adb.c

   1 #include <stdbool.h>
   2 #include <util/delay.h>
   3 #include <avr/io.h>
   4 #include "adb.h"
   5
   6
   7 static inline void data_lo(void);
   8 static inline void data_hi(void);
   9 static inline bool data_in(void);
  10 #ifdef ADB_PSW_BIT
  11 static inline void psw_lo(void);
  12 static inline void psw_hi(void);
  13 static inline bool psw_in(void);
  14 #endif
  15
  16 static inline void attention(void);
  17 static inline void place_bit0(void);
  18 static inline void place_bit1(void);
  19 static inline void send_byte(uint8_t data);
  20 static inline bool read_bit(void);
  21 static inline uint8_t read_byte(void);
  22 static inline uint8_t wait_data_lo(uint8_t us);
  23 static inline uint8_t wait_data_hi(uint8_t us);
  24
  25
  26 void adb_host_init(void)
  27 {
  28     data_hi();
  29 #ifdef ADB_PSW_BIT
  30     psw_hi();
  31 #endif
  32 }
  33
  34 #ifdef ADB_PSW_BIT
  35 bool adb_host_psw(void)
  36 {
  37     return psw_in();
  38 }
  39 #endif
  40
  41 uint16_t adb_host_kbd_recv(void)
  42 {
  43     uint16_t data = 0;
  44     attention();
  45     send_byte(0x2C);            // Addr:Keyboard(0010), Cmd:Talk(11), Register0(00)
  46     place_bit0();               // Stopbit(0)
  47     if (!wait_data_lo(0xFF))    // Tlt/Stop to Start(140-260us)
  48         return 0;               // No data to send
  49     if (!read_bit())            // Startbit(1)
  50         return -2;
  51     data = read_byte();
  52     data = (data<<8) | read_byte();
  53     if (read_bit())             // Stopbit(0)
  54         return -3;
  55     return data;
  56 }
  57
  58 // send state of LEDs
  59 void adb_host_kbd_led(uint8_t led)
  60 {
  61     attention();
  62     send_byte(0x2A);            // Addr:Keyboard(0010), Cmd:Listen(10), Register2(10)
  63     place_bit0();               // Stopbit(0)
  64     _delay_us(200);             // Tlt/Stop to Start
  65     place_bit1();               // Startbit(1)
  66     send_byte(0);               // send upper byte (not used)
  67     send_byte(led&0x07);        // send lower byte (bit2: ScrollLock, bit1: CapsLock, bit0: NumLock)
  68     place_bit0();               // Stopbit(0);
  69 }
  70
  71
  72 static inline void data_lo()
  73 {
  74     ADB_DDR  |=  (1<<ADB_DATA_BIT);
  75     ADB_PORT &= ~(1<<ADB_DATA_BIT);
  76 }
  77 static inline void data_hi()
  78 {
  79     ADB_PORT |=  (1<<ADB_DATA_BIT);
  80     ADB_DDR  &= ~(1<<ADB_DATA_BIT);
  81 }
  82 static inline bool data_in()
  83 {
  84     ADB_PORT |=  (1<<ADB_DATA_BIT);
  85     ADB_DDR  &= ~(1<<ADB_DATA_BIT);
  86     return ADB_PIN&(1<<ADB_DATA_BIT);
  87 }
  88
  89 #ifdef ADB_PSW_BIT
  90 static inline void psw_lo()
  91 {
  92     ADB_DDR  |=  (1<<ADB_PSW_BIT);
  93     ADB_PORT &= ~(1<<ADB_PSW_BIT);
  94 }
  95 static inline void psw_hi()
  96 {
  97     ADB_PORT |=  (1<<ADB_PSW_BIT);
  98     ADB_DDR  &= ~(1<<ADB_PSW_BIT);
  99 }
 100 static inline bool psw_in()
 101 {
 102     ADB_PORT |=  (1<<ADB_PSW_BIT);
 103     ADB_DDR  &= ~(1<<ADB_PSW_BIT);
 104     return ADB_PIN&(1<<ADB_PSW_BIT);
 105 }
 106 #endif
 107
 108 static inline void attention(void)
 109 {
 110     data_lo();
 111     _delay_us(700);
 112     place_bit1();
 113 }
 114
 115 static inline void place_bit0(void)
 116 {
 117     data_lo();
 118     _delay_us(65);
 119     data_hi();
 120     _delay_us(35);
 121 }
 122
 123 static inline void place_bit1(void)
 124 {
 125     data_lo();
 126     _delay_us(35);
 127     data_hi();
 128     _delay_us(65);
 129 }
 130
 131 static inline void send_byte(uint8_t data)
 132 {
 133     for (int i = 0; i < 8; i++) {
 134         if (data&(0x80>>i))
 135             place_bit1();
 136         else
 137             place_bit0();
 138     }
 139 }
 140
 141 static inline bool read_bit(void)
 142 {
 143     // ADB Bit Cells
 144     //
 145     // bit0: ______~~~
 146     //       65    :35us
 147     //
 148     // bit1: ___~~~~~~
 149     //       35 :65us
 150     //
 151     // bit0 low time: 60-70% of bit cell(42-91us)
 152     // bit1 low time: 30-40% of bit cell(21-52us)
 153     // bit cell time: 70-130us
 154     // [from Apple IIgs Hardware Reference Second Edition]
 155     //
 156     // After 55us if data line is low/high then bit is 0/1.
 157     // Too simple to rely on?
 158     bool bit;
 159     wait_data_lo(75);   // wait the beginning of bit cell
 160     _delay_us(55);
 161     bit = data_in();
 162     wait_data_hi(36);   // wait high part of bit cell
 163     return bit;
 164 }
 165
 166 static inline uint8_t read_byte(void)
 167 {
 168     uint8_t data = 0;
 169     for (int i = 0; i < 8; i++) {
 170         data <<= 1;
 171         if (read_bit())
 172             data = data | 1;
 173     }
 174     return data;
 175 }
 176
 177 static inline uint8_t wait_data_lo(uint8_t us)
 178 {
 179     while (data_in() && us) {
 180         _delay_us(1);
 181         us--;
 182     }
 183     return us;
 184 }
 185
 186 static inline uint8_t wait_data_hi(uint8_t us)
 187 {
 188     while (!data_in() && us) {
 189         _delay_us(1);
 190         us--;
 191     }
 192     return us;
 193 }