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     // POR
  24     //_delay_ms(2500);
  25     //while ( 0xA3 != ibm4704_recv() ) ;
  26
  27     inhibit();
  28     DDRD |= 1<<3;
  29     PORTD &= ~(1<<3);
  30 }
  31
  32 uint8_t ibm4704_send(uint8_t data)
  33 {
  34     bool parity = true; // odd parity
  35     ibm4704_error = 0;
  36
  37     /* Request to send */
  38     idle();
  39     clock_lo();
  40 PIND |= 1<<3;
  41
  42     /* wait for Start bit(Clock:lo/Data:hi) */
  43     WAIT(data_hi, 300, 0x30);
  44
  45     /* Data bit */
  46     for (uint8_t i = 0; i < 8; i++) {
  47         WAIT(clock_hi, 100, 0x31);
  48         //_delay_us(5);
  49 PIND |= 1<<3;
  50         if (data&(1<<i)) {
  51             parity = !parity;
  52             data_hi();
  53         } else {
  54             data_lo();
  55         }
  56         WAIT(clock_lo, 100, 0x32);
  57     }
  58
  59     /* Parity bit */
  60     WAIT(clock_hi, 100, 4);
  61 PIND |= 1<<3;
  62     if (parity) { data_hi(); } else { data_lo(); }
  63     WAIT(clock_lo, 100, 5);
  64
  65     /* Stop bit */
  66     WAIT(clock_hi, 100, 4);
  67     data_hi();
  68
  69     /* End */
  70     WAIT(data_lo, 100, 6);
  71
  72     inhibit();
  73     _delay_us(200); // wait to recover clock to hi
  74     return 0;
  75 ERROR:
  76     inhibit();
  77 xprintf("x%02X ", ibm4704_error);
  78     _delay_us(200); // wait to recover clock to hi
  79     return -1;
  80 }
  81
  82 /* receive data when host want else inhibit communication */
  83 uint8_t ibm4704_recv_response(void)
  84 {
  85     // 250 * 100us(wait start bit in ibm4704_recv)
  86     uint8_t data = 0;
  87     uint8_t try = 250;
  88     do {
  89         data = ibm4704_recv();
  90     } while (try-- && ibm4704_error);
  91     return data;
  92 }
  93
  94 /*
  95 Keyboard to Host:
  96 Clock   ~~~~___~~_~~_~~_~~_~~_~~_~~_~~_~~_~~~~~~~~ H:60us/L:30us
  97
  98 Data    ____~~X==X==X==X==X==X==X==X==X==X________
  99             |  0  1  2  3  4  5  6  7  P(odd)
 100             |  LSB                MSB
 101             Start bit(80us)
 102 */
 103 uint8_t ibm4704_recv(void)
 104 {
 105     uint8_t data = 0;
 106     bool parity = true;    // odd parity
 107     ibm4704_error = IBM4704_ERR_NONE;
 108
 109     idle();
 110     _delay_us(5);   // wait for line settles
 111
 112     /* start bit */
 113     WAIT(clock_lo, 100, 1); // wait for keyboard to send
 114     WAIT(data_hi, 100, 2);  // can be delayed that long
 115
 116     WAIT(clock_hi, 100, 3); // first rising edge which can take longer
 117     /* data */
 118     for (uint8_t i = 0; i < 8; i++) {
 119         WAIT(clock_hi, 100, 0x20+i);
 120         //_delay_us(5);
 121         if (data_in()) {
 122             parity = !parity;
 123             data |= (1<<i);
 124         }
 125         WAIT(clock_lo, 150, 0x28+i);
 126     }
 127
 128     /* parity */
 129     WAIT(clock_hi, 100, 7);
 130     if (data_in() != parity) {
 131         ibm4704_error = IBM4704_ERR_PARITY;
 132         goto ERROR;
 133     }
 134     WAIT(clock_lo, 150, 8);
 135
 136     /* stop bit */
 137     WAIT(clock_hi, 100, 9);
 138     WAIT(data_lo, 1, 9);
 139
 140     inhibit();
 141     _delay_us(200); // wait to recover clock to hi
 142     return data;
 143 ERROR:
 144     if (ibm4704_error > 2) {
 145         xprintf("x%02X ", ibm4704_error);
 146     }
 147     inhibit();
 148     _delay_us(200); // wait to recover clock to hi
 149     return -1;
 150 }