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:2, Cmd:talk(11), Reg:0(00)
  46     place_bit0();               // Stopbit
  47     if (!wait_data_lo(0xFF))    // 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
  59 static inline void data_lo()
  60 {
  61     ADB_DDR  |=  (1<<ADB_DATA_BIT);
  62     ADB_PORT &= ~(1<<ADB_DATA_BIT);
  63 }
  64 static inline void data_hi()
  65 {
  66     ADB_PORT |=  (1<<ADB_DATA_BIT);
  67     ADB_DDR  &= ~(1<<ADB_DATA_BIT);
  68 }
  69 static inline bool data_in()
  70 {
  71     ADB_PORT |=  (1<<ADB_DATA_BIT);
  72     ADB_DDR  &= ~(1<<ADB_DATA_BIT);
  73     return ADB_PIN&(1<<ADB_DATA_BIT);
  74 }
  75
  76 #ifdef ADB_PSW_BIT
  77 static inline void psw_lo()
  78 {
  79     ADB_DDR  |=  (1<<ADB_PSW_BIT);
  80     ADB_PORT &= ~(1<<ADB_PSW_BIT);
  81 }
  82 static inline void psw_hi()
  83 {
  84     ADB_PORT |=  (1<<ADB_PSW_BIT);
  85     ADB_DDR  &= ~(1<<ADB_PSW_BIT);
  86 }
  87 static inline bool psw_in()
  88 {
  89     ADB_PORT |=  (1<<ADB_PSW_BIT);
  90     ADB_DDR  &= ~(1<<ADB_PSW_BIT);
  91     return ADB_PIN&(1<<ADB_PSW_BIT);
  92 }
  93 #endif
  94
  95 static inline void attention(void)
  96 {
  97     data_lo();
  98     _delay_us(700);
  99     place_bit1();
 100 }
 101
 102 static inline void place_bit0(void)
 103 {
 104     data_lo();
 105     _delay_us(65);
 106     data_hi();
 107     _delay_us(35);
 108 }
 109
 110 static inline void place_bit1(void)
 111 {
 112     data_lo();
 113     _delay_us(35);
 114     data_hi();
 115     _delay_us(65);
 116 }
 117
 118 static inline void send_byte(uint8_t data)
 119 {
 120     for (int i = 0; i < 8; i++) {
 121         if (data&(0x80>>i))
 122             place_bit1();
 123         else
 124             place_bit0();
 125     }
 126 }
 127
 128 static inline bool read_bit(void)
 129 {
 130     // ADB Bit Cells
 131     //
 132     // bit0: ______~~~
 133     //       65    :35us
 134     //
 135     // bit1: ___~~~~~~
 136     //       35 :65us
 137     //
 138     // bit0 low time: 60-70% of bit cell(42-91us)
 139     // bit1 low time: 30-40% of bit cell(21-52us)
 140     // bit cell time: 70-130us
 141     // [from Apple IIgs Hardware Reference Second Edition]
 142     //
 143     // After 55us if data line is low/high then bit is 0/1.
 144     // Too simple to rely on?
 145     bool bit;
 146     wait_data_lo(75);   // wait the beginning of bit cell
 147     _delay_us(55);
 148     bit = data_in();
 149     wait_data_hi(36);   // wait high part of bit cell
 150     return bit;
 151 }
 152
 153 static inline uint8_t read_byte(void)
 154 {
 155     uint8_t data = 0;
 156     for (int i = 0; i < 8; i++) {
 157         data <<= 1;
 158         if (read_bit())
 159             data = data | 1;
 160     }
 161     return data;
 162 }
 163
 164 static inline uint8_t wait_data_lo(uint8_t us)
 165 {
 166     while (data_in() && us) {
 167         _delay_us(1);
 168         us--;
 169     }
 170     return us;
 171 }
 172
 173 static inline uint8_t wait_data_hi(uint8_t us)
 174 {
 175     while (!data_in() && us) {
 176         _delay_us(1);
 177         us--;
 178     }
 179     return us;
 180 }