tmk_core/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 "ring_buffer.h"
   8 #include "ibm4704.h"
   9
  10
  11 #define WAIT(stat, us, err) do { \
  12     if (!wait_##stat(us)) { \
  13         ibm4704_error = err; \
  14         goto ERROR; \
  15     } \
  16 } while (0)
  17
  18
  19 uint8_t ibm4704_error = 0;
  20
  21
  22 void ibm4704_init(void)
  23 {
  24     inhibit();  // keep keyboard from sending
  25     IBM4704_INT_INIT();
  26     IBM4704_INT_ON();
  27     idle();     // allow keyboard sending
  28 }
  29
  30 /*
  31 Host to Keyboard
  32 ----------------
  33 Data bits are LSB first and Parity is odd. Clock has around 60us high and 30us low part.
  34
  35         ____        __   __   __   __   __   __   __   __   __   ________
  36 Clock       \______/  \_/  \_/  \_/  \_/  \_/  \_/  \_/  \_/  \_/
  37             ^   ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ___
  38 Data    ____|__/    X____X____X____X____X____X____X____X____X____X   \___
  39             |  Start   0    1    2    3    4    5    6    7    P   Stop
  40             Request by host
  41
  42 Start bit:  can be long as 300-350us.
  43 Request:    Host pulls Clock line down to request to send a command.
  44 Timing:     After Request keyboard pull up Data and down Clock line to low for start bit.
  45             After request host release Clock line once Data line becomes hi.
  46             Host writes a bit while Clock is hi and Keyboard reads while low.
  47 Stop bit:   Host releases or pulls up Data line to hi after 9th clock and waits for keyboard pull down the line to lo.
  48 */
  49 uint8_t ibm4704_send(uint8_t data)
  50 {
  51     bool parity = true; // odd parity
  52     ibm4704_error = 0;
  53
  54     IBM4704_INT_OFF();
  55
  56     /* Request to send */
  57     idle();
  58     clock_lo();
  59
  60     /* wait for Start bit(Clock:lo/Data:hi) */
  61     WAIT(data_hi, 300, 0x30);
  62
  63     /* Data bit */
  64     for (uint8_t i = 0; i < 8; i++) {
  65         WAIT(clock_hi, 100, 0x40+i);
  66         if (data&(1<<i)) {
  67             parity = !parity;
  68             data_hi();
  69         } else {
  70             data_lo();
  71         }
  72         WAIT(clock_lo, 100, 0x48+i);
  73     }
  74
  75     /* Parity bit */
  76     WAIT(clock_hi, 100, 0x34);
  77     if (parity) { data_hi(); } else { data_lo(); }
  78     WAIT(clock_lo, 100, 0x35);
  79
  80     /* Stop bit */
  81     WAIT(clock_hi, 100, 0x34);
  82     data_hi();
  83
  84     /* End */
  85     WAIT(data_lo, 100, 0x36);
  86
  87     idle();
  88     IBM4704_INT_ON();
  89     return 0;
  90 ERROR:
  91     idle();
  92     if (ibm4704_error > 0x30) {
  93         xprintf("S:%02X ", ibm4704_error);
  94     }
  95     IBM4704_INT_ON();
  96     return -1;
  97 }
  98
  99 /* wait forever to receive data */
 100 uint8_t ibm4704_recv_response(void)
 101 {
 102     while (!rbuf_has_data()) {
 103         _delay_ms(1);
 104     }
 105     return rbuf_dequeue();
 106 }
 107
 108 uint8_t ibm4704_recv(void)
 109 {
 110     if (rbuf_has_data()) {
 111         return rbuf_dequeue();
 112     } else {
 113         return -1;
 114     }
 115 }
 116
 117 /*
 118 Keyboard to Host
 119 ----------------
 120 Data bits are LSB first and Parity is odd. Clock has around 60us high and 30us low part.
 121
 122         ____       __   __   __   __   __   __   __   __   __   _______
 123 Clock       \_____/  \_/  \_/  \_/  \_/  \_/  \_/  \_/  \_/  \_/
 124              ____ ____ ____ ____ ____ ____ ____ ____ ____ ____
 125 Data    ____/    X____X____X____X____X____X____X____X____X____X________
 126             Start   0    1    2    3    4    5    6    7    P  Stop
 127
 128 Start bit:  can be long as 300-350us.
 129 Inhibit:    Pull Data line down to inhibit keyboard to send.
 130 Timing:     Host reads bit while Clock is hi.(rising edge)
 131 Stop bit:   Keyboard pulls down Data line to lo after 9th clock.
 132 */
 133 ISR(IBM4704_INT_VECT)
 134 {
 135     static enum {
 136         BIT0, BIT1, BIT2, BIT3, BIT4, BIT5, BIT6, BIT7, PARITY, STOP
 137     } state = BIT0;
 138     // LSB first
 139     static uint8_t data = 0;
 140     // Odd parity
 141     static uint8_t parity = false;
 142
 143     ibm4704_error = 0;
 144
 145     switch (state) {
 146         case BIT0:
 147         case BIT1:
 148         case BIT2:
 149         case BIT3:
 150         case BIT4:
 151         case BIT5:
 152         case BIT6:
 153         case BIT7:
 154             data >>= 1;
 155             if (data_in()) {
 156                 data |= 0x80;
 157                 parity = !parity;
 158             }
 159             break;
 160         case PARITY:
 161             if (data_in()) {
 162                 parity = !parity;
 163             }
 164             if (!parity)
 165                 goto ERROR;
 166             break;
 167         case STOP:
 168             // Data:Low
 169             WAIT(data_lo, 100, state);
 170             rbuf_enqueue(data);
 171             ibm4704_error = IBM4704_ERR_NONE;
 172             goto DONE;
 173             break;
 174         default:
 175             goto ERROR;
 176     }
 177     state++;
 178     goto RETURN;
 179 ERROR:
 180     ibm4704_error = state;
 181     while (ibm4704_send(0xFE)) _delay_ms(1); // resend
 182     xprintf("R:%02X%02X\n", state, data);
 183 DONE:
 184     state = BIT0;
 185     data = 0;
 186     parity = false;
 187 RETURN:
 188     return;
 189 }