summaryrefslogtreecommitdiffstats
path: root/protocol/ibm4704.c
blob: 26441ed52f300255f0bdb7f5336ccfa69ac6bb0b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
/*
Copyright 2010,2011,2012,2013 Jun WAKO <wakojun@gmail.com>
*/
#include <stdbool.h>
#include <util/delay.h>
#include "debug.h"
#include "ibm4704.h"


#define WAIT(stat, us, err) do { \
    if (!wait_##stat(us)) { \
        ibm4704_error = err; \
        goto ERROR; \
    } \
} while (0)


uint8_t ibm4704_error = 0;


void ibm4704_init(void)
{
    // POR
    //_delay_ms(2500);
    //while ( 0xA3 != ibm4704_recv() ) ;

    inhibit();
    DDRD |= 1<<3;
    PORTD &= ~(1<<3);
}

uint8_t ibm4704_send(uint8_t data)
{
    bool parity = true; // odd parity
    ibm4704_error = 0;

    /* Request to send */
    idle();
    clock_lo();
PIND |= 1<<3;

    /* wait for Start bit(Clock:lo/Data:hi) */
    WAIT(data_hi, 300, 0x30);

    /* Data bit */
    for (uint8_t i = 0; i < 8; i++) {
        WAIT(clock_hi, 100, 0x31);
        //_delay_us(5);
PIND |= 1<<3;
        if (data&(1<<i)) {
            parity = !parity;
            data_hi();
        } else {
            data_lo();
        }
        WAIT(clock_lo, 100, 0x32);
    }

    /* Parity bit */
    WAIT(clock_hi, 100, 4);
PIND |= 1<<3;
    if (parity) { data_hi(); } else { data_lo(); }
    WAIT(clock_lo, 100, 5);

    /* Stop bit */
    WAIT(clock_hi, 100, 4);
    data_hi();

    /* End */
    WAIT(data_lo, 100, 6);

    inhibit();
    _delay_us(200); // wait to recover clock to hi
    return 0;
ERROR:
    inhibit();
xprintf("x%02X ", ibm4704_error);
    _delay_us(200); // wait to recover clock to hi
    return -1;
}

/* receive data when host want else inhibit communication */
uint8_t ibm4704_recv_response(void)
{
    // 250 * 100us(wait start bit in ibm4704_recv)
    uint8_t data = 0;
    uint8_t try = 250;
    do {
        data = ibm4704_recv();
    } while (try-- && ibm4704_error);
    return data;
}

/*
Keyboard to Host:
Clock   ~~~~___~~_~~_~~_~~_~~_~~_~~_~~_~~_~~~~~~~~ H:60us/L:30us

Data    ____~~X==X==X==X==X==X==X==X==X==X________
            |  0  1  2  3  4  5  6  7  P(odd)
            |  LSB                MSB
            Start bit(80us)
*/
uint8_t ibm4704_recv(void)
{
    uint8_t data = 0;
    bool parity = true;    // odd parity
    ibm4704_error = IBM4704_ERR_NONE;

    idle();
    _delay_us(5);   // wait for line settles

    /* start bit */
    WAIT(clock_lo, 100, 1); // wait for keyboard to send
    WAIT(data_hi, 100, 2);  // can be delayed that long

    WAIT(clock_hi, 100, 3); // first rising edge which can take longer
    /* data */
    for (uint8_t i = 0; i < 8; i++) {
        WAIT(clock_hi, 100, 0x20+i);
        //_delay_us(5);
        if (data_in()) {
            parity = !parity;
            data |= (1<<i);
        }
        WAIT(clock_lo, 150, 0x28+i);
    }

    /* parity */
    WAIT(clock_hi, 100, 7);
    if (data_in() != parity) {
        ibm4704_error = IBM4704_ERR_PARITY;
        goto ERROR;
    }
    WAIT(clock_lo, 150, 8);

    /* stop bit */
    WAIT(clock_hi, 100, 9);
    WAIT(data_lo, 1, 9);

    inhibit();
    _delay_us(200); // wait to recover clock to hi
    return data;
ERROR:
    if (ibm4704_error > 2) {
        xprintf("x%02X ", ibm4704_error);
    }
    inhibit();
    _delay_us(200); // wait to recover clock to hi
    return -1;
}