protocol/ibm4704.c

   1 /*
   2 Copyright 2010,2011,2012,2013 Jun WAKO <wakojun@gmail.com>
   3 */
   4 #include <stdbool.h>
   5 #include <util/delay.h>
   6 #include "debug.h"
   7 #include "ibm4704.h"
   8
   9
  10 #define WAIT(stat, us, err) do { \
  11     if (!wait_##stat(us)) { \
  12         ibm4704_error = err; \
  13         goto ERROR; \
  14     } \
  15 } while (0)
  16
  17
  18 uint8_t ibm4704_error = 0;
  19
  20
  21 void ibm4704_init(void)
  22 {
  23     inhibit();
  24 }
  25
  26 uint8_t ibm4704_send(uint8_t data)
  27 {
  28     bool parity = true; // odd parity
  29     ibm4704_error = 0;
  30
  31     /* Request to send */
  32     idle();
  33     clock_lo();
  34
  35     /* wait for Start bit(Clock:lo/Data:hi) */
  36     WAIT(data_hi, 300, 0x30);
  37
  38     /* Data bit */
  39     for (uint8_t i = 0; i < 8; i++) {
  40         WAIT(clock_hi, 100, 0x40+i);
  41         //_delay_us(5);
  42         if (data&(1<<i)) {
  43             parity = !parity;
  44             data_hi();
  45         } else {
  46             data_lo();
  47         }
  48         WAIT(clock_lo, 100, 0x48+i);
  49     }
  50
  51     /* Parity bit */
  52     WAIT(clock_hi, 100, 0x34);
  53     if (parity) { data_hi(); } else { data_lo(); }
  54     WAIT(clock_lo, 100, 0x35);
  55
  56     /* Stop bit */
  57     WAIT(clock_hi, 100, 0x34);
  58     data_hi();
  59
  60     /* End */
  61     WAIT(data_lo, 100, 0x36);
  62
  63     inhibit();
  64     _delay_us(200); // wait to recover clock to hi
  65     return 0;
  66 ERROR:
  67     inhibit();
  68     if (ibm4704_error >= 0x30) {
  69         xprintf("x%02X ", ibm4704_error);
  70     }
  71     _delay_us(200); // wait to recover clock to hi
  72     return -1;
  73 }
  74
  75 /* receive data when host want else inhibit communication */
  76 uint8_t ibm4704_recv_response(void)
  77 {
  78     // 250 * 100us(wait start bit in ibm4704_recv)
  79     uint8_t data = 0;
  80     uint8_t try = 250;
  81     do {
  82         data = ibm4704_recv();
  83     } while (try-- && ibm4704_error);
  84     return data;
  85 }
  86
  87 /*
  88 Keyboard to Host:
  89 Clock   ~~~~___~~_~~_~~_~~_~~_~~_~~_~~_~~_~~~~~~~~ H:60us/L:30us
  90
  91 Data    ____~~X==X==X==X==X==X==X==X==X==X________
  92             |  0  1  2  3  4  5  6  7  P(odd)
  93             |  LSB                MSB
  94             Start bit(80us)
  95 */
  96 uint8_t ibm4704_recv(void)
  97 {
  98     uint8_t data = 0;
  99     bool parity = true;    // odd parity
 100     ibm4704_error = IBM4704_ERR_NONE;
 101
 102     idle();
 103     _delay_us(5);   // wait for line settles
 104
 105     /* start bit */
 106     WAIT(clock_lo, 100, 0x11); // wait for keyboard to send
 107     WAIT(data_hi, 100, 0x12);  // can be delayed that long
 108
 109     WAIT(clock_hi, 100, 0x13); // first rising edge which can take longer
 110     /* data */
 111     for (uint8_t i = 0; i < 8; i++) {
 112         WAIT(clock_hi, 100, 0x20+i);
 113         //_delay_us(5);
 114         if (data_in()) {
 115             parity = !parity;
 116             data |= (1<<i);
 117         }
 118         WAIT(clock_lo, 150, 0x28+i);
 119     }
 120
 121     /* parity */
 122     WAIT(clock_hi, 100, 0x17);
 123     if (data_in() != parity) {
 124         ibm4704_error = IBM4704_ERR_PARITY;
 125         goto ERROR;
 126     }
 127     WAIT(clock_lo, 150, 0x18);
 128
 129     /* stop bit */
 130     WAIT(clock_hi, 100, 0x19);
 131     WAIT(data_lo, 1, 0x19);
 132
 133     inhibit();
 134     _delay_us(200); // wait to recover clock to hi
 135     return data;
 136 ERROR:
 137     if (ibm4704_error > 0x12) {
 138         xprintf("x%02X ", ibm4704_error);
 139     }
 140     inhibit();
 141     _delay_us(200); // wait to recover clock to hi
 142     return -1;
 143 }