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 /*
  27 Host to Keyboard
  28 ----------------
  29 Data bits are LSB first and Parity is odd. Clock has around 60us high and 30us low part.
  30
  31         ____        __   __   __   __   __   __   __   __   __   ________
  32 Clock       \______/  \_/  \_/  \_/  \_/  \_/  \_/  \_/  \_/  \_/
  33             ^   ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ___
  34 Data    ____|__/    X____X____X____X____X____X____X____X____X____X   \___
  35             |  Start   0    1    2    3    4    5    6    7    P   Stop
  36             Request by host
  37
  38 Start bit:  can be long as 300-350us.
  39 Request:    Host pulls Clock line down to request to send a command.
  40 Timing:     After Request keyboard pull up Data and down Clock line to low for start bit.
  41             After request host release Clock line once Data line becomes hi.
  42             Host writes a bit while Clock is hi and Keyboard reads while low.
  43 Stop bit:   Host releases or pulls up Data line to hi after 9th clock and waits for keyboard pull down the line to lo.
  44 */
  45 uint8_t ibm4704_send(uint8_t data)
  46 {
  47     bool parity = true; // odd parity
  48     ibm4704_error = 0;
  49
  50     /* Request to send */
  51     idle();
  52     clock_lo();
  53
  54     /* wait for Start bit(Clock:lo/Data:hi) */
  55     WAIT(data_hi, 300, 0x30);
  56
  57     /* Data bit */
  58     for (uint8_t i = 0; i < 8; i++) {
  59         WAIT(clock_hi, 100, 0x40+i);
  60         //_delay_us(5);
  61         if (data&(1<<i)) {
  62             parity = !parity;
  63             data_hi();
  64         } else {
  65             data_lo();
  66         }
  67         WAIT(clock_lo, 100, 0x48+i);
  68     }
  69
  70     /* Parity bit */
  71     WAIT(clock_hi, 100, 0x34);
  72     if (parity) { data_hi(); } else { data_lo(); }
  73     WAIT(clock_lo, 100, 0x35);
  74
  75     /* Stop bit */
  76     WAIT(clock_hi, 100, 0x34);
  77     data_hi();
  78
  79     /* End */
  80     WAIT(data_lo, 100, 0x36);
  81
  82     inhibit();
  83     _delay_us(200); // wait to recover clock to hi
  84     return 0;
  85 ERROR:
  86     inhibit();
  87     if (ibm4704_error >= 0x30) {
  88         xprintf("x%02X ", ibm4704_error);
  89     }
  90     _delay_us(200); // wait to recover clock to hi
  91     return -1;
  92 }
  93
  94 /* receive data when host want else inhibit communication */
  95 uint8_t ibm4704_recv_response(void)
  96 {
  97     // 250 * 100us(wait start bit in ibm4704_recv)
  98     uint8_t data = 0;
  99     uint8_t try = 250;
 100     do {
 101         data = ibm4704_recv();
 102     } while (try-- && ibm4704_error);
 103     return data;
 104 }
 105
 106 /*
 107 Keyboard to Host
 108 ----------------
 109 Data bits are LSB first and Parity is odd. Clock has around 60us high and 30us low part.
 110
 111         ____      __   __   __   __   __   __   __   __   __   ________
 112 Clock       \____/  \_/  \_/  \_/  \_/  \_/  \_/  \_/  \_/  \_/
 113              ____ ____ ____ ____ ____ ____ ____ ____ ____ ____
 114 Data    ____/    X____X____X____X____X____X____X____X____X____X________
 115             Start   0    1    2    3    4    5    6    7    P  Stop
 116
 117 Start bit:  can be long as 300-350us.
 118 Inhibit:    Pull Data line down to inhibit keyboard to send.
 119 Timing:     Host reads bit while Clock is hi.
 120 Stop bit:   Keyboard pulls down Data line to lo after 9th clock.
 121 */
 122 uint8_t ibm4704_recv(void)
 123 {
 124     uint8_t data = 0;
 125     bool parity = true;    // odd parity
 126     ibm4704_error = IBM4704_ERR_NONE;
 127
 128     idle();
 129     _delay_us(5);   // wait for line settles
 130
 131     /* start bit */
 132     WAIT(clock_lo, 100, 0x11); // wait for keyboard to send
 133     WAIT(data_hi, 100, 0x12);  // can be delayed that long
 134
 135     WAIT(clock_hi, 100, 0x13); // first rising edge which can take longer
 136     /* data */
 137     for (uint8_t i = 0; i < 8; i++) {
 138         WAIT(clock_hi, 100, 0x20+i);
 139         //_delay_us(5);
 140         if (data_in()) {
 141             parity = !parity;
 142             data |= (1<<i);
 143         }
 144         WAIT(clock_lo, 150, 0x28+i);
 145     }
 146
 147     /* parity */
 148     WAIT(clock_hi, 100, 0x17);
 149     if (data_in() != parity) {
 150         ibm4704_error = IBM4704_ERR_PARITY;
 151         goto ERROR;
 152     }
 153     WAIT(clock_lo, 150, 0x18);
 154
 155     /* stop bit */
 156     WAIT(clock_hi, 100, 0x19);
 157     WAIT(data_lo, 1, 0x19);
 158
 159     inhibit();
 160     _delay_us(200); // wait to recover clock to hi
 161     return data;
 162 ERROR:
 163     if (ibm4704_error > 0x12) {
 164         xprintf("x%02X ", ibm4704_error);
 165     }
 166     inhibit();
 167     _delay_us(200); // wait to recover clock to hi
 168     return -1;
 169 }