clock_lo, 50, 7);
 102
 103     /* wait for idle state */
 104     WAIT(clock_hi, 50, 8);
 105     WAIT(data_hi, 50, 9);
 106
 107     inhibit();
 108     res = ps2_host_recv_response();
 109 ERROR:
 110     inhibit();
 111     return res;
 112 }
 113
 114 /* receive data when host want else inhibit communication */
 115 uint8_t ps2_host_recv_response(void)
 116 {
 117     // Command might take 20ms to response([3]p.21)
 118     // TrackPoint might take 25ms ([5]2.7)
 119     // 250 * 100us(wait for start bit in ps2_host_recv)
 120     uint8_t data = 0;
 121     uint8_t try = 250;
 122     do {
 123         data = ps2_host_recv();
 124     } while (try-- && ps2_error);
 125     return data;
 126 }
 127
 128 /* send LED state to keyboard */
 129 void ps2_host_set_led(uint8_t led)
 130 {
 131     ps2_host_send(0xED);
 132     ps2_host_send(led);
 133 }
 134
 135
 136 /* called after start bit comes */
 137 uint8_t ps2_host_recv(void)
 138 {
 139     uint8_t data = 0;
 140     bool parity = true;
 141     ps2_error = PS2_ERR_NONE;
 142
 143     /* release lines(idle state) */
 144     idle();
 145
 146     /* start bit [1] */
 147     WAIT(clock_lo, 100, 1); // TODO: this is enough?
 148     WAIT(data_lo, 1, 2);
 149     WAIT(clock_hi, 50, 3);
 150
 151     /* data [2-9] */
 152     for (uint8_t i = 0; i < 8; i++) {
 153         WAIT(clock_lo, 50, 4);
 154         if (data_in()) {
 155             parity = !parity;
 156             data |= (1<<i);
 157         }
 158         WAIT(clock_hi, 50, 5);
 159     }
 160
 161     /* parity [10] */
 162     WAIT(clock_lo, 50, 6);
 163     if (data_in() != parity) {
 164         ps2_error = PS2_ERR_PARITY;
 165         goto ERROR;
 166     }
 167     WAIT(clock_hi, 50, 7);
 168
 169     /* stop bit [11] */
 170     WAIT(clock_lo, 50, 8);
 171     WAIT(data_hi, 1, 9);
 172     WAIT(clock_hi, 50, 10);
 173
 174     inhibit();
 175     return data;
 176 ERROR:
 177     if (ps2_error > PS2_ERR_STARTBIT3) {
 178         xprintf("x%02X\n", ps2_error);
 179     }
 180     inhibit();
 181     return 0;
 182 }